TIME DELAY DEVICE AND PHASED ARRAY ANTENNA

Abstract

The present invention provides a time delay device which allows changing, in accordance with a frequency of a local signal, a delay in a radio frequency signal supplied to an antenna element and also allows reducing a degree of dependency of the delay on a radio frequency in a band which is used. Each of (i) dispersion caused by a first dispersion imparting filter which gives a delay to a first local signal and (ii) dispersion caused by a second dispersion imparting filter which gives a delay to an intermediate frequency signal generated from the first local signal and the radio frequency signal is set to have a positive or negative sign which is opposite to the sign of the other.

Claims

1. A time delay device, comprising: a first transmission line which generates a second local signal V.sub.LO′(t)=V.sub.LO(t−θ.sub.1) by imparting a delay θ.sub.1 to a first local signal V.sub.LO(t) having a frequency f.sub.LO; a first mixer which generates a first intermediate frequency signal V.sub.IF(t) having a frequency f.sub.RF−f.sub.LO, by multiplying a first radio frequency signal V.sub.RF(t) having a frequency f.sub.RF(f.sub.LO<f.sub.RF) by the second local signal V.sub.LO′(t); a second transmission line on which a first dispersion imparting filter is inserted, the second transmission line generating a third local signal V.sub.LO″(t)=V.sub.LO(t−θ.sub.D−θ.sub.2) by imparting, to the first local signal V.sub.LO(t), a delay θ.sub.D by the first dispersion imparting filter and a delay θ.sub.2 by the second transmission line; a third transmission line on which a second dispersion imparting filter is inserted, the second dispersion imparting filter imparting dispersion of opposite sign to dispersion imparted by the first dispersion imparting filter, the third transmission line generating a second intermediate frequency signal V.sub.IF′(t)=V.sub.IF(t−θ.sub.D′−θ.sub.3) by imparting, to the first intermediate frequency signal V.sub.IF(t), a delay θ.sub.D′ by the second dispersion imparting filter and a delay θ.sub.3 by the third transmission line; and a second mixer which generates a second radio frequency signal V.sub.RF′(t) having the frequency f.sub.RF, by multiplying the third local signal V.sub.LO″(t) by the second intermediate frequency signal V.sub.IF′(t).

2. The time delay device as set forth in claim 1, wherein the second transmission line has an electrical length equal to a sum of an electrical length of the first transmission line and an electrical length of the third transmission line.

3. The time delay device as set forth in claim 1, wherein each of the first dispersion imparting filter and the second dispersion imparting filter is constituted by a CEBG (Chirped Electromagnetic Bandgap) transmission line.

4. The time delay device as set forth in claim 1, wherein a third dispersion imparting filter which imparts dispersion of opposite sign to the dispersion imparted by the second dispersion imparting filter is inserted on (i) a transmission line that transmits the first radio frequency signal V.sub.RF(t) supplied to the first mixer or (ii) a transmission line that transmits the second radio frequency signal V.sub.RF′(t) outputted from the second mixer.

5. A phased array antenna comprising: n (n is an integer of 2 or more) antenna elements A1 through An; and n time delay devices TD11 through TD1n, each time delay device TD1i (i=1 to n) having a configuration of a time delay device recited in claim 1, the second radio frequency signal generated by the each time delay device TD1i being supplied to a corresponding antenna element Ai.

6. The phased array antenna as set forth in claim 5, wherein the first local signal supplied to the each time delay device TD1i has a frequency which is set in accordance with a position of the corresponding antenna element Ai in an order in which the respective antenna elements Ai are provided, the frequencies of the respective time delay devices TD1i having an equal difference therebetween.

7. A phased array antenna comprising: n (n is an integer of 2 or more) antenna elements A1 through An; and n time delay devices TD21 through TD2n, each time delay device TD2i (i=1 to n) having a configuration of a time delay device recited in claim 1, a radio signal outputted from each antenna element Ai being supplied, as the first radio frequency signal, to a corresponding time delay device TD2i.

8. The phased array antenna as set forth in claim 7, wherein the first local signal supplied to the each time delay device TD2i has a frequency which is set in accordance with a position of a corresponding antenna element Ai in an order in which the respective antenna elements Ai are provided, the frequencies of the respective time delay devices TD2i having an equal difference therebetween.

9. A phased array antenna comprising: a fir phased array antenna, the first phased array antenna serving as a transmitting antenna; and a second phased array antenna, the second phased array antenna serving as a receiving antenna, wherein the first phased array antenna comprising: n (n is an integer of 2 or more) antenna elements A1 through An; and n time delay devices TD11 through TD1n, each time delay device TD1i (i=1 to n) having a configuration of a time delay device recited in claim 1, the second radio frequency signal generated by the each time delay device TD1i being supplied to a corresponding antenna element Ai, wherein the second phased array antenna comprising: n (n is an integer of 2 or more) antenna elements A1 through An; and n time delay devices TD21 through TD2n, each time delay device TD2i (i=1 to n) having a configuration of a time delay device recited in claim 1, a radio signal outputted from each antenna element Ai being supplied, as the first radio frequency signal, to a corresponding time delay device TD2i, the antenna elements A1 through An being shared by the transmitting antenna and the receiving antenna.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0042] FIG. 1 is a block diagram showing a configuration of a time delay device in accordance with Embodiment 1 of the present invention.

[0043] FIG. 2 is a block diagram showing a configuration of a time delay device in accordance with Embodiment 2 of the present invention.

[0044] FIG. 3 is a block diagram showing a configuration of a time delay device in accordance with Embodiment 3 of the present invention.

[0045] FIG. 4 is a block diagram concerning Embodiment 4 of the present invention and showing a configuration of a transmitting phased array antenna which includes the time delay device in accordance with Embodiment 1.

[0046] FIG. 5 is a block diagram concerning Embodiment 5 of the present invention and showing a configuration of a receiving phased array antenna which includes the time delay device in accordance with Embodiment 1.

[0047] FIG. 6 is a block diagram concerning Embodiment 6 of the present invention and showing a configuration of a transmitting and receiving phased array antenna which is obtained by combining the transmitting phased array antenna shown in FIG. 4 and the receiving phased array antenna shown in FIG. 5.

[0048] FIG. 7 is a block diagram concerning Embodiment 7 of the present invention and showing a configuration of a transmitting phased array antenna which includes a modified example of the time delay device in accordance with Embodiment 1.

[0049] FIG. 8 is a block diagram concerning Embodiment 8 of the present invention and showing a configuration of a receiving phased array antenna which includes a modified example of the time delay device in accordance with Embodiment 1.

[0050] FIG. 9 is a block diagram concerning Embodiment 9 of the present invention and showing a configuration of a transmitting and receiving phased array antenna which is obtained by combining the transmitting phased array antenna shown in FIG. 4 and the receiving phased array antenna shown in FIG. 8.

[0051] FIG. 10 is a block diagram concerning Embodiment 10 of the present invention and showing a configuration of a transmitting and receiving phased array antenna which is obtained by combining the transmitting phased array antenna shown in FIG. 7 and the receiving phased array antenna shown in FIG. 5.

[0052] FIG. 11 is a block diagram concerning Embodiment 11 of the present invention and showing a configuration of a transmitting and receiving phased array antenna which is obtained by combining the transmitting phased array antenna shown in FIG. 7 and the receiving phased array antenna shown in FIG. 8.

[0053] FIG. 12 is a view illustrating a principle of controlling a main beam direction of a radio wave transmitted and received by a phased array antenna.

[0054] FIG. 13 is a block diagram showing an example configuration of a conventional transmitting phased array antenna.

[0055] FIG. 14 is a block diagram showing an example configuration of a conventional receiving phased array antenna.

[0056] FIG. 15 is a block diagram showing an example configuration of a conventional transmitting and receiving phased array antenna.

[0057] FIG. 16 is a block diagram showing an example configuration of a conventional time delay device.

[0058] FIG. 17 is a block diagram showing another example configuration of a conventional time delay device.

DESCRIPTION OF EMBODIMENTS

Embodiment 1

[0059] (Configuration of Time Delay Device)

[0060] The following description will discuss, with reference to FIG. 1, a time delay device 1 in accordance with Embodiment 1 of the present invention. FIG. 1 is a block diagram showing a configuration of the time delay device 1. The time delay device 1 can be provided in any of a transmitting phased array antenna, a receiving phased array antenna, and a transmitting and receiving phased array antenna. This point also applies to each of time delay devices in accordance with other embodiments, which will be described later.

