US3745488A

US3745488A - Microwave impedance-matching network

Info

Publication number: US3745488A
Application number: US00194383A
Authority: US
Inventors: R Rogers
Original assignee: GTE Automatic Electric Laboratories Inc
Current assignee: AG Communication Systems Corp
Priority date: 1971-02-16
Filing date: 1971-11-01
Publication date: 1973-07-10
Anticipated expiration: 1990-07-10

Abstract

In preferred form, a matching network includes a transmission line comprising a pair of parallel inner conductors symmetrically located in an outer conductor enclosure for supporting odd and even modes of propagation. Impedances to be matched are connected between adjacent one ends of the inner conductors and the enclosure. First and second sections of the transmission line, measured from the one ends of the conductors, are formed by short circuiting the inner conductors together and both inner conductors to the enclosure, respectively, at points that are spaced from the one ends of the conductors. The first transmission line section supports both the even and odd modes of propagation while the second line section primarily supports only the even mode of propagation. The positions of the short circuits are moved along the inner conductors in order to match the impedances. In an alternate embodiment, the network includes a pair of parallel inner conductors symmetrically located in a first cylindrical conductor, the latter being coaxially supported in a second cylindrical conductor. First and second sections of short circuited transmission line are formed by short circuiting the cylinders together and by short circuiting both inner conductors to the first cylinder, respectively. The positions of the short circuits are separately moved along the cylinders in order to match impedances that are connected between associated inner conductors and the second cylinder. Stripline versions of these networks are also disclosed.

Description

United States Patent 1191 Rogers 1451 July 10,1973

[ MICROWAVE IMPEDANCE-MATCHING NETWORK [75] Inventor: Robert G. Rogers, Los Altos, Calif.

[73 Assignee: GTE Automatic Electric Laboratories Incorporated, Northlake, Ill.

[22] Filed: Nov; 1, 1971 [21] Appl. No.: 194,383

Related US. Application Data [63] Continuation-impart of Ser. No. [15,449, Feb. 16,

1971, Pat. N0. 3,699,475.

Barrett-Microwave Printed CircuitsA Historical Review in IRE Transactions on Microwave Theory & Techniques Volume M'IT-3, March 1955; pp. 1-3 & 6 1

Primary Examiner-Rudolph V. Rolinec Assistant Examiner-Marvin Nussbaum Attorney- K. Mullerheim, Leonard R. Cool et al.

[5 7 ABSTRACT In preferred form, a matching network includes a transmission line comprising a pair of parallel inner conductors symmetrically located in an outer conductor enclosure for supporting odd and even modes of propagation. Impedances to be matched are connected be tween adjacent one ends of the inner conductors and the enclosure. First and second sections of the transmission line, measured from the one ends of the conductors, are formed by short circuiting the inner conductors together and both inner conductors to the enclosure, respectively, at points that are spaced from the one ends of the conductors. The first transmission line section supports both the even and odd modes of propagation while the second line section primarily supports only the even mode of propagation. The positions of the short circuits are moved along the inner conductors in order to match the impedances. In an alternate embodiment, the network includes a pair of parallel inner conductors symmetrically located in a first cylindrical conductor, the latter being coaxially supported in a second cylindrical conductor. First and second sections of short circuited transmission line are formed by short circuiting the cylinders together and by short circuiting both inner conductors to the first cylinder, respectively. The positions of the short circuits are separately moved along the cylinders in order to match impedances that are connected between associated inner conductors and the second cylinder. Stripline versions of these networks are also disclosed.

16 Claims, 7 Drawing Figures PATENTEU JUL 1 0 SHEU 1 (IF 3 INVENTOR. ROBERT G. ROGERS BY W 44 AGENT PATENIEUJUL 1 mm SHEU 2 BF 3 INVENTOR. ROBERT G. ROGERS BY Mfi AGENT MICROWAVE IMPEDANCE-MATCHING NETWORK REFERENCE TO COPENDING APPLICATION This case is a continuation-in-part of my copending U.S. Pat. application, Double-Mode Tuned Microwave Oscillator, Ser. No. 115,449, filed Feb. 16, 1971 now U.S. Pat. No. 3,699,475, issued Oct. 17, 1972.

BACKGROUND OF INVENTION This invention relates to tuning circuits and more particularly to a tunable microwave impedance matching network.

