Switchless combiner for addressing of radiofrequency signals and system for transmission of radiofrequency signals comprising said combiner

Abstract

A switchless combiner includes a circuit having a delay line consisting of a constant-impedance transmission line and a device adapted to vary the electric length of said transmission line, the device including a metallic body with walls defining a cavity, the walls being interrupted to define a slot, the cavity and the slot extending along at least a portion of the length of the device, the cavity including a first portion having a first cross-section and a second portion having a second cross-section which is greater than the first cross-section, the second portion having a dielectric element with a cutout corresponding to the slot, the first and second portions extending in the longitudinal direction of the device and the transmission line being positioned, inside the first and second portion, in the cutout, the dielectric element occupying the cavity of the second portion, and having an element to translate the dielectric element on the circuit in the longitudinal direction of the device.

Claims

1. A switchless combiner comprising: a circuit having a delay line that includes a constant-impedance transmission line having a fixed length; and a device adapted to vary an electric length of said transmission line, wherein said device comprises a metallic body with an outer wall and an inner wall adapted to define a cavity, said walls being interrupted in a manner such as to define a slot, said cavity and said slot extending along at least a portion of a length of said device, wherein said cavity comprises a first portion having a first cross-section and a second portion having a second cross-section whose area is greater than an area of said first cross-section, said second portion comprising a dielectric element with a cutout corresponding to said slot, said first and second portions extending in the longitudinal direction of said device and said transmission line being positioned, inside said first portion and inside said second portion, in said cutout of said dielectric element, said dielectric element being adapted to occupy the cavity of said second portion, said metallic body being cylindrical, and said first and second cross-sections being circular; translating means integral with said metallic body for translating said dielectric element on said circuit in the longitudinal direction of said device; and a casing adapted to shield said device from the environment outside said casing.

2. The switchless combiner according to claim 1, wherein said dielectric element is made of a material having a relative dielectric constant greater than 1.

3. The switchless combiner according to claim 2, wherein said material is PTFE or a fiberglass-based material.

4. The switchless combiner according to claim 1, wherein said first portion of the cavity comprises a second dielectric element with a cutout corresponding to said slot, said second dielectric element being adapted to occupy the cavity of said first portion, and said second dielectric element having a different dielectric constant than a dielectric constant of said dielectric element.

5. The switchless combiner according to claim 1, wherein said delay line is positioned in said cavity.

6. The switchless combiner according to claim 5, wherein said transmission line is positioned centrally in said cavity, so that its edges are equidistant from said inner wall.

7. A transmitter comprising a switchless combiner according to claim 1.

8. A system of transmitters of signals comprising a first transmitter and a second transmitter associated with, respectively, a first transmission line and a second transmission line, a switchless combiner according to claim 1, wherein said switchless combiner is connected to said first and second transmitters and is adapted to introduce a delay on one or both signals transmitted on said first and second transmission lines.

9. The system according to claim 8, wherein said switchless combiner is configured to modify the phase delay on one or both of the first transmission line and the second transmission line, so as to suitably modulate a power of said signals being outputted by said switchless combiner.

10. A method for introducing a phase delay on a signal in transit in a switchless combiner comprising a circuit having a delay line that includes a constant-impedance transmission line and a device adapted to vary the electric length of said transmission line, said method comprising the steps of: positioning said transmission line into a cavity of the device, wherein the device includes a metallic body with an outer wall and an inner wall adapted to define said cavity, said walls being interrupted in a manner such as to define a slot, said cavity and said slot extending along at least a portion of the length of said device, wherein said cavity comprises a first portion having a first cross-section and a second portion having a second cross-section whose area is greater than an area of said first cross-section, said second portion comprising a dielectric element with a cutout corresponding to said slot, said first and second portions extending in the longitudinal direction of said device and said transmission line being positioned, inside said first portion and inside said second portion, in said cutout of said dielectric element, said dielectric element being adapted to occupy the cavity of said second portion, said device including a casing adapted to shield said device from an environment outside said casing, said metallic body being cylindrical, and said first and second cross-sections being circular; and translating said device on said circuit in the direction of its length through means for translating integral with said metallic body, so as to obtain a desired operating frequency.

11. The method according to claim 10, wherein said transmission line is positioned centrally in said cavity, so that its edges are equidistant from said inner wall.