[0061] As shown in FIG. 1, the time delay device 1 includes two mixers MX1 and MX2 (a first mixer and a second mixer, respectively), two circulators C1 and C2, and two dispersion imparting filters DF1 and DF2 (a first dispersion imparting filter and a second dispersion imparting filter, respectively). The circulators C1 and C2 function in a manner as described above with reference to FIG. 15.

[0062] The mixer MX1 has two input terminals, of which a first input terminal is connected to a radio frequency signal source RF which generates a first radio frequency signal V.sub.RF(t) having a frequency f.sub.RF (f.sub.LO<f.sub.RF). A second input terminal of the two input terminals of the mixer MX1 is connected to a first transmission line TL1. The first transmission line TL1 is a line that extends from an output terminal of a local signal source LO, which generates a first local signal V.sub.LO(t) having a frequency f.sub.LO, to the second input terminal of the mixer MX1. The first transmission line TL1 generates a second local signal V.sub.LO′(t)−V.sub.LO(t−θ1) by imparting a line delay θ.sub.1 to the first local signal V.sub.LO(t) generated by the local signal source LO.

[0063] The mixer MX2 has two input terminals, of which a first input terminal is connected to a second transmission line TL2 on which the dispersion imparting filter DF1 is inserted. The second transmission line TL2 is a line that extends so as to start from the output terminal of the local signal source LO, pass through a first port and a second port of the circulator C1, go to and return from the dispersion imparting filter DF1, pass through the second port and a third port of the circulator C1, and then reach the first input terminal of the mixer MX2. The second transmission line TL2 generates a third local signal V.sub.LO″(t)=V.sub.LO(t−θ.sub.D−θ.sub.2) by imparting, to the first local signal V.sub.LO(t) generated by the local signal source LO, a line delay θ.sub.2 and a delay θ.sub.D which is caused by the dispersion imparting filter DF1.

[0064] In a case where a dispersion imparting filter that imparts negative dispersion −D [s/Hz] is used as the dispersion imparting filter DF1, the delay θ.sub.D imparted to the first local signal V.sub.LO(t) is θ.sub.D=Df.sub.LO+θ.sub.0, and the third local signal V.sub.LO″(t) is V.sub.LO″(t)=V.sub.LO(t−Df.sub.LO−θ.sub.0−θ.sub.2). Meanwhile, in a case where a dispersion imparting filter that imparts positive dispersion +D [s/Hz] is used as the dispersion imparting filter DF1, the delay θ.sub.D imparted to the first local signal V.sub.LO(t) is θ.sub.D=−Df.sub.LO+θ.sub.0, and the third local signal V.sub.LO″(t) is V.sub.LO′(t)=V.sub.LO(t+Df.sub.LO−θ.sub.0−θ.sub.2).

[0065] Note that the dispersion imparting filter DF1 as described above can be realized by use of, for example, a chirped electromagnetic bandgap (CEBG) transmission line as disclosed in Non-patent Literature 1. The CEBG transmission line is constituted by a microstrip line having a strip conductor whose width is periodically increased and reduced. Accordingly, a position on the CEBG transmission line from which position an input signal is reflected can be changed so as to change a line length of the CEBG transmission line, in accordance with a frequency of the input signal. This allows imparting a delay to the input signal in accordance with a frequency of the input signal.

[0066] A second input terminal of the mixer MX2 is connected to a third transmission line TL3 on which the dispersion imparting filter DF2 is inserted. The third transmission line TL3 is a line that extends so as to start from an output terminal of the mixer MX1, pass through a first port and a second port of the circulator C2, go to and return from the dispersion imparting filter DF2, pass through the second port and a third port of the circulator C2, and then reach the second input terminal of the mixer MX2. The third transmission line TL3 generates a second intermediate frequency signal V.sub.IF′(t)=V.sub.IF(t−θ.sub.D′−θ.sub.2) by imparting, to a first intermediate frequency signal V.sub.IF(t) generated by the mixer MX1, a line delay θ.sub.3 and a delay θ.sub.D′ which is caused by the dispersion imparting filter DF2.

[0067] As the dispersion imparting filter DF2, a dispersion imparting filter that imparts dispersion of equal absolute value and opposite sign to dispersion imparted by the dispersion imparting filter DF1. That is, in a case where a dispersion imparting filter that imparts negative dispersion −D [s/Hz] is used as the dispersion imparting filter DF1, a dispersion imparting filter that imparts positive dispersion +D [s/Hz] is used as the dispersion imparting filter DF2. Meanwhile, in a case where a dispersion imparting filter that imparts positive dispersion +D [s/Hz] is used as the dispersion imparting filter DF1, a dispersion imparting filter that imparts negative dispersion −D [s/Hz] is used as the dispersion imparting filter DF2.

[0068] In a case where the dispersion imparting filter DF2 has positive dispersion +D [s/Hz], the delay θ.sub.D′ imparted to the first intermediate frequency signal V.sub.IF(t) is OD′=−D(f.sub.RF−f.sub.LO)+θ.sub.0, and the second intermediate frequency signal V.sub.IF′(t) is V.sub.IF′(t)=V.sub.IF(t+D(f.sub.RF−f.sub.LO)−θ.sub.0−θ.sub.2). Meanwhile, in a case where the dispersion imparting filter DF2 has negative dispersion −D [s/Hz], the delay θ.sub.D′ imparted to the first intermediate frequency signal V.sub.IF(t) is θ.sub.D′=+D(f.sub.RF−f.sub.LO)+θ.sub.0, and the second intermediate frequency signal V.sub.IF′(t) is V.sub.IF′(t)=V.sub.IF(t−D(f.sub.RF−f.sub.LO)−θ.sub.0−θ.sub.2).

[0069] (Operation of Time Delay Device)

[0070] The following description will discuss an operation of the time delay device 1 having the configuration above in which operation the first radio frequency signal V.sub.RF(t) and the first local signal V.sub.LO(t) are supplied to the time delay device 1 and eventually the radio frequency signal V.sub.RF′(t) is outputted from the time delay device 1.

[0071] First, the first radio frequency signal V.sub.RF(t) generated by the radio frequency signal source RF and the first local signal V.sub.LO(t) generated by the local frequency signal source LO can be respectively represented by, for example, the following formulae (15) and (16).

[Math 15]

V.sub.RF(t)=V.sub.RF cos(2πf.sub.RFt)  (15)

[Math 16]

V.sub.LO(t)=V.sub.LO cos(2 πf.sub.LOt)  (16)

[0072] The first input terminal of the mixer MX1 is supplied with the first radio frequency signal V.sub.RF(t) generated by the radio frequency signal source RF. The second input terminal of the mixer MX1 is supplied with the second local signal V.sub.LO′(t) which is obtained by delaying, by the first transmission line TL1 described above, the first local signal V.sub.LO(t) generated by the local signal source LO. In a case where the first local signal V.sub.LO(t) is represented by the formula (16), the second local signal V.sub.LO′(t) is represented by the following formula (17).

[Math 17]

V.sub.LO′(t)=V.sub.LO cos(2πf.sub.LO(t−θ.sub.1))  (17)

[0073] The mixer MX1 generates the first intermediate frequency signal V.sub.IF(t) by multiplying the radio frequency signal V.sub.RF(t) by the second local signal V.sub.LO′(t) and then removing a high frequency component (down-converting the radio frequency signal V.sub.RF(t) with use of the second local signal V.sub.LO′(t)). In a case where the radio frequency signal V.sub.RF(t) and the second local signal V.sub.LO′(t) which are supplied to the mixer MX1 are respectively represented by the formulae (15) and (17), the first intermediate frequency signal V.sub.IF(t) generated by the mixer MX1 is represented by the following formula (18).

[00008]$\begin{array}{cc}\left[\mathrm{Math}.Math..Math.1.Math.8\right]& \\ V_{\mathrm{IF}}\left(t\right)=\frac{v_{\mathrm{RF}}.Math.v_{\mathrm{LO}}}{2}.Math.\cos \left(2.Math.\pi \left(f_{\mathrm{RF}}-f_{\mathrm{LO}}\right).Math.t+2.Math.\pi .Math..Math.f_{\mathrm{LO}}.Math.{\theta }_1\right)& \left(18\right)\end{array}$

[0074] The first input terminal of the mixer MX2 is supplied with the third local signal V.sub.LO″(t) which is obtained by delaying, by the second transmission line TL2, the first local signal V.sub.LO(t) generated by the local signal source LO. On the assumption that a dispersion imparting filter that imparts negative dispersion −D [s/Hz] is used as the dispersion imparting filter DF1 inserted in the second transmission line TL2, the third local signal V.sub.LO″(t) is represented by the following formula (19) in a case where the first local signal V.sub.LO(t) is represented by the formula (16).