An impedance matching network is a two-port device that is employed to transform a given value of impedance connected across one port to a different value of impedance connected across the other port or to match two given impedances having different values. Such networks are often made adjustable in order to transform the value of the given impedance into whatever value of impedance is required, e.g., so as to produce maximum output power from an oscillator including a semiconductor device in which wide electrical tolerances are common. Prior art adjustable impedance matchingnetworks include dielectric slugs in a coaxial transmission line, a coaxial transmission line having a movable eccentric center conductor, and tuning stubs short circuited across a transmission line. The former two matching networks are limited in the range of impedances that can be matched. The triple-stub tuner comprises three short circuited stubs that are spaced a quarter wavelength apart along a transmission line at the operating frequency of the tuner. Although this tuner is commonly usedfor impedance matching, it has the disadvantage of being a fixed frequency device for operating at a single frequency or over a very narrow band of frequencies. A physically different tuner is required to match the same impedances at a different frequency. Also, tuning of this prior art device is complicated by the fact that there are three controlsor plungers to adjust, of which two may be maintained equal. Thus, it is necessary to vary three separate controls or to gang two of the plungers together.

An object of this invention is the provision of an improved impedance matching network.

Another object is the provision of an impedance matching network capable of matching impedances over a broad range of impedance values and over a broad band of frequencies.

SUMMARY OF INVENTION Briefly, two short circuited transmission line sections, at least one of which supports both 'odd and even modes of propagation, are electrically connected at one ends thereof that are spaced from the short circuits. Two impedances to be matched are connected across conductors of the line sections at their connection point. The impedances are matched by changing the positions of the short circuits and thus the lengths of the line sections between the impedances and the short circuits.

DESCRIPTION OF DRAWINGS This invention will be more fully understood from the following detailed description thereof, together with the drawings in which:

FIG. 1 is a perspective view of a preferred embodiment of this invention with the top and side walls partically cut away to show the internal construction thereof;

FIG. 2 is a perspective view of a stripline version of the tuner in FIG. 1 with top plates broken away to show the internal construction thereof;

FIG. 3 is a schematic circuit diagram representing the electrical equivalent circuit of the tuner in FIG. 2 with a load admittance Y connected thereto;

FIG. 4 is a perspective view of an alternate embodiment of this invention with the outer conductor cut away to show the internal construction thereof;

FIG. 5 is a greatly enlarged top view, mostly in section, of another embodiment of this invention;

FIG. 6 is a schematic circuit diaphragm representing the electrical equivalent circuit of the tuner in FIG. 5 with a load admittance Y, connected thereto; and

FIG. 7 is an exploded section view of the stripline version of the tuner in FIG. 5.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to FIG. 1, a preferred embodiment of this invention comprises a pair of metal rod conductors 4 and 5 that are mounted in a square metal box or enclosure 6 which is a ground plane. The enclosure may also be cylindrical. The rod conductors preferably are of the same diameter and symmetrically located in the enclosure 6, although this is not necessary. This tuner is a two port network having ports corresponding to the

coaxial connectors

7 and 8 that are mounted on the end wall 9 of theenclosure. The connectors are connected to the one ends of associated conductors 4 and 5 and wall 9. The other ends of the conductors are supported in the end wall 10 of the enclosure.

The conductors 4 and 5 are short circuited together at a distance I, from the end wall 9 by a metal rod 12 having conductive sleeves l4 and 15 connected to the ends thereof. These sleeves are coaxial with the conductors 4 and 5. Spring fingers on sleeves l4 and 15 electrically contact the associated conductors 4 and 5. The conductors are also short circuited together and to enclosure 6 at a distance 1 1 from end wall 9 by a movable wall 16. Spring fingers 17 on the movable wall contact the ground plane enclosure 6.

Metal sleeves

18 and 19, which are mounted in wall 16 coaxial with conductors 4 and 5, respectively, have spring fingers which provide a sliding electrical contact with the associated conductors.

This transmission line comprising conductors 4 and 5 and the enclosure 6 supports both even and odd modes of propagation. The conductors 4and 5 for the even mode have currents thereon that are in phase at adjacent points across the conductors, i.e., the conductors are everywhere at the same potential for the even mode. The currents for the odd mode, however, are out-of-phase at adjacent points across conductors 4 and 5. Thus, the short circuit produced by rod 12 has no effect on the even modes on conductors 4 and 5. Rod 12 is a short circuit, however, for the odd mode. Rod 12 and the length 1 of transmission line are referred to as an odd mode short circuit and an odd mode transmission line, respectively, although this length 1 of line actually supports both odd and even modes. The length I, of line, however, normally only supports even modes. Since wall 16 short circuits conductors 4 and 5 together as well as to the ground plane 6, the movable wall 16 is a combination odd and even mode short circuit. The wall 16 and length 1, +1 of transmission line are referred to hereinafter, however, as an even mode short circuit and an even mode transmission line, respectively.

