Transmission line transformers

Abstract

A transmission line transformer having a time delay network having a signal terminal and a pair of output terminals connected to the signal terminal through a corresponding one of a pair of time delay elements, the delay line elements having different time delays. A pair of transmission lines, each one having a pair of electrically coupled elements. A first one of the elements in one of the transmission lines has a first end connected to one of the pair of output terminals. A second one of the elements in such one of the transmission lines has a second end connected to a second end of one of the pair of elements in the other one of the transmission lines. The first one of the pair of elements in the other one of the pair of transmission lines is coupled to a second one of the pair of output terminals.

Claims

1. A transmission line transformer, comprising: a time delay network having a pair of output terminals connected to an input terminal through a corresponding one of a pair of time delay elements, the delay line elements having different time delays; a transmission line section comprising a pair of transmission lines, each one of the transmission lines having a pair of electrically coupled elements, a first one of the electrically coupled elements in each one of the pair of transmission lines having a first end connected to a corresponding one of the pair of output terminals of the time delay network, a second one of the electrically coupled elements in a first one of the transmission lines having a second end connected to a second end of the first one of the pair of electrically coupled elements in a second one of the pair of transmission lines; and wherein the time delay element of each one of the pair of time delay provides a predetermined time delay selected to produce: a voltage between the output end of the first one of the electrically coupled elements in the first one of the pair of transmission lines and output end of the second one of the pair of transmission lines equal to, and in phase with, a voltage produced between the output end of the first one of the electrically coupled elements in the second one pair of transmission lines and the output end of the second one of the electrically coupled elements in the second one of the pair of transmission lines.

2. The transmission line transformer recited in claim 1 wherein a second end of the first electrically coupled element of said first of the pair of transmission lines is connected to an output of the transmission line transformer.

3. The transmission line transformer recited in claim 2 wherein one end of the second electrically coupled element in said second one of the pair of transmission lines is connected to a reference terminal of the transmission line transformer.

4. The transmission line transformer recited in claim 3 wherein a first end of the second electrically coupled element in said first of the pair of transmission lines is connected to the reference terminal.

5. The transmission line transformer recited in claim 4 wherein a first end of the second electrically coupled element in said first one of the transmission lines is connected to the reference terminal.

6. A transmission line transformer, comprising: a time delay network having: an first input terminal connected to a signal terminal; a second input terminal connected to a reference terminal; and a pair of output terminals, each one of the pair of output terminals being connected to the input terminal through a corresponding one of a pair of time delay elements, the delay line elements having different time delays; a pair of transmission lines, each one of the transmission lines having a pair of electrically coupled elements; wherein a first one of the electrically coupled elements in a first one of the pair of the transmission lines has a first end connected to a first one of the pair of output terminals of the time delay line network and a second end coupled to a first one of the output terminals of the transmission line transformer; wherein a second one of the electrically coupled elements in the first one of the pair of transmission lines has a first end connected to the reference terminal and a second end connected to a second end of a first one of the pair of electrically coupled elements in a second one of the pair of transmission lines; and wherein the first one of the pair of electrically coupled elements in the second one of the pair of transmission lines is coupled to a second one of the pair of output terminals of the time delay network; and wherein the time delay element of each one of the pair of time delay provides a predetermined time delay selected to produce: a voltage between the output end of the first one of the electrically coupled elements in the first one of the pair of transmission lines and output end of the second one of the pair of transmission lines equal to, and in phase with, a voltage produced between the output end of the first one of the electrically coupled elements in the second one pair of transmission lines and the output end of the second one of the electrically coupled elements in the second one of the pair of transmission lines.

7. A transmission line transformer, comprising: a time delay network having a pair of output terminals connected to an input terminal through a corresponding one of a pair of time delay elements, the delay line elements having different time delays; a transmission line section comprising a pair of transmission lines, each one of the transmission lines having: a pair of electrically coupled elements, each one of the pair of electrically coupled elements having an input end and an output end; wherein: a first one of the electrically coupled elements in each one of the pair of transmission lines has the input end thereof connected to a corresponding one of the pair of output terminals of the network; the first one of the electrically coupled elements in the first one of the pair of transmission lines has the output end thereof connected to a first output terminal of the transmission line section; a second one of the electrically coupled elements in the first one of the transmission lines has the output end thereof connected to the output end of the first electrically coupled element of a second one of the pair of transmission lines; and the output end of the second one of the electrically coupled elements in the second one of the transmission lines is connected to a second output terminal of the transmission line section; and wherein the time delay element of each one of the pair of time delay provides a predetermined time delay selected to produce: a voltage between the output end of the first one of the electrically coupled elements in the first one of the pair of transmission lines and output end of the second one of the pair of transmission lines equal to, and in phase with, a voltage produced between the output end of the first one of the electrically coupled elements in the second one pair of transmission lines and the output end of the second one of the electrically coupled elements in the second one of the pair of transmission lines.