[Math 19]

V.sub.LO″(t)=V.sub.LO cos(2πf.sub.LO(t−Df.sub.LO−θ.sub.0−θ.sub.2))  (19)

[0075] The second input terminal of the mixer MX2 is supplied with the second intermediate frequency signal V.sub.IF′(t) which is obtained by delaying, at the third transmission line TL3, the first intermediate frequency signal V.sub.IF(t) generated by the mixer MX1. On the assumption that a dispersion imparting filter that imparts positive dispersion +D [s/Hz] is used as the dispersion imparting filter DF2 inserted in the third transmission line TL3, the second intermediate frequency signal V.sub.IF′(t) is represented by the following formula (20) in a case where the first intermediate frequency signal V.sub.IF(t) is represented by the formula (18).

[00009]$\begin{array}{cc}.Math.\left[\mathrm{Math}.Math..Math.20\right]& \\ V_{\mathrm{IF}}^{\prime }\left(t\right)=\frac{v_{\mathrm{RF}}.Math.v_{\mathrm{LO}}}{2}.Math.\cos \left(2.Math.\pi \left(f_{\mathrm{RF}}-f_{\mathrm{LO}}\right).Math.\left\{t+D\left(f_{\mathrm{RF}}-f_{\mathrm{LO}}\right)-{\theta }_0-{\theta }_3\right\}+2.Math.\pi .Math..Math.f_{\mathrm{LO}}.Math.{\theta }_1\right)& \left(20\right)\end{array}$

[0076] The mixer MX2 generates the second radio frequency signal V.sub.RF′(t) by multiplying the second intermediate frequency signal V.sub.IF′(t) by the third local signal V.sub.LO″(t) and then removing a low frequency component (up-converting the second intermediate frequency signal V.sub.IF′(t) with use of the third local signal V.sub.LO′(t)). In a case where the second intermediate frequency signal V.sub.IF′(t) and the third local signal V.sub.LO′(t) which are supplied to the mixer MX2 are respectively represented by the formulae (20) and (19), the second radio frequency signal V.sub.RF′(t) generated by the mixer MX2 is represented by the following formula (21).

[00010]$\begin{array}{cc}.Math.\left[\mathrm{Math}.Math..Math.21\right]& \\ V_{\mathrm{RF}}^{\prime }\left(t\right)=\frac{V_{\mathrm{RF}}.Math.V_{\mathrm{LO}}^2}{4}.Math..Math.\cos (.Math.2.Math..Math.\pi .Math.\hspace{1em}.Math..Math.f_{\mathrm{RF}}[.Math.t-\hspace{1em}.Math.\hspace{1em}\hspace{1em}\left\{\left(\frac{{\theta }_2-\left({\theta }_1+{\theta }_3\right)}{f_{\mathrm{RF}}}+2.Math.D\right).Math.f_{\mathrm{LO}}-{\mathrm{Df}}_{\mathrm{RF}}+{\theta }_0+{\theta }_3\right\}])& \left(21\right)\end{array}$

[0077] From the formula (21), a delay δ of the second radio frequency signal V.sub.RF′(t) with respect to the first radio frequency signal V.sub.RF(t) is represented by the following formula (22).

[00011]$\begin{array}{cc}\left[\mathrm{Math}.Math..Math.22\right]& \\ \delta =\left(\frac{{\theta }_2-\left({\theta }_1+{\theta }_3\right)}{f_{\mathrm{RF}}}+2.Math.D\right).Math.f_{\mathrm{LO}}-{\mathrm{Df}}_{\mathrm{RF}}+{\theta }_0+{\theta }_3& \left(22\right)\end{array}$

[0078] From the formula (22), the following matters are drawn. That is, according to the time delay device 1, it is possible to change the delay δ freely in accordance with the frequency f.sub.LO of the first local signal V.sub.LO(t). Furthermore, in the time delay device 1, an amount of change Δf.sub.LO in frequency f.sub.LO, which is a control variable, of the local signal V.sub.LO(t) and an amount of change Δδ in delay δ, which is a controlled variable, are in a relation: Δδ={(θ.sub.2−θ.sub.1−θ.sub.3)/f.sub.RF−2D}Δf.sub.LO or a relation: Δδ={(θ.sub.2−θ.sub.1−θ.sub.3)/f.sub.RF+2D}Δf.sub.LO. Accordingly, as an electrical length of the second transmission line TL2 is approximated to a sum of an electrical length of the first transmission line TL1 and an electrical length of the third transmission line TL3 so that θ.sub.2−θ.sub.1−θ.sub.3 is approximated to 0, a degree of dependency of the amount of change Δδ in delay δ on the frequency f.sub.RF of the radio frequency signal V.sub.RF(t) can be reduced to whatever extent. In particular, in a case where the electrical length of the second transmission line TL2 is made to coincide with the sum of the electrical length of the first transmission line TL1 and the electrical length of the third transmission line TL3 so that θ.sub.2−θ.sub.1−θ.sub.3=0, the amount of change Δδ in delay δ does not depend on the frequency f.sub.RF of the radio frequency signal V.sub.RF(t). This facilitates, as compared with a conventional technique, the control of the delay δ in which control the frequency f.sub.LO of the local signal V.sub.LO(t) is a control variable.

[0079] The description above dealt with an operation in a case where the dispersion imparting filter that imparts negative dispersion −D [s/Hz] is used as the dispersion imparting filter DF1 and the dispersion imparting filter that imparts positive dispersion +D [s/Hz] is used as the dispersion imparting filter DF2. Note, however, that the present invention is not limited to this. That is, the dispersion imparting filter DF1 can be a dispersion imparting filter that imparts positive dispersion +D [s/Hz], and the dispersion imparting filter DF2 can be a dispersion imparting filter that imparts negative dispersion −D [s/Hz]. In this case, the delay δ is represented by the following formula (23), and an advantageous effect completely identical to the previously discussed advantageous effect is provided.

[00012]$\begin{array}{cc}\left[\mathrm{Math}.Math..Math.23\right]& \\ \delta =\left(\frac{{\theta }_2-\left({\theta }_1+{\theta }_3\right)}{f_{\mathrm{RF}}}+2.Math.D\right).Math.f_{\mathrm{LO}}+{\mathrm{Df}}_{\mathrm{RF}}+{\theta }_0+{\theta }_3& \left(23\right)\end{array}$

Embodiment 2

[0080] (Configuration of Time Delay Device)

[0081] The following description will discuss, with reference to FIG. 2, a configuration of a time delay device 2 in accordance with Embodiment 2 of the present invention. FIG. 2 is a block diagram showing a configuration of the time delay device 2. For easy explanation, the same reference signs will be given to configurations each having the same function as a configuration described in Embodiment 1, and descriptions on such a configuration will be omitted.

[0082] As shown in FIG. 2, the time delay device 2 further includes, in addition to the configuration of the time delay device 1, a circulator C3 and a dispersion imparting filter DF3 which are provided on an output side of a mixer MX2, that is, on a transmission line to which a second radio frequency signal V.sub.RF′(t) is outputted from the mixer MX2. The mixer MX2 has an output terminal which is connected to a first port among three ports of the circulator C3, and a second port of the circulator C3 is connected to the dispersion imparting filter DF3.

[0083] Dispersion imparted by the dispersion imparting filter DF3 is set to be of opposite sign to dispersion imparted by the dispersion imparting filter DF2. That is, in a case where the dispersion imparting filter DF2 imparts positive dispersion +D [s/Hz], the dispersion imparting filter DF3 imparts negative dispersion −D [s/Hz], and in a case where the dispersion imparting filter DF2 imparts negative dispersion −D [s/Hz], the dispersion imparting filter DF3 imparts positive dispersion +D [s/Hz].

[0084] Accordingly, a third radio frequency signal V.sub.RF″(t) which is obtained by correcting a delay included in the second radio frequency signal V.sub.RF′(t) and therefore has a more appropriate delay is outputted from a third port of the circulator C3.

[0085] (Operation of Time Delay Device)

[0086] A reason why the time delay device 2 is capable of generating the third radio frequency signal V.sub.RF″(t) having the more appropriate delay is as follows. The second radio frequency signal V.sub.RF′(t) has a frequency which is f.sub.RF based on the formula (21). Accordingly, in a case where the dispersion imparting filter DF2 imparts positive dispersion +D [s/Hz] and the dispersion imparting filter DF3 imparts negative dispersion −D [s/Hz], V.sub.RF″(t)=V.sub.RF′(t−Df.sub.RF). It is thus possible to cancel a term Df.sub.RF included in the delay δ in the formula (22).