12. A switchless combiner comprising: a circuit having a delay line that includes a constant-impedance transmission line having a fixed length; and a device adapted to vary an electric length of said transmission line, wherein said device comprises a metallic body with an outer wall and an inner wall adapted to define a cavity, said walls being interrupted in a manner such as to define a slot, said cavity and said slot extending along at least a portion of a length of said device, wherein said cavity comprises a first portion having a first cross-section and a second portion having a second cross-section whose area is greater than an area of said first cross-section, said second portion comprising a dielectric element with a cutout corresponding to said slot, said first and second portions extending in the longitudinal direction of said device and said transmission line being positioned, inside said first portion and inside said second portion, in said cutout of said dielectric element, said dielectric element being adapted to occupy the cavity of said second portion; translating means integral with said metallic body for translating said dielectric element on said circuit in the longitudinal direction of said device; wherein said metallic body is cylindrical, and said first and second cross-sections are circular.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above objects will become more apparent from the following detailed description of a switchless combiner comprising a device adapted to introduce a phase delay on the electric signals in transit therein, and a method thereof, with particular reference to the annexed drawings, wherein:

(2) FIG. 1 is a diagram of a prior-art transmission system;

(3) FIG. 2 is a longitudinal sectional view of a device for varying the electric length of a signal transmission line;

(4) FIGS. 2a and 2b are sectional views along the lines 2A-2A and 2B-2B, respectively, of FIG. 2;

(5) FIG. 3 shows various modes of operation of the switchless combiner according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(6) With reference to FIGS. 2, 2a and 2b, there is shown a device 10 for introducing a phase delay on a signal. Said phase delay is obtained by varying the electric length of a constant-impedance transmission line 12,12, in particular a transmission line having substantially constant thickness and width, adapted to transport an electric signal such as those inputted to a switchless combiner.

(7) The device 10 comprises a metallic body 14, e.g., made of aluminium or steel, extending in a substantially longitudinal direction D.

(8) The device 10 may comprise a casing 13, the function of which is to shield the device 10 from the environment outside the casing 13.

(9) The metallic body 14 has an outer wall 16, preferably with a constant cross-section, and an inner wall 22,22 that defines a cavity 20.

(10) The outer wall 16 and the inner wall 22,22 are interrupted in a manner such as to define a slot 24. The cavity 20 and the slot 24 extend along at least a portion of the length of the device 10.

(11) The cavity 20 comprises a first portion 21 having a first cross-section and a second portion 23 having a second cross-section, which is greater than the first cross-section.

(12) The second portion 23 of the cavity 20 comprises a dielectric element 27 with a cutout 25 which is positioned in correspondence of the slot 24 of the metallic body 14.

(13) The dielectric element 27 occupies the second portion 23 of the cavity 20 and is made of a dielectric material, e.g., teflon, also called PTFE (PolyTetraFluoroEthylene), having a greater dielectric constant than air.

(14) In a preferred embodiment of the invention, to which the following example will refer, the metallic body 14 is a parallelepipedon, and the first and second cross-sections of the cavity 20 are rectangular or square.

(15) As an alternative, the metallic body 14 is cylindrical, and the first and second cross-sections of the cavity 20 are circular.

(16) The device 10 further comprises translating means 11 integral with the metallic body 14, which allow the metallic body 14 to be translated along the longitudinal direction D.

(17) The translating means 11 may, for example, be moved manually or by means of a pinion/worm screw motor reducer system or a step motor (neither of which are shown) or other drive systems, whether electric or pneumatic.

(18) The translating means 11 can therefore be controlled from the outside of the metallic body 14 to act, through a suitable mechanical connection, upon the dielectric element 27 in such a way as to translate the dielectric element 27 itself, integrally with the metallic body 14, in the longitudinal direction D.

(19) The following will illustrate a method according to the invention for varying the electric length of a constant-impedance transmission line 12.

(20) With reference to FIG. 2a, it is assumed that the transmission line 12 has a section of thickness w and that a first edge 26 thereof is at a first distance z from the inner wall 22 of the metallic body 14 and a second edge 28 thereof is at a second distance y from the inner wall 22 of the metallic body 14: in this case, the first section d of the first portion 21 of the cavity 20 will be d=z+w+y.

(21) If the first distance z equals the second distance y, then the impedance along the transmission line 12 will remain constant.

(22) It must be pointed out that the impedance remains constant during the parallel motion of the metallic body 14 with respect to the transmission line 12.

(23) For example, assuming that the dielectric medium is air, that the thickness w of the transmission line 12 is 1 mm, and that the width of the transmission line 12 is approx. 7.5 mm, in order to obtain an impedance of 50? the first distance z and the second distance y will have to be set to 3 mm. The first portion 21 of the cavity 20 will therefore act as an air gap around the transmission line 12 immersed in a first dielectric medium, in particular air.

(24) Similar considerations apply to the second portion 23 of the cavity 20.

(25) With reference to FIG. 2b, in order to keep the impedance of the conductive element of the transmission line 12 constant, it is sufficient, in fact, to impose that the distance z of the first edge 26 of the conductive element of the transmission line 12 from the inner wall 22 of the metallic body 14 and the distance y of the second edge 28 of the conductive element of the transmission line 12 are equal. For example, assuming that the dielectric material is PTFE having a dielectric constant of 2.1, that the impedance required is still 50 ohm, and that the dimensions of the transmission line 12 are still the same, it will be sufficient to impose that z=y=5.65 mm.