A rod 21 is rigidly connected to wall 16 for moving the latter wall and thereby changing the position of the even mode short circuit and the length 1 of the conductors. A rod 22 extends through the walls and 16 of the enclosure and is centered between conductors 4 and 5. The rod 22 is rigidly secured to rod 12 and is used to change the position of the odd mode short circuit produced by the latter and the length 1 of the odd mode transmission line. Although moving rod 12 causes the lengths l and of conductors 4 and 5 to both vary, this is not a problem in practice since the two controls are adjusted together to match impedances connected to the

coaxial connectors

7 and 8. The rod 12 has the advantage of suppressing undesirable odd mode resonances that might occur on the conductors between the short circuits provided by rod 12 and wall 16 when the length 1 of line is a half wavelength long at the operating frequency of the tuner. The rod 22 may be made of electrically conductive or dielectric material. Alternatively, rod 22 may be a conductor contacting both conductors 4 and 5 over the lengths 1 thereof between rod 12 and wall 16.

In a tuner for operating over a broad band of frequencies, the lengths l and 1 of transmission line are preferably each made a half wavelength long at the lowest frequency of operation. The tuner can then be employed to match any impedances at frequencies greater than this initial lowest design frequency value since all possible values of impedance may be obtained with a transmission line section that is a half wavelength long.

In operation, the impedances to be matched by the network in FIG. 1 are connected to

connectors

7 and 8, i.e., between conductors 4 and 5 and the ground plane 6. The network is tuned to match these impedances by physically moving the positions of the

short circuit elements

12 and 16 along the conductors. Since the values of the impedances that are to be matched may be unknown, adjustment of the lengths l and 1 of conductors 4 and 5 is made by moving

elements

12 and 16 so as to give a desired result such as maximum power output of an oscillator or amplifier as indicated on a power meter.

Referring now to FIG. 2, a stripline version of the tuner in FIG. 1 is shown wherein similar elements are designated by primed reference characters in FIG. 2. This stripline tuner comprises a pair of stripline conductors 4' and 5' formed on a lower dielectric block 26 which has a bottom ground plane plate 27 secured thereto. The top section 28 of this tuner comprises an upper dielectric block 29 having a top ground plane plate 30 bonded thereto. Section 28 is placed over the conductors 4' and 5 and secured to the lower dielectric block, e.g., by screws (not shown). Metal plates 31,

' 32 and 33, 34 (the latter plate 34 not shown) are bonded to the sides of the associated dielectric blocks 26 and 29. The two

ground plane plates

27 and 30 are electrically interconnected through side plates 31 34. The conductors 4 and 5' areparallel to each other and

ground plane plates

27 and 30. An odd mode short circuit is formed on conductors 4' and 5' at a distance 1 from the one end 35 of the dielectric blocks by a thin metal strip 12' which is spaced away from the metal side'plates 31 34. The conductors are also short circuited together and to the ground planes at a distance 1 from the short circuit element 12' by a thin metal strip 16 to form an even mode short circuit. The metal strip 16 contacts both of the conductors 4' and 5' and the side plates 31 34. Impedances that are to be matched by the network are connected to ports 7' and 8, i.e., between conductors 4' and 5 and

plates

27 and 30.

The network is tuned to match these impedances connected to ports 7 and 8' by moving the position of the short circuiting metal strips 12' and 16 along conductors 4' and 5'. In this stripline tuner, the top section 28 thereof must be removed to change the positions of the short circuits. Alternatively, a modified form of the strip transmission line tuning devices disclosed in U.S. Pat. No. 3,210,697 by B. H. Comstock may be employed to accomplish this function.

The operation of an impedance matching network embodying this invention will now be analyzed in relation to a microstrip transmission line device similar to the stripline device in FIG. 2 wherein the dielectric is air. The electrical equivalent circuit of the tuner in FIG. 2 and an air-dielectric microstrip transmission line tuner is a symmetrical w

circuit comprising elements

41, 42 and 43, as illustrated in FIG. 3. The admittances Y, and Y of the associated

elements

41 and 42 are identical for a physically symmetrical microstrip circuit (where the line conductors are of the same size and equally spaced from ground planes 27 and 30) and are representable as where Y is the even mode characteristic admittance of the transmission lines, 0 B1 0 B1 0 and 0 are the electrical lengths of the associated transmission lines, [3 Z rr/A, 1r is a constant, A is the wavelength at the frequency at which the network is to operate, and B is the susceptance of the element 41. The admittance Y of the element 41 is purely imaginary since the odd and even mode lines are assumed to be losslessv Since the lengths l, and 1 of transmission line are physically and electrically short at microwave frequencies, this is a resonable assumption. A nonsymmetrical microstrip circuit, e.g., where the parallel conductors are of different sizes, would be defined by an unsymmetrical 1r circuit in which the values of the admittances Y and Y were unequal.

The admittance Y of element 43 is representable as where Y, is the odd mode characteristic admittance of the transmission lines and B is the susceptance of element 43. The characteristic admittances Y and Y of the transmission lines are related to the size and spacing of the conductors 4 and 5 with respect to the ground plane enclosure and are calculated in a manner known in the prior art.