[0087] As such, when θ.sub.2−(θ.sub.1+θ.sub.3)=0, it is possible to generate a delay δ that does not contain the frequency f.sub.RF at all. In this case, the time delay device 2 is able to generate an optimum delay δ that fluctuates in proportion to a frequency f.sub.LO of a first local signal V.sub.LO(t).

Embodiment 3

[0088] (Configuration of Time Delay Device)

[0089] The following description will discuss, with reference to FIG. 3, a configuration of a time delay device 3 in accordance with Embodiment 3 of the present invention. FIG. 3 is a block diagram showing a configuration of the time delay device 3. For easy explanation, the same reference signs will be given to configurations each having the same function as a configuration described in Embodiments 1 and 2, and descriptions on such a configuration will be omitted.

[0090] As shown in FIG. 3, the time delay device 3 further includes, in addition to the configuration of the time delay device 1, a circulator C4 and a dispersion imparting filter DF4 which are provided on an input side of a mixer MX1, that is, on a transmission line which supplies a first radio frequency signal V.sub.RF(t) to the mixer MX1. The circulator C4 has three ports, of which a first port is supplied with the first radio frequency signal V.sub.RF(t), a second port is connected to the dispersion imparting filter DF4, and a third port is connected to a first input terminal of the mixer MX1.

[0091] Dispersion imparted by the dispersion imparting filter DF4 is set to be of opposite sign to dispersion imparted by a dispersion imparting filter DF2. That is, in a case where the dispersion imparting filter DF2 imparts positive dispersion +D [s/Hz], the dispersion imparting filter DF4 imparts negative dispersion −D [s/Hz], and in a case where the dispersion imparting filter DF2 imparts negative dispersion −D [s/Hz], the dispersion imparting filter DF4 imparts positive dispersion +D [s/Hz].

[0092] Accordingly, a second radio frequency signal V.sub.RF′(t) having a more appropriate delay as compared with the time delay device 1 is outputted from an output terminal of a mixer MX2.

[0093] (Operation of Time Delay Device)

[0094] The following description will discuss an operation the time delay device 3 having the configuration above in which operation the first radio frequency signal V.sub.RF(t) and a first local signal V.sub.LO(t) are supplied to the time delay device 3 and eventually the second radio frequency signal V.sub.RF′(t) is outputted from the time delay device 3.

[0095] First, on the assumption that the dispersion imparting filter DF2 imparts positive dispersion +D [s/Hz] and the dispersion imparting filter DF4 imparts negative dispersion −D [s/Hz], the first radio frequency signal V.sub.RF(t) represented by the formula (15) is imparted a delay Df.sub.RF+θ.sub.0+θ.sub.5 by being transmitted through the dispersion imparting filter DF4. Accordingly, the second radio frequency signal V.sub.RF′(t) supplied to a second input terminal of the mixer MX1 is represented by the following formula (24).

[Math 24]

V.sub.RF′(t)=V.sub.RF cos(2πf.sub.RF(t−Df.sub.RF−θ.sub.0−θ.sub.5))  (24)

[0096] The mixer MX1 generates a first intermediate frequency signal V.sub.IF(t) represented by the following formula (25), by down-converting the second radio frequency signal V.sub.RF′(t) with use of a second local signal V.sub.LO′(t) as represented by the formula (17).

[00013]$\begin{array}{cc}.Math.\left[\mathrm{Math}.Math..Math.25\right]& \\ V_{\mathrm{IF}}\left(t\right)=\frac{v_{\mathrm{RF}}.Math.v_{\mathrm{LO}}}{2}.Math.\cos (.Math.2.Math.\pi \left(f_{\mathrm{RF}}-f_{\mathrm{LO}}\right).Math.t-2.Math.\pi .Math..Math.D.Math..Math.f_{\mathrm{RF}}^2+2.Math.\pi \left(f_{\mathrm{LO}}.Math.{\theta }_1-f_{\mathrm{RF}}.Math.{\theta }_0-f_{\mathrm{RF}}.Math.{\theta }_5\right))& \left(25\right)\end{array}$

[0097] The first intermediate frequency signal V.sub.IF(t) is imparted a delay as described above by a third transmission line TL3 and the dispersion imparting filter DF2 so as to become a second intermediate frequency signal V.sub.IF′(t) represented by the following formula (26), and then is supplied to a second input terminal of the mixer MX2.

[00014]$\begin{array}{cc}.Math.\left[\mathrm{Math}.Math..Math.26\right]& \\ V_{\mathrm{IF}}^{\prime }\left(t\right)=\frac{v_{\mathrm{RF}}.Math.v_{\mathrm{LO}}}{2}.Math.\cos \left(2.Math.\pi \left(f_{\mathrm{RF}}-f_{\mathrm{LO}}\right).Math.\left\{t+D\left(f_{\mathrm{RF}}-f_{\mathrm{LO}}\right)-{\theta }_0-{\theta }_3\right\}-2.Math.\pi .Math..Math.D.Math..Math.f_{\mathrm{RF}}^2+2.Math.\pi \left(f_{\mathrm{LO}}.Math.{\theta }_1-f_{\mathrm{RF}}.Math.{\theta }_0-f_{\mathrm{RF}}.Math.{\theta }_5\right)\right)& \left(26\right)\end{array}$

[0098] The mixer MX2 generates a second radio frequency signal V.sub.RF′(t) represented by the following formula (27), by up-converting the second intermediate frequency signal VIP′(t) with use of a third local signal V.sub.LO′(t) as represented by the formula (19).

[00015]$\begin{array}{cc}.Math.\left[\mathrm{Math}.Math..Math.27\right]& \\ V_{\mathrm{RF}}^{\prime }\left(t\right)=\frac{v_{\mathrm{RF}}.Math.v_{\mathrm{LO}}^2}{4}.Math.\cos \left(2.Math.\pi .Math..Math.f_{\mathrm{RF}}.Math.\left\{t-\left(\frac{{\theta }_1+{\theta }_2-{\theta }_2}{f_{\mathrm{RF}}}+2.Math.D\right).Math.f_{\mathrm{LO}}-2.Math.{\theta }_0-{\theta }_3-{\theta }_5\right\}\right)& \left(27\right)\end{array}$

[0099] It is known from the formula (27) that the Df.sub.RF term which is included in the delay δ, represented by the formula (22) or (23), in the time delay device 1 is absent in a delay included in the second radio frequency signal V.sub.RF′(t).

[0100] Thus, it is known from Embodiments 2 and 3 that a dispersion imparting filter which has a function of canceling the term Df.sub.RF from a delay δ can be inserted on a transmission line that supplies a first radio frequency signal V.sub.RF(t) to a mixer MX1 or can be inserted on a transmission line to which a second radio frequency signal V.sub.RF′(t) is outputted from a mixer MX2.

Embodiment 4

[0101] With reference to FIG. 4, the following description will discuss, as Embodiment 4, a transmitting phased array antenna 4 which includes the time delay device 1. FIG. 4 is a block diagram showing a configuration of the phased array antenna 4. For easy explanation, the same reference signs will be given to configurations each having the same function as a configuration described in Embodiments 1 through 3, and descriptions on such a configuration will be omitted.

[0102] The phased array antenna 4 is a transmitting antenna which includes n antenna elements A1, A2, . . . , An and n time delay devices TD11, TD12, . . . , TD1n, as shown in FIG. 4. To each time delay device TD1i (i=1 to n), a radio frequency signal V.sub.RF(t) (corresponding to the first radio frequency signal described above) outputted from a radio frequency signal source RF is supplied in common. A radio frequency signal V.sub.RF(t−δi) (corresponding to the second radio frequency signal described above) delayed by each time delay device TD1i is supplied to a corresponding antenna element Ai.

[0103] In the phased array antenna 4, a local signal V.sub.LOi(t) generated by each of local signal sources LO1, LO2, . . . , LOn has a frequency f.sub.LOi which is set in accordance with a position of a corresponding antenna element Ai in an order in which the antenna elements Ai are arranged, wherein the frequencies f.sub.LOi of the respective antenna elements Ai have an equal difference therebetween. Accordingly, delays δ1, δ2, . . . , δn which are imparted by the time delay devices TD11, TD12, . . . , TD1n to the first radio frequency signal V.sub.RF(t) are each set in accordance with a position of a corresponding antenna element Ai in an order in which the antenna elements Ai are arranged, wherein the delays δ1, δ2, . . . , δn have an equal difference therebetween. By setting a frequency difference Δf.sub.LO=f.sub.LO2−f.sub.LO1=f.sub.LO3−f.sub.LO2= . . . =f.sub.LOn−f.sub.LOn-1 so that a time delay difference Δt=δ2−δ1=δ3−δ2= . . . =δn−δn−1 coincides with d×sin α/c, it is possible to transmit efficiently an electromagnetic wave which has an equiphase plane with a tilt of α.