8. The transmission line transformer recited in claim 7 wherein the network includes a pair of amplifiers, each one of the pair of amplifiers being serially connected to a corresponding one of the pair of time delay elements.

9. The transmission line transformer recited in claim 7 wherein each one of the each one of the transmission lines is a coaxial transmission line having a center conductor and an outer conductor, and; including a dielectric structure having a upper portion disposed above a lower portion, with an electrical connector on the upper portion and an electrical connector on the lower portion electrically interconnected with an electrically conductive via passing though the upper portion, and wherein the electrical connector on the upper portion is electrically connected to the center conductor of one coaxial transmission line and the electrical connector on the lower portion is electrically connected to the outer conductor of another coaxial transmission line.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1A is a schematic diagram of a building block used in a transmission line transformer, according to the PRIOR ART;

(2) FIG. 1B is a schematic diagram of a building block used in a transmission line transformer with coaxial transmission lines, according to the PRIOR ART;

(3) FIG. 1C is a schematic diagram of a 5:1 Guanella impedance transformer using the building block of FIG. 1A, according to the PRIOR ART;

(4) FIG. 1D is a schematic diagram of a 5:1 Guanella impedance transformer using the building block of FIG. 1B;

(5) FIG. 2 is a schematic diagram of a building block used in a transmission line transformer, according to the disclosure;

(6) FIG. 3 is a schematic diagram of a 5:1 Guanella impedance transformer using the building block of FIG. 2, according to the disclosure;

(7) FIG. 4 is a schematic diagram of a 5:1 Guanella impedance transformer using the building block of FIG. 2 implemented with coaxial transmission lines, according to the disclosure;

(8) FIG. 5 is a diagrammatical plane view of the 5:1 Guanella impedance transformer of FIG. 4, according to the disclosure;

(9) FIG. 6 is a diagrammatical plane view of a transmission line section used in the 5:1 Guanella impedance transformer of FIG. 5 according to the disclosure;

(10) FIG. 6A is a cross sectional sketch of an enlarged portion of the transmission line section of FIG. 6, such enlarged portion being indicated by a circled region labeled 6A-6A in FIG. 6 according to the disclosure; and

(11) FIG. 6B is a plan view of an enlarged portion of the transmission line section of FIG. 6, such enlarged portion being indicated by a circled region labeled 6B-6B in FIG. 6 according to the disclosure;

(12) FIGS. 6C-6E are cross-sectional views of enlarged portions of the transmission line section of FIG. 6, such cross sections being taken along lines 6C-6C, 6D-6D and 6E-6E, respectively in FIG. 6; and

(13) FIG. 7 is an isometric sketch of the transmission line section of FIG. 6 according to the disclosure.

(14) Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

(15) Referring now to FIG. 2, a transmission line transformer 10 is shown having: a time delay network 12 connected to an input terminal 14. The time delay network 12 includes: a signal terminal 16 connected to the input terminal 14; a reference terminal 18, here system ground; and a pair of output terminals 22.sub.1, 22.sub.2, each one of the pair of output terminals 22.sub.1, 22.sub.2 being connected to the input terminal 16 through a corresponding one of a pair of time delay elements TD.sub.1, TD.sub.2, as shown. Each one of a pair of amplifiers AMP.sub.1, AMP.sub.2, is connected to a corresponding one of the pair of time delay elements TD.sub.1, TD.sub.2, as shown.