Assuming that a load 44 is connected across port 8 for example, the inputadmittance Y, across the other port 7' is are solved to obtain definitions of the susceptances B and B and are representable as i and a i 1/ i L[( t+ 1 t HQ/ 1. t

The quantities underthe radicals in equations (4 and (5) are never negative since the conductances G, and 6,, must both be either positive or negative, i.e., of the same sign. This is because an impedance matching network withpurely reactive elements does not convert a positive impedance to a negative impedance and vice versa. Thus, no matter what the value of the load admittance Y it will be matched or transformed to the desired input admittance Y When the given values of the load admittance Y and the desired value of the input admittance Y, are known, for example, the susceptances B and B can be determined from equations (4) and (5 The physical lengths l and 1 of transmission lines required to transform the admittance Y to the admittance Y, can then be determined from equations (1) and (2). Although these equations indicate that a change in the length of either I, or 1 changes both of these susceptances B and B this is no problem in practice since the lengths l and 1 of line are both adjusted together to match theadmittances Y and Y,. The foregoing equations are particularly useful in defining a matching network for operating over a small range of impedances and frequencies.

By way of example, in an impedancematching network similar to that illustrated in FIG. 1 that was built and tested, the rods 4 and 5 were symmetricallylocated in a square enclosure 6 having inner dimensions of 0.55 by 0.55 inch, the diameters of the rods were 0.125 inch, and the center-to-center spacing of the rods was0.208 inch. The odd and even mode characteristic admittances Y and Y of this experimental tuner were 15.4 m mho and 6.9 m mho (i.e., 65 ohm and 145 ohm), respectively. These values were calculated using equations in "Coupled-Strip-Transmission-Line Filters and Directional Couplers by E. Jonesand J. Bolljahn, [RE Transactions on Microwave Theory and Technology, Vol. MTT-4, pp. 75-8l, April 1956. These admittance values were verified by operating the circuit with a known load impedance 2,, connected to port 7, moving the

short circuits

12 and 16 to adjust the lengths l and 1,, of line until the desired input impedance Z, was indicated on a meter connected to the other port 8, measuring the line lengths l and I and solving equations (1) and (2) for the admittances Y and Y,,,,. The results obtained by these two methods were in reasonable 5 agreement indicating that the equations satisfactorily define the operation of the tuner. This tuner operated satisfactorily over a 2 l bandwidth from 1 GHz to 2 GHz while matching impedances over a broad range of impedance levels as shown by the Hewlett-Packard 8410A Network Analyzer.

. Referring now to FIG. 4, a tuner embodying a modified form of this invention comprises a pair of

rod conductors

47 and 48 thatare symmetrically supported in a cylindrical enclosure 49 by a fixed end wall 50 and a dielectric spacer (not shown). A pair of

lines

51 and 52 define the two

ports

53 and 54 of the tuner to which impedances to bematched are connected.

Lines

51 and 52 are electrically connected to

conductors

47 and 48, respectively, on line AA which is orthogonal to the longitudinal axis of the enclosure. The lines. 51 and 52 are insulated from the enclosure by dielectric spacers (not shown). The dielectric

spacer supporting conductors

47 and 48 in the enclosure may be located, for example, adjacent to

lines

51 and 5 2.

A first short circuit isformed on

conductors

47 and 48 by a U-shaped conductive element 55 which is insulatedfrom enclosure 49 and spaced a distance 1 from the line AA. The

hollow arms

56 and 57 of element 55 extend over the ends of

conductors

47 and 48, respectively, to form a trombone-like sliding structure for adjustingthe length l of transmission line between element 55 and line A-A. Spring fingers on the

arms

56 and 57 make electrical connection to the associated

conductors

47 and 48. A rod 58 extends through the endwall 59 of theenclosure and is secured to element 55. The rod 58 is used tochange the position of the first or odd mode short circuit on

conductors

47 and 48. Rod58 is preferably made of a dielectric material.

A second shortcircuit is formed on

conductors

47 and 48 bya movable wall 60 in theenclosure. The wall 60 is electrically conductive and has spring fingers contacting the inner wall of the enclosure and both of the

conductors

47 and 48. A rod 61 extends through end wall '50 andis secured to wall 60. The rod 61 is used to change the positionof the second short circuit and thus to adjustthe length], of transmission line between wall 60 and line A-A. The lengths l and l, of transmission line, which bothsupport odd and even modes, are varied by moving the

short circuit elements

55 and 60 in order to match impedances connected to

ports

53 and 54. The operation of the tuners in FIGS. 1 and 4 are defined by different design equations.