(26) By applying simple solid geometry rules, one can obtain that the impedance has a constant value along the entire longitudinal extension of the metallic body 14. More in general, it must be ensured that the transmission line 12 is positioned centrally within the cavity 20, and that its edges 26,28 are equidistant from the inner wall 22,22 of the metallic body 14.

(27) By sliding the metallic body 14 on the transmission line 12, the electric length of the line itself will change, and so will the phase delay of a signal in transit on the transmission line 12.

(28) With reference to FIG. 3, there is shown a diagram that illustrates the effect obtained upon the transmission line 12 by the device 10 according to the invention.

(29) In a first operating position 41, the metallic body 14 is positioned in such a way that the transmission line 12 is completely immersed in the second dielectric medium, in particular PTFE, Position 41 illustrates the case wherein the phase delay of the signal in transit on the transmission line 12 is equal to zero.

(30) In a second operating position 42, a first portion of the element of the transmission line 12 is immersed in the first dielectric medium and a second portion of the transmission line 12 is immersed in the second dielectric medium.

(31) Depending on the phase delay to be obtained, e.g., 90?, the metallic body 14 is simply translated along the transmission line 12 to the desired position. The impedance of the transmission line 12 will still remain constant thanks to the geometric construction of the device 10.

(32) In a third operating position 43, the metallic body 14 is positioned in such a way that the transmission line 12 is completely immersed in the first dielectric medium, in particular air. In this position, the phase delay introduced on the signal may be, for example, 180?.

(33) In the example shown in FIG. 3, it is assumed that the first dielectric medium is air and the second dielectric medium is PTFE.

(34) It is clear that, as the first portion of the transmission line 12, immersed in the second dielectric medium, grows longer, the phase delay of the signal in transit on the transmission line 12 will increase.

(35) It is apparent from the above that implementing a delay line created by means of the device 10 and a constant-impedance transmission line 12 in a switchless combiner can be very useful.

(36) Still with reference to FIG. 2, in fact, in order to implement a line whose electric length must be varied between any two points 34,36 of a circuit 32, e.g., a printed circuit, it will be sufficient to electrically connect the points 34,36 of the circuit 32 by means of a constant-impedance transmission line comprising a transmission line portion 12 covered by the device 10 and two connecting conductive elements 37,38 that connect said points 34,36 to the transmission line portion 12 covered by the device 10.

(37) In particular, if the delay line is one of a switchless combiner, the device 10 according to the invention advantageously allows varying the phase delay of a signal present in a switchless combiner without having to replace the line thereof to comply with the ?/4 requirement. In fact, it will be sufficient to translate the device 10 along the transmission line 12 to change the electric length of the line itself; the variation of the electric length implies a phase delay of the signal running on the transmission line 12, as shown in FIG. 3.

(38) The features of the present invention, as well as the advantages thereof, are apparent from the above description.

(39) A first advantage of the switchless combiner with adjustable phase delay according to the present invention is that it can be manufactured in a simple and economical manner.

(40) A second advantage of the switchless combiner and method according to the present invention is that they can be both easily implemented in a new or an existing circuit.

(41) A further advantage of the switchless combiner and method thereof according to the present invention is that the electric length of the conductor can be adjusted without having to turn off the switchless combiner that comprises said device and/or without having to act upon at least one signal transmitter.

(42) Yet another advantage of the switchless combiner and method thereof according to the present invention is that the phase delay of a signal can be adjusted without having to modify the electric connections of the switchless combiner that comprises said device.

(43) The switchless combiner comprising a device adapted to introduce a phase delay on the electric signals in transit therein and the method thereof described herein by way of example may be subject to many possible variations without departing from the novelty spirit of the inventive idea; it is also clear that in the practical implementation of the invention the illustrated details may have different shapes or be replaced with other technically equivalent elements.

(44) For example, also the first portion 21 of the cavity 20 may be filled with a dielectric material having a cutout corresponding to the slot 24, provided that the dielectric material has a different (e.g., lower) dielectric constant than the second portion 23 of the cavity 20.

(45) For example, dielectric materials other than PTFE may be used, in particular fiberglass-based materials.

(46) For example, the present invention may be used for creating a system of signal transmitters comprising one or more circuits 32 accommodating one or more respective switchless combiners adapted to introduce a delay on one or more signals.

(47) Also, the switchless combiner may comprise one or more devices 10 as described herein, if there are one or more transmission lines 12. In other words, the device 10 may be applied to the transmission line 12 connected to the first transmitter 2 and/or to the transmission line 12 connected to the second transmitter 3. In this latter case, it will be possible to modify the phase delay either on only one of the two transmission lines 12,12 or on both transmission lines 12,12, so as to be able to appropriately modulate the power of the signals being outputted by the switchless combiner.

(48) It can therefore be easily understood that the present invention is not limited to a switchless combiner comprising a device adapted to introduce a phase delay on electric signals in transit therein, and a method thereof, but it may be subject to many modifications, improvements or replacements of equivalent parts and elements without departing from the inventive idea, as clearly specified in the following claims.