[0104] <<Comparison of Main Beam Direction According to the Present Invention and Main Beam Direction According to Conventional Technique>>

[0105] (Main Beam Direction According to the Present Invention)

[0106] First, on the basis of the formula (22), a delay δi of each time delay device TDi is represented by the following formula (28).

[00016]$\begin{array}{cc}\left[\mathrm{Math}.Math..Math.28\right]& \\ {\delta }_i=\left(\frac{{\theta }_2-\left({\theta }_1+{\theta }_3\right)}{f_{\mathrm{RF}}}+2.Math.D\right).Math.f_{\mathrm{LOi}}-{\mathrm{Df}}_{\mathrm{RF}}+{\theta }_0+{\theta }_3& \left(28\right)\end{array}$

[0107] Then, a time delay difference Δt=δi−δi−1 between each adjacent ones TD1i and TD1i−1 of the time delay devices is represented by the following formula (29).

[00017]$\begin{array}{cc}\left[\mathrm{Math}.Math..Math.29\right]& \\ \Delta .Math..Math.t={\delta }_i-{\delta }_{i-1}=\left(\frac{{\theta }_2-\left({\theta }_1+{\theta }_3\right)}{f_{\mathrm{RF}}}+2.Math.D\right).Math.\left(f_{\mathrm{LOi}}-f_{\mathrm{LOi}-1}\right)& \left(29\right)\end{array}$

[0108] In a case where frequencies of first local signals V.sub.LO(t) supplied to the respective adjacent time delay devices TD1i and TDi-1 are f.sub.LOi and f.sub.LOi-1 and a frequency difference (f.sub.LOi−f.sub.LOi-1) in the formula (29) is Δf.sub.LO, the time delay difference Δt is represented by the following formula (30).

[Math 30]

|Δt|=2D|Δf.sub.LO|  (30)

[0109] It is known from the formula (30) that, according to the transmitting phased array antenna 4 which includes the time delay device 1 in accordance with one aspect of the present invention, no matter how a frequency f.sub.RF of the first radio frequency signal V.sub.RF(t) changes, the time delay difference Δt is uniquely defined on the basis of (i) dispersion D imparted by each of the dispersion imparting filters DF1 and DF2 and (ii) the frequency difference Δf.sub.LO between the first local signals V.sub.LO(t). This applies also to transmitting phased array antennas which respectively include the time delay device 2 and the time delay device 3.

[0110] The following description will discuss specific examples of how a main beam direction is set. For example, in a case where an electromagnetic wave in 60 GHz band (not less than 57 GHz and not more than 66 GHz) is radiated, a distance between each adjacent ones of the antenna elements can, for example, be set to ½ of a free space wavelength corresponding to a center frequency of 61.5 GHz, that is, be set to 2.44 mm. Further, an electrical length of a second transmission line TL2 is set equal to a sum of an electrical length of a first transmission line TL1 and an electrical length of a third transmission line TL3, so that θ.sub.2−(θ.sub.1+θ.sub.3)=0. A magnitude D of dispersion imparted by each of the dispersion imparting filters DF1 and DF2 is set to 5.7 ps/GHz, and the frequency difference Δf.sub.LO is set to 0.5 GHz. In this case, when these values are substituted into the dispersion D and the frequency difference Δf.sub.LO, respectively, in the formula (30), the time delay difference Δt is 5.7 ps. On the basis of this value of the time delay difference Δt and d=2.44 mm, an angle α of a main beam direction determined from Δt=d sin α/c is approximately 45°.

[0111] Further, in a case where an electromagnetic wave in 70 GHz band (not less than 71 GHz and not more than 76 GHz) is radiated, a distance between each adjacent ones of the antenna elements can, for example, be set to ½ of a free space wavelength corresponding to a center frequency of 73.5 GHz, that is, be set to 2.04 mm. In this case, too, an angle α of a main beam direction is determined in exactly the same way as above, so that the angle α is approximately 45°.

[0112] (Main Beam Direction According to Conventional Technique)

[0113] It has been discussed above that a delay δ in the time delay device 20 which includes the configuration (FIG. 16) of Patent Literature 1 is obtained by the formula (6).

[0114] In a case where the frequency f.sub.RF is 57 GHz, a necessary frequency difference Δf.sub.LO between first local signals V.sub.LO(t) for each adjacent ones of the time delay devices is 3.2 GHz. Under this condition, a time delay difference Δt obtained on the basis of the formula (6) in a case where a delay θ.sub.1 imparted by the phase shifter PS is 100 ps and the frequency f.sub.RF is 66 GHz is approximately 4.9 ps. An angle α of a main beam direction corresponding to this time delay difference is approximately 37°.

[0115] Further, in a case where the frequency f.sub.RF is 71 GHz, a necessary frequency difference Δf.sub.LO between first local signals V.sub.LO(t) for each adjacent ones of the time delay devices is 3.4 GHz. Under this condition, a time delay difference Δt obtained on the basis of the formula (6) in a case where a delay θ.sub.1 imparted by the phase shifter PS is 100 ps and the frequency f.sub.RF is 76 GHz is approximately 4.5 ps. An angle α of a main beam direction corresponding to this time delay difference is approximately 41°.

[0116] As described above, according to the time delay device of Patent Literature 1, a change in frequency f.sub.RF undesirably causes a change in angle α of a main beam direction. It is therefore evident that the time delay device in accordance with the present invention is advantageous over the time delay device of Patent Literature 1.

Embodiment 5

[0117] With reference to FIG. 5, the following description will discuss, as Embodiment 5, a receiving phased array antenna 5 which includes the time delay device 1. FIG. 5 is a block diagram showing a configuration of the phased array antenna 5. For easy explanation, the same reference signs will be given to configurations each having the same function as a configuration described in Embodiments 1 through 4, and descriptions on such a configuration will be omitted.

[0118] The phased array antenna 5 is a receiving antenna which includes n antenna elements A1, A2, . . . , An and n time delay devices TD21, TD22, . . . , TD2n, as shown in FIG. 5. To each time delay device TD2i (i=1 to n), a radio frequency signal V.sub.RF(t+δi) (corresponding to the first radio frequency signal described above) outputted from a corresponding antenna element Ai is supplied individually. Radio frequency signals V.sub.RF(t) (each corresponding to the second radio frequency signal described above) delayed by the respective time delay devices TD2i are combined and then outputted outside the phased array antenna 5.

[0119] In the phased array antenna 5, a first local signal V.sub.LO(t) generated by each of local signal sources LO1, LO2, . . . , LOn has a frequency f.sub.LO which is set in accordance with a position of a corresponding antenna element Ai in an order in which the antenna elements Ai are arranged, wherein the frequencies f.sub.LO of the respective antenna elements Ai have an equal difference therebetween. Accordingly, delays δ1, δ2, . . . , δn which are imparted by the time delay devices TD21, TD22, . . . , TD2n to the radio frequency signal V.sub.RF(t) are each set in accordance with a position of a corresponding antenna element Ai in an order in which the antenna elements Ai are arranged, wherein the delays δ1, δ2, . . . , δn have an equal difference therebetween. By setting a frequency difference Δf.sub.LO=f.sub.LO2−f.sub.LO1=f.sub.LO3−f.sub.LO2= . . . =f.sub.LOn−f.sub.LOn-1 so that a time delay difference Δt=δ2−δ1=δ3−δ2= . . . =δn−δn−1 coincides with d×sin α/c, it is possible to receive efficiently an electromagnetic wave which has an equiphase plane with a tilt angle of α.

Embodiment 6

[0120] With reference to FIG. 6, the following description will discuss, as Embodiment 6, a transmitting and receiving phased array antenna 6 which includes the time delay device 1. FIG. 6 is a block diagram showing a configuration of the phased array antenna 6. For easy explanation, the same reference signs will be given to configurations each having the same function as a configuration described in Embodiments 1 through 5, and descriptions on such a configuration will be omitted.

[0121] As shown in FIG. 6, the phased array antenna 6 is a transmitting and receiving phased array antenna which is obtained by combining the transmitting phased array antenna 4 shown in FIG. 4 and the receiving phased array antenna 5 shown in FIG. 5.