Referring now to FIG. 5, a concentric tuner embodying an alternate form of this invention comprises a pair of

conductive rods

65 and 66 that are symmetrically supported in an inner electrically conductive hollow cylinder 68 (e.g., by dielectric spacers, not shown). The inner cylinder 68 is centered in an outer electrically conductive hollow cylinder 69 (e.g., by dielectric spacers, not shown). The

conductor rods

65 and 66 ex- ;tend in both directions in the

extensions

71 and 72 of the outer cylinder 69 where they are connected to

coaxial connectors

73 and 74, respectively, to form a structure that can be connected in series with coaxial transmission line devices. A more compact tuner structure may be made by omitting the two

coaxial line sections

71 and 72, placing miniature connectors at the ends of the

lines

65 and 66, and closing the section 70 with an end plate (not shown) on line BB which is electrically connected to the outer conductor 69, is insulated from cylinder 68, and is the mounting plate and ground plane for the miniature connectors. The lengths of

conductors

65 and 66 beyond the line BB are to facilitate connection thereto to external coaxial devices.

The dimensions and spacings of elements in the sections 70 72 are related to th characteristic impedances of the transmission lines thereof as is known in the art. The outer cylinder 69 may have a taper (not shown) over a portion of the length thereof adjacent the junction of section 70 and

sections

71 and 72 when the dimensions of these sections are different.

An electrically conductive disc 76 is located in the central opening of the inner cylinder 68. Spring fingers on disc 76 contact both of the

conductors

65 and 66 and the inner cylinder to form a combination odd and even mode short circuit defining a length 1 of transmission line. A rod 77 is connected to the disc 76 and is employed to change the position of the short circuit produced by the latter and thus to change the length 1 of transmission line. An electrically conductive ring 78 is located in the opening between the

cylinders

68 and 69. Spring fingers on ring 78 contact the adjacent surfaces of the cylinders. Thus, ring 78 is effectively a short circuit defining a length 1 of coaxial transmission line. Push

rods

79 and 80 which are secured to a bar 81 and the ring 78 provide a convenient mechanism for moving the short circuit element 78 and changing the length 1 of transmission line. The position of the

short circuit elements

76 and 78 and the lengths of the associated line sections are varied to match impedances connected to the coaxial connectors or

ports

73 and 74.

The operation of the tuner in FIG. 5 will now be described in relation to the electrical equivalent circuit thereof in FIG. 6 wherein the points 83 86, inclusive, in the latter correspond to points designated by primed reference characters in FIG. 5. A transmission line represented by the line of length 1 is described in Microwave Filters, Impedance Matching Networks, and Coupling Structures by G. Matthaei, L. Young and E. Jones, McGraw-Hill Book Company, New York, 1964, pp. 225. The electrical equivalent circuit of this length 1 of transmission line is a symmetrical 1r

circuit comprising elements

87, 88 and 89 between

points

83 and 84 on the conductors, with respect to the inner sheath 68 and point 85' thereon. The admittances Y, and Y of

elements

87 and 88, respectively, are the same for a strictly symmetrical circuit and are representable as Y, Y jY,, cot [31,, +jB

where Y is the even mode characteristic admittance of the length 1 of this transmission line. The admittance Y of element 89 is representable as cuit of the length 1 of transmission line, which is essentially a short circuited coaxial transmission line comprising the inner and outer cylinders, is an element 90 having an admittance Y connected between the inner and outer cylinders, i.e., between the points and 86. The admittance Y,, is representable as 0 j 06 cot B s +1 0 where Y is the characteristic admittance of the length I, of coaxial transmission line.

The 1r

circuit comprising elements

87, 88 and 89 can be transformed to a first equivalent Tcircuit connected to point 85. The element 90 and the element of the first equivalent T circuit in series therewith can then be represented by a single element to form a second threeelement equivalent T circuit. The latter T circuit can be represented as a second equivalent three-element 1r circuit having a load 91 connected across it to provide an equivalent circuit similar to that in FIG. 3. Equations for this second equivalent 1r circuit that are similar to equations (1) (5) can then be derived. These new equations will define the operation of the tuner in FIGS. 5 and 6, as was described above in relation to FIG. 3.

A stripline version of the tuner in FIG. 5 is illustrated in FIG. 7 in an exploded cross section and comprises an inner section 93 and upper and lower

outer sections

94 and 95, respectively. The inner section 93 is similar to the stripline tuner in FIG. 2 except that the metal strip 12' is omitted in FIG. 7. The upper section 94 com prises a dielectric block 96 having a conductive top ground plane plate 97 and

conductive side plates

98 and 99 bonded thereto. The lower section comprises the dielectric block 100 having a longitudinal groove 101 therein for receiving the inner section 95. A conductive bottom ground plane plate 102 and

conductive side plates

103 and 104 are bonded to dielectric block 100. A metal strip 105 is located between the

outer sections

94 and 95 and extends over thewidth of the latter for short circuiting the ground plane of the inner section to the ground plane of the outer section. This device must also be disassembled to change the position of the short circuits therein and thus to accomplish tuning thereof.