(16) The transmission line transformer 10 includes a transmission line section 23 having a pair of input ports 25.sub.1, 25.sub.2 connected to the outputs of the pair of amplifiers AMP.sub.1, AMP.sub.2, respectively, as shown. The transmission line section 23 includes a pair of transmission lines, TL.sub.1, TL.sub.2 each one of the transmission lines TL.sub.1, TL.sub.2 having a pair of electrically coupled elements C.sub.1, C.sub.2, here shown as a pair of mutually coupled coils. A first one of the elements C.sub.1 in a first one of the pair of the transmission lines, here transmission line TL.sub.1 has a first end E.sub.1 connected to a first one of the pair of output terminals 22.sub.1, 22.sub.2, here output terminal 22.sub.1 of the time delay line network 12 through amplifier AMP.sub.1 and a second end E.sub.2 coupled to output terminal 28 of the transmission line transformer 10. A second one of the elements C.sub.2 in the first one of the pair of transmission lines TL.sub.1 has a first end E.sub.1 connected to the reference terminal and a second end E.sub.2 connected to a second end E.sub.2 of a first one of the pair of elements C.sub.1 in a second one of the pair of transmission lines TL.sub.2 through a connector 32, as shown. The first one of the pair of elements C.sub.1 in the second one of the pair of transmission lines TL.sub.2 is coupled to the one of the pair of output terminals 22.sub.1, 22.sub.2, here output terminal 22.sub.2 of the time delay network 12 through amplifier AMP.sub.2, as shown. A second end E.sub.2 of the second element C.sub.2 of second one of the pair of transmission lines TL.sub.2 is connected to output 30 of the transmission line transformer 10, here to system ground. A first end E.sub.1 of the second element C.sub.2 in the second one of the pair of transmission lines TL.sub.2 is also connected to system ground, as indicated. A first end E.sub.1 of the second element C.sub.2 the second one of the pair of transmission lines TL.sub.2 is connected to the system ground, as shown. The delay lines TD1 and TD2 are selected so that the voltage V.sub.1 across the first transmission line TL.sub.1 is equal to, and in phase with the voltage V.sub.2 across the second transmission line TL.sub.2. In that way, the output voltage across the output terminals 28, 30 equals V.sub.1+V.sub.2; where V.sub.1=V.sub.2. As a result, the input impedance Z.sub.0 of the transmission line transformer 10 across terminals 25, 18 will be transformed to an output impedance 4Z.sub.0 across output terminals 28, 30.

(17) Referring now to FIG. 3, a transmission line transformer 10 is shown here arranged as a 5:1 Guanella impedance transformer. The transmission line transformer 10 includes a time delay network 12. The time delay network 12 includes: an first input terminal 14 connected to a signal terminal 16; a second input terminal 18 connected to a reference potential, here system ground; a plurality of N, where N is an integer greater than 1, here N=5 of time delay elements TD.sub.1-TD.sub.5; a plurality of N output terminals 22.sub.1-, 22.sub.5, respectively, each one of the five output terminals 22.sub.1-, 22.sub.5 being connected to the input terminal 16 through a corresponding one of the five time delay elements TD.sub.1-TD.sub.5, respectively, as shown. The output terminals 22.sub.1-, 22.sub.5 are connected to a corresponding one of five amplifiers AMP.sub.1-AMP.sub.5, respectively, as shown. The outputs of the amplifiers output terminals 25.sub.1-, 25.sub.5 are connected to a corresponding one of five amplifiers AMP.sub.1 are connected to a transmission line section 23, here including five transmission lines, TL.sub.1-TL.sub.5 each one of the transmission lines TL.sub.1-TL.sub.5 having a pair of electrically coupled elements C.sub.1, C.sub.2, here shown as a pair of mutually coupled coils. More particularly, the upper one of coils, C.sub.1, in each one of the transmission lines TL.sub.1-TL.sub.5 has a first, or input, end E.sub.1 connected to one of the output of the amplifier and the lower one of the coils, C.sub.2, in each one of the transmission lines TL.sub.1-TL.sub.5 has a first end E.sub.1 connected to system ground. The second end, E.sub.2, of the lower coil, C.sub.2 in transmission line TL.sub.1 is connected to a second end E.sub.2 of the upper coil C.sub.1 in the next one of the transmission lines, here transmission line TL.sub.2 through a connector 32.sub.1; the second end, E.sub.2, of the lower coil, C.sub.2 in transmission line TL.sub.2 is connected to a second end E.sub.2 of the upper coil C.sub.1 in the next one of transmission line, here transmission line TL.sub.3 through a connector 32.sub.2; the second end, E.sub.2, of the lower coil, C.sub.2 in transmission line TL.sub.3 is connected to a second end E.sub.2 of the upper coil C.sub.1 in the next one of the transmission line, here transmission line TL.sub.4 through a connector 32.sub.3; the second end, E.sub.2, of the lower coil, C.sub.2 in transmission line TL.sub.4 is connected to a second end E.sub.2 of the upper coil C.sub.1 in the next one of the transmission lines, here transmission line TL.sub.4 through a connector 32.sub.4. The second end E.sub.2 of the upper coil C.sub.1 of transmission line TL.sub.1 provides an output terminal of the Guanella impedance transformer and the second end E.sub.2 of the lower coil C.sub.2 of transmission line TL.sub.5 is connected to output terminal 30, here at system ground, as shown. With such an arrangement, the voltage produced across the output terminals of each of the transmission lines, TL.sub.1-TL.sub.5 will be V.sub.1-V.sub.5, respectively, as indicated. The delay lines TD.sub.1-TD.sub.5 are selected so that the voltage V.sub.1 across the first one of the transmission lines TL.sub.1 is equal to, and in phase with the voltage V.sub.2 across the second one of the transmission line TL.sub.2; the voltage V.sub.3 across the third transmission line TL.sub.3 is equal to, and in phase with the voltage V.sub.2 across the second transmission lines TL.sub.2; the voltage V.sub.4 across the fourth transmission lines TL.sub.4 is equal to, and in phase with the voltage V.sub.3 across the third transmission lines TL.sub.3; the voltage V.sub.5 across the fifth transmission lines TL.sub.5 is equal to, and in phase with the voltage V.sub.4 across the fourth transmission lines TL.sub.4. In that way, the output voltage across the output terminals 28, 30 will equal V.sub.1+V.sub.2+V.sub.3+V.sub.4+V.sub.5; where V.sub.1=V.sub.2=V.sub.3=V.sub.4=V.sub.5, and the input impedance Z.sub.0 of the transmission line transformer 10 across terminals 16, 18 will be transformed to an output impedance 25Z.sub.0 across output terminals 28, 30.