[0122] Note that the phased array antenna 6 has only one (1) set of local signal sources LO1 through LOn, which are shared by the phased array antenna 4 and the phased array antenna 5. More specifically, each local signal source LOi is connected to both of a corresponding time delay device TD1i in the phased array antenna 4 and a corresponding time delay device TD2i in the phased array antenna 5. Further, the phased array antenna 6 has only one (1) set of antenna elements A1 through An, which are shared by the phased array antenna 4 and the phased array antenna 5. More specifically, each antenna element Ai is connected to both of a corresponding time delay device TD1i in the phased array antenna 4 and a corresponding time delay device TD2i in the phased array antenna 5.

Embodiment 7

[0123] With reference to FIG. 7, the following description will discuss, as Embodiment 7, another transmitting phased array antenna 7 which includes the time delay device 1. FIG. 7 is a block diagram showing a configuration of the phased array antenna 7. For easy explanation, the same reference signs will be given to configurations each having the same function as a configuration described in Embodiments 1 through 6, and descriptions on such a configuration will be omitted.

[0124] The phased array antenna 7 is a transmitting antenna which includes n antenna elements A1, A2, . . . , An and n time delay devices TD11, TD12, . . . , TD1n, as shown in FIG. 7. To each time delay device TD1i (i=1 to n), a radio frequency signal V.sub.RF(t) (corresponding to the first radio frequency signal described above) outputted from a radio frequency signal source RF is supplied in common. A radio frequency signal V.sub.RF(t−δi) delayed by each time delay device TD1i is supplied to a corresponding antenna element Ai.

[0125] A characteristic point of the phased array antenna 7 is that the phased array antenna 7 includes only one (1) local signal source LO and only one (1) mixer MX1, each of which is shared by the n time delay devices TD11, TD12, . . . , TD1n.

[0126] The shared mixer MX1 has (i) a first input terminal which is connected to an output terminal of the radio frequency signal source RF which is shared by the n time delay devices TD11, TD12, . . . , TD1n, and (ii) a second input terminal which is connected, via a first transmission line TL1 which is shared by the n time delay devices TD11, TD12, . . . , TD1n, to an output terminal of the shared local signal source LO. Accordingly, the shared mixer MX1 is supplied with (i) the radio frequency signal V.sub.RF(t) generated by the shared radio frequency signal source RF and (ii) a second local signal V.sub.LO′(t) obtained by delaying, by the shared first transmission line TL1, a first local signal V.sub.LO(t) generated by the shared local signal source LO. The shared mixer MX1 generates an intermediate frequency signal V.sub.IF(t) by down-converting the first radio frequency signal V.sub.RF(t) with use of the second local signal V.sub.LO′(t).

[0127] A mixer MX2 of each time delay device TD1i has (i) a first input terminal which is connected to the output terminal of the shared local signal source LO via a second transmission line TL2 (including a dispersion imparting filter DF1) of the each time delay device TD1i and (ii) a second input terminal which is connected to an output terminal of the shared mixer MX1 via a third transmission line TL3 (including a dispersion imparting filter DF2) of the each time delay device TD1i. Accordingly, the mixer MX2 of each time delay device TD1i is supplied with (i) a third local signal V.sub.LO′(t) obtained by delaying, by the second transmission line TL2 of the each time delay device TD1i, the first local signal V.sub.LO(t) generated by the shared local signal source LO and (ii) a second intermediate frequency signal V.sub.IF′(t) obtained by delaying, by the third transmission line TL3 of the each time delay device TD1i, the intermediate frequency signal V.sub.IF(t) generated by the shared mixer MX1. The mixer MX2 of each time delay device TD1i generates a second radio frequency signal V.sub.RF′(t) by up-converting the second intermediate frequency signal V.sub.IF′(t) with use of the third local signal V.sub.LO″(t). The second radio frequency signal V.sub.RF′(t) generated by the mixer MX2 of each time delay device TD1i is supplied to an antenna element Ai corresponding to the time delay device TD1i. Note that an electrical length of a second transmission line TL2 and an electrical length of a third transmission line TL3 are each equal between the time delay elements TD11 through TD1n.

[0128] Note that it is possible to employ a configuration in which, on a transmission line through which the second radio frequency signal V.sub.RF′(t) outputted from each mixer MX2 is transmitted to a corresponding antenna element Ai, a dispersion imparting filter DF3 (a third dispersion imparting filter) that imparts dispersion of opposite sign to dispersion imparted by the dispersion imparting filter DF2 is inserted. More specifically, a circulator C3 is inserted between each mixer MX2 and a corresponding antenna element Ai, and a first port, a second port, and a third port of the circulator C3 are respectively connected to an output terminal of the each mixer MX2, the dispersion imparting filter DF3, and the antenna element Ai.

[0129] This allows eliminating, from a delay Si of the second radio frequency signal V.sub.RF′(t) outputted from each time delay device TD1i with respect to the first radio frequency signal V.sub.RF(t), a term +Df.sub.RF or −Df.sub.RF which is in proportion to a frequency f.sub.RF of the first radio frequency signal V.sub.RF(t). As a result, it is possible to suppress disruption of a signal waveform of the second radio frequency signal V.sub.RF′(t) caused by the transmission line through which the second radio frequency signal V.sub.RF′(t) is transmitted to the antenna element Ai. This enables an improvement in signal quality of the second radio frequency signal V.sub.RF′(t).

[0130] In the phased array antenna 7, dispersion imparted by each of the dispersion imparting filters DF1 and DF2 of each of the time delay devices TD11, TD12, . . . , TD1n is set in accordance with a position of a corresponding antenna element Ai in an order in which the antenna elements Ai are arranged, wherein dispersion imparted in the respective time delay devices TD11, TD12, . . . , TD1n have an equal difference therebetween. That is, dispersion imparted by the respective dispersion imparting filters DF1 of the time delay devices TD11, TD12, . . . , TD1n are set to -D, −(D+ΔD), . . . , −(D+(n−1)ΔD), respectively, and dispersion imparted by the respective dispersion imparting filters DF2 of the time delay devices TD11, TD12, . . . , TD1n are set to D, D+ΔD, . . . , D+(n−1)ΔD, respectively. Accordingly, delays δ1, δ2, . . . , δn which are imparted by the time delay devices TD11, TD12, . . . , TD1n to the radio frequency signal V.sub.RF(t) are each set in accordance with a position of a corresponding antenna element Ai in an order in which the antenna elements Ai are arranged, wherein the delays δ1, δ2, . . . , δn have an equal difference therebetween. By setting a dispersion difference ΔD so that a time delay difference Δt=δ2−δ1=δ3−δ2= . . . =δn−δn−1 coincides with d×sin α/c, it is possible to transmit efficiently an electromagnetic wave which has an equiphase plane with a tilt angle of α.

[0131] In the phased array antenna 7, the time delay difference Δt is, as shown by the following formula (31), in proportion to a frequency f.sub.LO of the first local signal V.sub.LO(t), wherein a proportionality coefficient does not depend on the frequency f.sub.RF of the radio frequency signal V.sub.RF(t). As such, according to the phased array antenna 7, it is possible to perform, over a wide band, accurate control of a direction (a main beam direction of an electromagnetic wave radiated) in which an electromagnetic wave can be efficiently transmitted.

[Math 31]

Δt=2d Δf.sub.LO  (31)

Embodiment 8

[0132] With reference to FIG. 8, the following description will discuss, as Embodiment 8, a receiving phased array antenna 8 which includes a modified example of the time delay device 1. FIG. 8 is a block diagram showing a configuration of the phased array antenna 8.

[0133] The phased array antenna 8 is a receiving antenna which includes n antenna elements A1, A2, . . . , An and n time delay devices TD21, TD22, . . . , TD2n, as shown in FIG. 8. To each time delay device TD2i (i=1 to n), a radio frequency signal V.sub.RP(t+δi) (corresponding to the first radio frequency signal described above) outputted from a corresponding antenna element Ai is supplied individually. Radio frequency signals V.sub.RF(t) (corresponding to the second radio frequency signal described abovej delayed by the respective time delay devices TD2i are combined and then outputted outside the phased array antenna 8.

[0134] A characteristic point of the phased array antenna 8 is that the phased array antenna 8 includes only one (1) local signal source LO, which is shared by the n time delay devices TD21, TD22, . . . , TD2n.

[0135] A mixer MX1 of each time delay device TD2i has (i) a first input terminal which is connected to a corresponding antenna element Ai and (ii) a second input terminal which is connected, via a first transmission line TL1 of the each time delay device TD2i, to an output terminal of the shared local signal source LO. Accordingly, the mixer MX1 of each time delay device TD2i is supplied with (i) the radio frequency signal V.sub.RF(t) outputted from the corresponding antenna element Ai and (ii) a second local signal V.sub.LO′(t) obtained by delaying, by the first transmission line TL1 of the each time delay device TD2i, the first local signal V.sub.LO(t) generated by the shared local signal source LO. The shared mixer MX1 of each time delay device TD2i generates an intermediate frequency signal V.sub.IF(t) by down-converting the first radio frequency signal V.sub.RF(t) with use of the second local signal V.sub.LO′(t).