Although this invention has been shown as described in relation to preferred embodiments thereof, variations and modifications thereof will be apparent to those skilled in the art. For example, the lengths of appropriate lines may be formed of any transmission line capable of supporting odd and even modes of propagation. Also, unwanted odd mode resonances that may occur on the length 1 of the conductors in FIG. 1, for example, may be suppressed by placing an additional short circuit such as a metal clip between conductors 4 and 5 approximately halfway between rod 12 and wall 16. A nonsymmetrical network may also be produced, for example to match a very high impedance to a very low impedance, by employing conductors 4 and 5 having different diameters or which are nonsymmetrically located in an outer conductor. Such a network would be defined by an unsymmetrical 1r circuit similar to that in FIG. 3 wherein values of the admittances Y, and Y, would be unequal. Any of the networks in FIGS. 1, 4 and 5 may also have outer conductors with square or circular cross sections. The short circuit spaced I Z from

connectors

7 and 8 may also be produced by omitting wall 16 and terminating conductors 4 and 5 in an open circuit spaced Z H4 from the connectors. The scope and breadth of this invention is therefore to be determined from the following claims rather than the above detailed description.

What is claimed is:

1. Transmission line apparatus geometrically configured for supporting both odd and even mode electromagnetic waves for matching a first impedance to a second impedance, comprising first and second parallel conductors;

a conductive ground plane enclosure supporting said parallel conductors therein; said conductors being oriented in said enclosure with respect thereto for supporting odd and even modes therebetween, said parallel conductors having one ends thereof for connection to associated impedances to be matched;

means for connecting the first and second impedances between said adjacent one ends of said first and second conductors, respectively, and said enclosure;

a movable wall of said enclosure electrically shortcircuiting said parallel conductors together and to said enclosure for providing a first short circuit;

the lengths of parallel conductors between the one ends thereof and said wall defining a length of transmission line of adjustable length primarily supporting over its length only even modes;

a third conductor electrically movably contacting both of said parallel conductors at second adjacent points thereon between said one ends thereof and said wall for providing a second short circuit, the length of parallel conductors between the one ends thereof and said third conductor defining a length of transmission line of adjustable length supporting both even and odd modes; and

a rod extending slidably through said wall and between said parallel conductors and being connected to said third conductor for moving the position of the latter and the second short circuit provided thereby along said parallel conductors.

2. Transmission line apparatus geometrically configured for supporting both odd and even mode electromagnetic waves for matching a first impedance to a second impedance, comprising first and second parallel conductors;

a fourth conductor electrically connecting and shortcircuiting said parallel conductors together and being located approximately intermediate said wall and said third conductor.

3. Transmission line apparatus geometrically configured for supporting both odd and. even mode electromagnetic waves for matching a first impedance to a second impedance, comprising first and second parallel conductors that are rods having unequal diameters;

a conductive ground plane enclosure supporting said parallel conductor rods therein; said conductor rods being oriented with respect to said ground plane enclosure for supporting odd and even modes therebetween, said parallel conductor rods having first adjacent points thereon for connection to the associated impedances to be matched;

first means electrically short-circuiting said parallel conductor rods together; and

second means electrically short-circuiting said parallel conductor rods together and to said ground plane;

the positions of said first and second short circuits provided by said first and second short-circuiting means being independently movable along said parallel conductor rods for tuning the apparatus.

4. An impedance matching network comprising a first transmission line section supporting a combination of odd and even modes and comprising lengths of a first ground plane and a pair of parallel conductors;

a second transmission line section;

first and second means producing short circuits on said first and second transmission line sections, respectively, for defining the electrical lengths of the associated line sections; and

means for connecting impedances to be matched to each of said line sections at adjacent points that are spaced away from the ends of associated parallel conductors thereof.

5. An impedance matching network comprising a first transmission line section supporting a combination of odd and even modes and comprising lengths of a first ground plane and a pair of parallel conductors;

a second transmission line section comprising a second ground plane oriented with respect to said first ground plane for supporting electromagnetic fields therebetween;

first and second means producing short circuits on said first and second transmission line sections, respectively, for defining the electrical length of the associated line sections; and

means for connecting impedances to be matched t each of said line sections.