(18) Referring to FIG. 4, here the transmission line transformer 10 of FIG. 3 is shown implemented with coaxial transmission line TL.sub.1-TL.sub.5. It is noted that the time delay elements TD.sub.1-TD.sub.5, may be placed either before or after the amplifiers AMP.sub.1-AMP.sub.5, respectively as indicated. A more detailed description of the transmission line transformer 10 of FIG. 5 is shown. Thus, as shown, the time delay network 12 is here a microstrip transmission line circuit having a dielectric board 30 having a ground plane conductor, not shown, on the bottom of the board 30 with a plurality of, here five strip conductors of different lengths to on the top of the board 30 to provide the five time delay elements TD.sub.1-TD.sub.5. The outputs of the five time delay elements TD.sub.1-TD.sub.5 are coupled to a corresponding one of the five amplifiers AMP.sub.1-AMP.sub.5, as shown. Here, each one of the five amplifiers AMP.sub.1-AMP.sub.5, is formed as a separate monolithic microwave integrated circuit (MMIC). That is, here each one of the five amplifiers AMP.sub.1-AMP.sub.5, is formed on a separate integrated circuit chip.

(19) One method which may be used to determine the time delays TD1-TD5 is as follows: During a calibration/testing or simulation procedure, after construction of the transmission line section 23 with the outputs of the transmission lines TL1-TL5 electrically interconnected one to the other as shown and as described above, the requisite time delay from the first end E1 of first one of the electrically coupled elements C1 in each one of the transmission lines TL1-TL5 to the output 28 of the transmission line section 23 is determined. Once determined, the time delay network 30 is constructed with the time delays TD1-TD5 having a proper physical length such that the time delays produce predetermined time delays determined during the calibration/testing procedure. It is noted that time delays TD1-TD5 here, in this example, have different electrical lengths; however, the electrical lengths from the input port 14 to the first ends E1 of the first elements C1 of the transmission lines TL1-TL5 are proper to produce the proper output voltage across the output terminals 28, 30; that is V.sub.1+V.sub.2+V.sub.3+V.sub.4+V.sub.5; where V.sub.1=V.sub.2=V.sub.3=V.sub.4=V.sub.5, as shown in FIG. 3. The outputs of the five amplifiers AMP.sub.1-AMP.sub.5 are fed to the transmission line section 23. The transmission line section 23, shown in more detail in FIGS. 6 and 6A, includes a pair of microstrip transmission line sections 34, 36. Microstrip transmission line section 34 includes a dielectric board 38 having a ground plane conductor, not shown, on the bottom of the board 38, a plurality strip conductors on the top of the board 38 to provide the input ports 25.sub.1-25.sub.5, and a conductor 39 which is connected to a ground plane conductor 54 which extends from the bottom of the board 38. Microstrip transmission line section 36 includes a dielectric board 40 having a ground plane conductor, not shown, on the bottom of the board 40 with two strip conductor layers, one on the top of the board 40 and one embedded in board 40. The top layer provides output port 28.