[0136] A mixer MX2 of each time delay device TD2i has (i) a first input terminal which is connected to the output terminal of the shared local signal source LO via a second transmission line TL2 (including a dispersion imparting filter DF1) of the each time delay device TD2i and (ii) a second input terminal which is connected to an output terminal of the mixer MX1 of the each time delay device TD2i via a third transmission line TL3 (including a dispersion imparting filter DF2) of the each time delay device TD2i. Accordingly, the mixer MX2 of each time delay device TD2i is supplied with (i) a third local signal V.sub.LO′(t) obtained by delaying, by the second transmission line TL2 of the each time delay device TD2i, the first local signal V.sub.LO(t) generated by the shared local signal source LO and (ii) a second intermediate frequency signal V.sub.IF′(t) obtained by delaying, by the third transmission line TL3 of each time delay device TD2i, the intermediate frequency signal V.sub.IF(t) generated by the mixer MX1 of each time delay device TD2i. The mixer MX2 of each time delay device TD2i generates a second radio frequency signal V.sub.RF′(t) by up-converting the second intermediate frequency signal V.sub.IF′(t) with use of the third local signal V.sub.LO″(t). The second radio frequency signals V.sub.RF′(t) generated by the respective mixers MX2 of the time delay devices TD2i are combined and then outputted outside the phased array antenna 8. Note that an electrical length of a first transmission line TL1, an electrical length of a second transmission line TL2, and an electrical length of a third transmission line TL3 are each equal between the time delay elements TD21 through TD2n.

[0137] Note that it is possible to employ a configuration in which, on a transmission line to which the second radio frequency signal V.sub.RF′(t) is outputted from each mixer MX2, a dispersion imparting filter DF3 (a third dispersion imparting filter) that imparts dispersion of opposite sign to dispersion imparted by the dispersion imparting filter DF2 is inserted. More specifically, a circulator C3 is inserted between each mixer MX2 and a combining terminal which outputs a sum signal between the second radio frequency signals V.sub.RF′(t) outputted by the respective time delay devices TD2i, and a first port, a second port, and a third port of the circulator C3 are respectively connected to an output terminal of the each mixer MX2, the dispersion imparting filter DF3, and the combining terminal.

[0138] This allows eliminating, from a delay Si of the second radio frequency signal V.sub.RF′(t) outputted from each time delay device TD2i with respect to the first radio frequency signal V.sub.RF(t), a term +Df.sub.RF or −Df.sub.RF which is in proportion to a frequency f.sub.RF of the first radio frequency signal V.sub.RF(t). As a result, it is possible to suppress disruption of a signal waveform of the second radio frequency signal V.sub.RF′(t) caused by the transmitted transmission line to which the second radio frequency signal V.sub.RF′(t) is outputted. This enables an improvement in signal quality of the second radio frequency signal V.sub.RF′(t).

[0139] Note that, instead of providing the dispersion imparting filter DF3 on the transmission line for the second radio frequency signal V.sub.RF′(t) outputted from each time delay device TD2i, it is possible to employ a configuration in which, on a transmission line from which the first radio frequency signal V.sub.RF(t) is supplied to each time delay device TD2i, a dispersion imparting filter DF4 that imparts dispersion of opposite sign to dispersion imparted by the dispersion imparting filter DF2 is inserted as the third dispersion imparting filter. More specifically, a circulator C4 is inserted between each antenna element Ai and a corresponding time delay device TD2i, and a first port, a second port, and a third port of the circulator C4 are respectively connected to the each antenna element Ai, the dispersion imparting filter DF4, and the first input terminal of the mixer MX1 of the each time delay device TD2i. The addition of the dispersion imparting filter DF4 provides an effect identical to the previously discussed advantageous effect that is provided by the dispersion imparting filter DF3.

[0140] In the phased array antenna 8, dispersion imparted by each of the dispersion imparting filters DF1 and DF2 of each of the time delay devices TD21, TD22, . . . , TD2n is set in accordance with a position of a corresponding antenna element Ai in an order in which the antenna elements Ai are arranged, wherein dispersion imparted in the respective time delay devices TD21, TD22, . . . , TD2n have an equal difference therebetween. That is, dispersion imparted by the respective dispersion imparting filters DF1 of the time delay devices TD21, TD22, . . . , TD2n are set to −D, −(D+ΔD), . . . , −(D+(n−1)ΔD), respectively, and dispersion imparted by the respective dispersion imparting filters DF2 of the time delay devices TD21, TD22, . . . , TD2n are set to D, D+ΔD, . . . , D+(n−1)ΔD, respectively. Accordingly, delays δ1, δ2, . . . , δn which are imparted by the time delay devices TD21, TD22, . . . , TD2n to the radio frequency signal V.sub.RF(t) are each set in accordance with a position of a corresponding antenna element Ai in an order in which the antenna elements Ai are arranged, wherein the delays δ1, δ2, . . . , δn have an equal difference therebetween. By setting a dispersion difference ΔD so that a time delay difference Δt=δ2−δ1=δ3−δ2= . . . =δn−δn−1 coincides with d×sin α/c, it is possible to receive efficiently an electromagnetic wave which has an equiphase plane with a tilt angle of α.

Embodiment 91

[0141] As Embodiment 9, the following description will discuss a transmitting and receiving phased array antenna 9 with reference to FIG. 9. FIG. 9 is a block diagram showing a configuration of the phased array antenna 9.

[0142] As shown in FIG. 9, the phased array antenna 9 is a transmitting and receiving phased array antenna which is obtained by combining the transmitting phased array antenna 4 shown in FIG. 4 and the receiving phased array antenna 8 shown in FIG. 8.

[0143] The phased array antenna 9 thus configured also provides effects identical to the previously discussed effects provided by the transmitting and receiving phased array antenna 6.

Embodiment 10

[0144] As Embodiment 10, the following description will discuss a transmitting and receiving phased array antenna 10 with reference to FIG. 10. FIG. 10 is a block diagram showing a configuration of the phased array antenna 10.

[0145] As shown in FIG. 10, the phased array antenna 10 is a transmitting and receiving phased array antenna which is obtained by combining the transmitting phased array antenna 7 shown in FIG. 7 and the receiving phased array antenna 5 shown in FIG. 5.

[0146] The phased array antenna 10 thus configured also provides effects identical to the previously discussed effects provided by the transmitting and receiving phased array antenna 6.

Embodiment 11

[0147] As Embodiment 11, the following description will discuss a transmitting and receiving phased array antenna 11 with reference to FIG. 11. FIG. 11 is a block diagram showing a configuration of the phased array antenna 11.

[0148] As shown in FIG. 11, the phased array antenna 11 is a transmitting and receiving phased array antenna which is obtained by combining the transmitting phased array antenna 7 shown in FIG. 7 and the receiving phased array antenna 8 shown in FIG. 8.

[0149] The phased array antenna 11 thus configured also provides effects identical to the previously discussed effects provided by the transmitting and receiving phased array antenna 6.

CONCLUSION

[0150] In order to attain the object, a time delay device in accordance with one aspect of the present invention is a time delay device including: a first transmission line which generates a second local signal V.sub.LO′(t)=V.sub.LO(t−θ.sub.1) by imparting a delay θ.sub.1 to a first local signal V.sub.LO(t) having a frequency f.sub.LO; a first mixer which generates a first intermediate frequency signal V.sub.IF(t) having a frequency f.sub.RF−f.sub.LO, by multiplying a first radio frequency signal V.sub.RF(t) having a frequency f.sub.RF (f.sub.LO<f.sub.RF) by the second local signal V.sub.LO′(t); a second transmission line on which a first dispersion imparting filter is inserted, the second transmission line generating a third local signal V.sub.LO″(t)=V.sub.LO(t−θ.sub.D−θ.sub.2) by imparting, to the first local signal V.sub.LO(t), a delay θ.sub.D by the first dispersion imparting filter and a delay θ.sub.2 by the second transmission line; a third transmission line on which a second dispersion imparting filter is inserted, the second dispersion imparting filter imparting dispersion of opposite sign to dispersion imparted by the first dispersion imparting filter, the third transmission line generating a second intermediate frequency signal V.sub.IF′(t)=V.sub.IF(t−θ.sub.D′−θ.sub.3) by imparting, to the first intermediate frequency signal V.sub.IF(t), a delay θ.sub.D′ by the second dispersion imparting filter and a delay θ.sub.3 by the third transmission line; and a second mixer which generates a second radio frequency signal V.sub.RF′(t) having the frequency f.sub.RF, by multiplying the third local signal V.sub.LO″(t) by the second intermediate frequency signal V.sub.IF′(t).