6. An impedance matching network comprising a first transmission line section supporting a combination of odd and even modes and comprising lengths of a first ground plane enclosure and a pair of parallel conductors, said first ground plane being an enclosure supporting said parallel conductors therein;

a second transmission line section comprising a second ground plane enclosure supporting said first enclosure therein and being oriented with respect to the latter for supporting electromagnetic fields therebetween;

a first contact electrically connecting and shortcircuiting both of said parallel conductors to said first ground plane enclosure, said first transmission line section comprising the short-circuited lengths of said parallel conductors and said first ground plane enclosure;

means producing a short circuit on said second transmission line section for defining the electrical length thereof; and

means for connecting impedances to be matched to each of said line sections.

7. An impedance matching network comprising a first transmission line section supporting a combination of odd and even modes and comprising lengths of a first ground plane enclosure and a pair of parallel conductors;

a second transmission line section comprising a second ground plane that is oriented with respect to said first ground plane for supportingelectromagnetic fields therebetween;

a first contact electrically connecting and shortcircuiting both of said parallel conductors to said first ground plane for defining the electrical length of said first line section, said first transmission line section comprising the short-circuited lengths of said parallel conductors and said first ground plane;

a second contact electrically connecting said first and second ground planes together for defining the electrical length of said second line section, said second transmission line section comprising the short-circuited lengths of said first and second ground planes; and

means for connecting impedances to be matched to each of said line sections;

said first ground plane being located between, spaced from, and parallel to said second ground plane and the plane defined-by said conductors.

8. Apparatus according to claim 2 wherein said fourth short circuiting conductor extends between said parallel conductors and connects the latter together over the lengths thereof between said third conductor and said wall.

9. Apparatus according to claim 4 wherein said first ground plane is an enclosure supporting said parallel conductors therein and said first short circuiting means comprises a movable wall in said enclosure, said wall being electrically connected to both of said conductors and to said enclosure and positioned between the connection points and adjacent one ends of said parallel conductors, said first transmission line section comprising the short circuited length of said parallel conductors between said wall and said connection points.

10. Apparatus according to claim 9 wherein said second short circuiting means comprises an electrically conductive trombone sliding structure extending over and electrically connected to the other ends of said parallel conductors, said second transmission line section comprising the short circuited length of said parallel conductors between said trombone structure and said connection points.

1 1. Apparatus according to claim 5 wherein said first short circuiting means comprises a first contact electrically connecting both of said parallel conductors and said first ground plane together, said first transmission line section comprising the short circuited lengths of said parallel conductors and said first ground plane.

12. Apparatus according to claim 11 wherein said second short circuiting means comprises a second contact electrically connecting said first and second ground planes together, said second transmission line section comprising the short circuited lengths of said first and second ground planes.

13. Apparatus according to claim 6 wherein said short circuiting means comprises a second contact electrically connecting said first and second enclosures, said second line section comprising the short circuited lengths of said first and second enclosures.

14. Apparatus according to claim 13 wherein said first and second contacts are movable in said enclosures for varying the electrical lengths of the associated line sections and matching impedances connected thereto.

15. Apparatus according to claim 7 wherein a first impedance is connected between one of said parallel conductors and said first ground plane and a second impedance to be matched to the first impedance is connected between the other one of said parallel conductors and said second ground plane.

16. Apparatus according to claim 15 wherein said line sections are stripline circuits, said first ground plane extending around said conductors over the lengths thereof, said second ground plane also extending around said first ground plane over the length thereof.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,745,433 Dated July 10, 1973 Inventoflsy Robert G. Rogers It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 10, "Y should read Y column 2, line 18, "Y should read Y Column 5, equation (3) should read 1 1 11 1 J'[ 3( J' l j J/C j( 1 3 LJJ] column 5, equation (4) should read I 2 2 B1 GiB GLB iG LcB BL) (G GL) 1/(GL G and column 5, equation (5 should read t 3 l i L [.(Bi 13 1 GL)2]/(GL il-"- Column 8, line 35, the numeral "95" should read 93 .7

Signed and sealed this 20th day of August 197A.

(SEAL) Atte'st: r

McCOY M. GIBSON, JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents FORM PO-1OSO(10-69) USCQMM-DC 60376 9" u.l. covnnulur nnmue omcl ll" O'JN-IJI

Claims

1. Transmission line apparatus geometrically configured for supporting both odd and even mode electromagnetic waves for matching a first impedance to a second impedance, comprising first and second parallel conductors; a conductive ground plane enclosure supporting said parallel conductors therein; said conductors being oriented in said enclosure with respect thereto for supporting odd and even moDes therebetween, said parallel conductors having one ends thereof for connection to associated impedances to be matched; means for connecting the first and second impedances between said adjacent one ends of said first and second conductors, respectively, and said enclosure; a movable wall of said enclosure electrically short-circuiting said parallel conductors together and to said enclosure for providing a first short circuit; the lengths of parallel conductors between the one ends thereof and said wall defining a length of transmission line of adjustable length primarily supporting over its length only even modes; a third conductor electrically movably contacting both of said parallel conductors at second adjacent points thereon between said one ends thereof and said wall for providing a second short circuit, the length of parallel conductors between the one ends thereof and said third conductor defining a length of transmission line of adjustable length supporting both even and odd modes; and a rod extending slidably through said wall and between said parallel conductors and being connected to said third conductor for moving the position of the latter and the second short circuit provided thereby along said parallel conductors.