(20) Disposed between the pair of microstrip transmission line sections 34, 36 are the transmission lines TL.sub.1-TL.sub.5, here each one being a coaxial transmission line having a pair of coupling elements. C.sub.1, C.sub.2, element C.sub.1 being the inner conductor of the coaxial transmission line and element C.sub.2 being the outer conductor of the coaxial transmission line. Each one of the first ends E.sub.1 of the elements C.sub.1 is connected to a corresponding one of the input ports 25.sub.1-25.sub.5, and each one of the first ends E.sub.1 of the elements C.sub.2 is connect to the conductor 39. It is noted that the conductor 39 is electrically isolated from the input ports 25.sub.1-25.sub.5 by the dielectric board 38, as shown more clearly in FIGS. 6 and 6A, where FIG. 6A shows an exemplary one of the transmission lines TL.sub.1-TL.sub.5, here transmission line TL.sub.5. The second end E.sub.2 of coupling elements C.sub.1 of transmission line TL.sub.1 is connected to output port 28, as shown. The second end E.sub.2 of coupling elements C.sub.2 of transmission line TL.sub.1 is connected to the second end E.sub.2 of coupling element C.sub.1 of transmission line TL.sub.2 by a conductor 32.sub.1 disposed on the dielectric board 40. The second end E.sub.2 of coupling elements C.sub.2 of transmission line TL.sub.2 is connected to the second end E.sub.2 of coupling element C.sub.1 of transmission line TL.sub.3 by a conductor 32.sub.2 disposed on the dielectric board 40. The second end E.sub.2 of coupling elements C.sub.2 of transmission line TL.sub.3 is connected to the second end E.sub.2 of coupling element C.sub.1 of transmission line TL.sub.4 by a conductor 32.sub.3 disposed on the dielectric board 40. The second end E.sub.2 of coupling elements C.sub.2 of transmission line TL.sub.4 is connected to the second end E.sub.2 of coupling element C.sub.1 of transmission line TL.sub.5 by a conductor 32.sub.4 disposed on the dielectric board 40. The second end E.sub.2 of coupling elements C.sub.2 of transmission line TL.sub.5 is connected to a conductor 41 on the top of dielectric 40; the conductor 41 being electrically isolated from output port 28, and the conductors 32.sub.1-32.sub.4 by portions of the dielectric board 40. Conductors 39 and 41 are both connected to system ground. Here, the transmission lines TL.sub.1 and TL.sub.2 are disposed within a hollow ferrite core 50.sub.1 and transmission lines TL.sub.3 and TL.sub.4 are disposed within a hollow ferrite core 50.sub.2, as shown.

(21) FIG. 6A shows the first end E1 of the coupling elements C.sub.1 and C.sub.2 of an exemplary one of the transmission lines TL.sub.1-TL.sub.5, here transmission line TL.sub.5. The first end E1 of coupling element C.sub.1, here the center conductor of the coaxial conductor of transmission line TL.sub.5 is connected input port 25.sub.5 of the transmission line section 23 and the first end E1 of the coupling element C.sub.2, here the outer conductor of the coaxial conductor of TL.sub.5 is connected to conductor 54 on dielectrics board 38. It is noted that the center conductor, coupling element C1 is physically separated by a dielectric 51 from the coupling element C.sub.2; however at microwave frequencies the center conductor coupling element C.sub.1 and outer conductor coupling element C.sub.2 are electrically coupled by the electric field of the microwave energy passing through the coaxial transmission line. It is noted that the conductor 39 is electrically isolated from the port 25.sub.5 by region 52. It is also noted that the ground plane conductor on the bottom of dielectric 38, mention above, is here shown as conductor 54 and is connected to conductor 39.

(22) More details of the connections of the center conductor coupling elements C1 to the outer conductor coupling element C.sub.2 of the transmission lines TL1-TL5 are shown in FIGS. 6B through 6E. It is first noted that because the center conductor coupling elements C1 and the outer conductor coupling element C.sub.2 are at two different elevations; the a dielectric board 40 is constructed has an upper portion 40U and a lower portion 40L as indicated in FIG. 6B and that the connectors 32.sub.1-32.sub.4 each has two sections 32a, 32b; section 32a being on top of board 40U and section 32b being on board 40L, the two sections 32a and 32b being electrically connected by conductive vias 32c, as shown more clearly in FIG. 6E. Thus, sections 32a are connected to the center conductor coupling elements C1; sections 32b are connected to the outer conductor coupling element C.sub.2 and the two are electrically connected by the conductive vias 32c. Also the outer conductor coupling element C.sub.2 of transmission line TL5 is connected to the ground plane conductor 54 through a conductor 60 and conductive vias 62, as shown in FIG. 6D.

(23) FIG. 7 is an isometric view of the transmission line transformer 10.

(24) A number of embodiments of the disclosure have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. For example, in some applications, the ferrite cores need not be required. Further, the number of transmission line sections may be greater or less than 5. Accordingly, other embodiments are within the scope of the following claims.