[0151] According to the arrangement above, in a case where the delay θ.sub.D imparted by the first dispersion imparting filter is represented as θ.sub.D′=+Df.sub.LO+θ.sub.0, and the delay θ.sub.D′ imparted by the second dispersion imparting filter is represented as θ.sub.D′=−D(f.sub.RF−f.sub.LO)+θ.sub.0, a delay δ of the second radio frequency signal V.sub.RF′(t) with respect of the first radio frequency signal V.sub.RF(t) can be δ={(θ.sub.2−θ.sub.1−θ.sub.3)/f.sub.RF+2D}f.sub.LO−Df.sub.RF+θ.sub.0+θ.sub.3 or δ={(θ.sub.2−θ.sub.1−θ.sub.3)/f.sub.RF−2D}f.sub.LO+Df.sub.RF+θ.sub.0+θ.sub.3. Accordingly, it is possible to change the delay δ in accordance with the frequency f.sub.LO of the first local signal V.sub.LO(t).

[0152] Further, according to the arrangement above, an amount of change Δf.sub.LO in frequency f.sub.LO, which is a control variable, of the local signal V.sub.LO(t) and an amount of change Δδ in delay δ, which is a controlled variable, are in a relation: Δδ={(θ.sub.2−θ.sub.1−θ.sub.3)/f.sub.RF+2D}Δf.sub.LO or a relation: Δδ={(θ.sub.2−θ.sub.1−θ.sub.3)/f.sub.RF-2D}Δf.sub.LO. Accordingly, for example, as an electrical length of the second transmission line is approximated to a sum of an electrical length of the first transmission line and an electrical length of the third transmission line so that θ.sub.2−θ.sub.1−θ.sub.3 is approximated to 0, a degree of dependency of the amount of change Δδ in delay δ on the frequency f.sub.RF of the radio frequency signal V.sub.RF(t) can be reduced to whatever extent. This allows control of the delay δ imparted to the first radio frequency signal V.sub.RF(t) to be performed more accurately over a wide band, as compared with a conventional technique.

[0153] The time delay device in accordance with one aspect of the present invention is preferably configured such that the second transmission line has an electrical length equal to a sum of an electrical length of the first transmission line and an electrical length of the third transmission line.

[0154] According to the arrangement above, θ.sub.2−θ.sub.1−θ.sub.3=0. As such, the amount of change Δf.sub.LO in frequency f.sub.LO, which is a control variable, of the local signal V.sub.LO(t) and the amount of change Δδ in delay δ, which is a controlled variable, are in a relation: Δδ=2DΔf.sub.LO or a relation: Δδ=−2DΔf.sub.LO. Accordingly, the amount of change Δδ in delay δ does not depend on the frequency f.sub.RF of the radio frequency signal V.sub.RF(t). This allows control of the delay δ imparted to the first radio frequency signal V.sub.RF(t) to be performed even more accurately over a wide band.

[0155] The time delay device in accordance with one aspect of the present invention may be configured such that each of the first dispersion imparting filter and the second dispersion imparting filter is constituted by a CEBG (Chirped Electromagnetic Bandgap) transmission line.

[0156] The CEBG transmission line is a microstrip line which is capable of imparting dispersion to an input signal (imparting a delay that is in proportion to a frequency of the input signal). As such, according to the arrangement above, it is possible to provide each of the first dispersion imparting filter and the second dispersion imparting filter at low cost (at a cost similar to that of the microstrip line).

[0157] The time delay device in accordance with one aspect of the present invention is preferably configured such that a third dispersion imparting filter which imparts dispersion of opposite sign to the dispersion imparted by the second dispersion imparting filter is inserted on (i) a transmission line that transmits the first radio frequency signal V.sub.RF(t) supplied to the first mixer or (ii) a transmission line that transmits the second radio frequency signal V.sub.RF′(t) outputted from the second mixer.

[0158] According to the arrangement above, it is possible to eliminate, from the delay δ of the second radio frequency signal V.sub.RF′(t) with respect to the first radio frequency signal V.sub.RF(t), a term +Df.sub.RF or −Df.sub.RF which is in proportion to the frequency f.sub.RF of the radio frequency signal V.sub.RF(t).

[0159] A phased array antenna in accordance with a first aspect of the present invention is a phased array antenna including: n (n is an integer of 2 or more) antenna elements A1 through An; and n time delay devices TD11 through TD1n, each time delay device TD1i (i=1 to n) having any of the configurations of the time delay device above, the second radio frequency signal generated by the each time delay device TD1i being supplied to a corresponding antenna element Ai.

[0160] According to the arrangement above, it is possible to provide a transmitting phased array antenna which allows control of a direction (a main beam direction of an electromagnetic wave transmitted) in which an electromagnetic wave can be efficiently transmitted to be performed more accurately over a wide band as compared with a conventional technique.

[0161] The phased array antenna in accordance with one aspect of the present invention is preferably arranged such that the first local signal supplied to the each time delay device TD1i has a frequency which is set in accordance with a position of the corresponding antenna element Ai in an order in which the respective antenna elements Ai are provided, the frequencies of the respective time delay devices TD1i having an equal difference therebetween.

[0162] According to the arrangement above, in a case where the antenna elements A1 through An are arranged on the same straight line at equal intervals, control of a direction (a main beam direction of an electromagnetic wave transmitted) in which an electromagnetic wave can be efficiently transmitted can be performed accurately over a wide band.

[0163] A phased array antenna in accordance with a second aspect of the present invention is a phased array antenna including: n (n is an integer of 2 or more) antenna elements A1 through An; and n time delay devices TD21 through TD2n, each time delay device TD2i (i=1 to n) having any of the configurations of the time delay device above, a radio signal outputted from each antenna element Ai being supplied, as the first radio frequency signal, to a corresponding time delay device TD2i.

[0164] According to the arrangement above, it is possible to provide a receiving phased array antenna which allows control of a direction in which an electromagnetic wave can be efficiently received to be performed more accurately over a wide band as compared with a conventional technique.

[0165] The phased array antenna in accordance with the second aspect of the present invention is preferably configured such that the first local signal supplied to the each time delay device TD2i has a frequency which is set in accordance with a position of a corresponding antenna element Ai in an order in which the respective antenna elements Ai are provided, the frequencies of the respective time delay devices TD2i having an equal difference therebetween.

[0166] According to the arrangement above, in a case where the antenna elements A1 through An are arranged on the same straight line at equal intervals, it is possible to perform control of a direction in which an electromagnetic wave can be efficiently received, accurately over a wide band.

[0167] A phased array antenna in accordance with a third aspect of the present invention is a phased array antenna including: the phased array antenna in accordance with the first aspect, the phased array antenna serving as a transmitting antenna; and the phased array antenna in accordance with the second aspect, the phased array antenna serving as a receiving antenna, the antenna elements A1 through An being shared by the transmitting antenna and the receiving antenna.

[0168] According to the arrangement above, it is possible to provide a transmitting and receiving phased array antenna which allows control of a direction in which an electromagnetic wave can be efficiently transmitted and received to be performed more accurately over a wide band as compared with a conventional technique.

[0169] [Additional Matter]

[0170] The present invention is not limited to the above-described embodiments and modified examples but allows various modifications within the scope of the claims. Any embodiment derived from an appropriate combination of the technical means disclosed in the embodiments or the modified examples will also be included in the technical scope of the present invention.

REFERENCE SIGNS LIST

[0171] 1, 2, 3 Time delay device [0172] 4, 5, 6, 7, 8, 9, 10, 11 Phased array antenna [0173] A1, A2, . . . , An Antenna element [0174] DF1 Dispersion imparting [0175] filter (first dispersion imparting filter) [0176] DF2 Dispersion imparting [0177] filter (second dispersion imparting filter) [0178] DF3, DF4 Dispersion imparting [0179] filter (third dispersion imparting filter) [0180] TD11, TD12, . . . , TD1n Time delay device [0181] TD21, TD22, . . . , TD2n Time delay device [0182] MX1 Mixer (first mixer) [0183] MX2 Mixer (second mixer) [0184] TL1 First transmission line [0185] TL2 Second transmission [0186] line [0187] TL3 Third transmission line