2. Transmission line apparatus geometrically configured for supporting both odd and even mode electromagnetic waves for matching a first impedance to a second impedance, comprising first and second parallel conductors; a conductive ground plane enclosure supporting said parallel conductors therein; said conductors being oriented in said enclosure with respect thereto for supporting odd and even modes therebetween, said parallel conductors having one ends thereof for connection to associated impedances to be matched; means for connecting the first and second impedances between said adjacent one ends of said first and second conductors, respectively, and said enclosure; a movable wall of said enclosure electrically short-circuiting said parallel conductors together and to said enclosure for providing a first short circuit; the lengths of parallel conductors between the one ends thereof and said wall defining a length of transmission line of adjustable length primarily supporting over its length only even modes; a third conductor electrically movably contacting both of said parallel conductors at second adjacent points thereon between said one ends thereof and said wall for providing a second short circuit, the length of parallel conductors between the one ends thereof and said third conductor defining a length of transmission line of adjustable length supporting both even and odd modes; and a fourth conductor electrically connecting and short-circuiting said parallel conductors together and being located approximately intermediate said wall and said third conductor.

3. Transmission line apparatus geometrically configured for supporting both odd and even mode electromagnetic waves for matching a first impedance to a second impedance, comprising first and second parallel conductors that are rods having unequal diameters; a conductive ground plane enclosure supporting said parallel conductor rods therein; said conductor rods being oriented with respect to said ground plane enclosure for supporting odd and even modes therebetween, said parallel conductor rods having first adjacent points thereon for connection to the associated impedances to be matched; first means electrically short-circuiting said parallel conductor rods together; and second means electrically short-circuiting said parallel conductor rods together and to said ground plane; the positions of said first and second short circuits provided by said first and second short-circuiting means being independently movable along said parallel conductor rods for tuning the apparatus.

4. An impedance matching network comprising a first transmission line section supporting a combination of odd and even mOdes and comprising lengths of a first ground plane and a pair of parallel conductors; a second transmission line section; first and second means producing short circuits on said first and second transmission line sections, respectively, for defining the electrical lengths of the associated line sections; and means for connecting impedances to be matched to each of said line sections at adjacent points that are spaced away from the ends of associated parallel conductors thereof.

5. An impedance matching network comprising a first transmission line section supporting a combination of odd and even modes and comprising lengths of a first ground plane and a pair of parallel conductors; a second transmission line section comprising a second ground plane oriented with respect to said first ground plane for supporting electromagnetic fields therebetween; first and second means producing short circuits on said first and second transmission line sections, respectively, for defining the electrical length of the associated line sections; and means for connecting impedances to be matched to each of said line sections.

6. An impedance matching network comprising a first transmission line section supporting a combination of odd and even modes and comprising lengths of a first ground plane enclosure and a pair of parallel conductors, said first ground plane being an enclosure supporting said parallel conductors therein; a second transmission line section comprising a second ground plane enclosure supporting said first enclosure therein and being oriented with respect to the latter for supporting electromagnetic fields therebetween; a first contact electrically connecting and short-circuiting both of said parallel conductors to said first ground plane enclosure, said first transmission line section comprising the short-circuited lengths of said parallel conductors and said first ground plane enclosure; means producing a short circuit on said second transmission line section for defining the electrical length thereof; and means for connecting impedances to be matched to each of said line sections.

7. An impedance matching network comprising a first transmission line section supporting a combination of odd and even modes and comprising lengths of a first ground plane enclosure and a pair of parallel conductors; a second transmission line section comprising a second ground plane that is oriented with respect to said first ground plane for supporting electromagnetic fields therebetween; a first contact electrically connecting and short-circuiting both of said parallel conductors to said first ground plane for defining the electrical length of said first line section, said first transmission line section comprising the short-circuited lengths of said parallel conductors and said first ground plane; a second contact electrically connecting said first and second ground planes together for defining the electrical length of said second line section, said second transmission line section comprising the short-circuited lengths of said first and second ground planes; and means for connecting impedances to be matched to each of said line sections; said first ground plane being located between, spaced from, and parallel to said second ground plane and the plane defined by said conductors.

11. Apparatus according to claim 5 wherein said first short circuiting means comprises a first contact electrically connecting both of said parallel conductors and said first ground plane together, said first transmission line section comprising the short circuited lengths of said parallel conductors and said first ground plane.