US3904995A - Ultra high frequency impedance adjustment means - Google Patents

Abstract

An improved cavity type ultra high frequency impedance matching means in which tuning is accomplished by providing the inner and outer conductors of a feed line having a relatively small diameter as compared to an associated tuning cavity means and in which the shorting disc comprises radially moveable, spring biased wedge means for releasably locking the shorting disc in desired adjusted position and release operating means connected to release the wedged portions of the disc and sliding the disc to a new adjusted position for impedance adjustment.

Description

United States Patent Phillips [451 Sept. 9, 1975 [54] ULTRA HIGH FREQUENCY IMPEDANCE 2,796,587 6/1957 Phillips 333/33 ADJUSTMENT MEANS 2,901,712 8/1959 Hogg 333/33 [75] Inventor: Edwin N. Phillips, Winter Park, Fla.

[73] Assignee: The United States of America as represented by the Secretary of the Navy, Washington, DC. 22 Filed: July 10, 1974 [2]] App]. No: 487,115

[52] US. Cl 333/33; 333/97 R; 331/96; 330/31; 330/56 [51] Int. Cl.*.... HOIP 5/00; HOlP 1/28; HO3H 7/38 [58] Field of Search 330/56, 31; 315/3953; 333/33, 97 R; 331/96, 101, 103

[56] References Cited UNITED STATES PATENTS 2,203,806 6/1940 Wolf 333/97 R 2,763,842 9/1956 Olive 333/33 A /0 Z V CONTROL GRID :3 z x 2 0 CA 114005 2 /7 N 30 I5 SHORT CAVI TY CIRCUITED J T 26 MAIN SHOR TING PIS TON FEED Primary ExaminerPaul L. Gensler Attorney, Agent, or Firm-Richard S. Sciascia; John W. Pease ABSTRACT 6 Claims, 11 Drawing Figures OUTER CONDUCTOR 62 CAPT/VA TED TENS/0N SPRING SPLIT ANNULUS ACTUATOR BASE l2 CONTROL DISCS PATENTED SEP 9 I975 SHEET 1 BF 4 kmQIm PATENTEDSEP 191s snwau g OUTER CONDUCTOR INNER CONDUCTOR OUTER C'ONDUC TOR ANNULAR 64 SHOE SLIDING WEDGE SLIDING WEDGE PISTON CAPT/VA TED TENS/0N SPRING SPLIT ANNULUS b ACTUATOR RODS ACTUATOR BASE I2 CONTROL DISCS FIG.2'A-

- SLIDING WEDGE CASCADE UPPER SLIDING WEDGE 78 COMPRESSION SPRING 72 Ly LOWER SLIDING WEDGE FIG. 3

J z ACTUATOR RODS OUTSIDE BASE- IZ CONTROL DISKS FINGER STRIP TOP 8 BOTTOM I SLIDING- WEDGE A SSEMBL Y WITH FINGERED- BARREL COMPRESSION SPRING LOWER SLIDE WEDGE FIG. 4

UPPER 62 WEDGE 60 TRAIN l I 96 I I SLIDING- WEDGE-CASCADE I ALONG OUTER CONDUCTOR I I02 X- INNER ANNULAR b D SHOE LOWER WEDGE TRAIN W FIG. 5

PATENTED 1 75 suwuuig 62 OUTER CONDUCTOR INNER CONDUC TOR E Ma TD SM aw U56 U83 004 MP6 CP- p m RMB wmw SUD R IE N W E R Mi h PE 6 INNER OUTER UPPER WEDGE RACE 6 m m A F m D E w w M V! R R W T E E R S W W E R R V Du E D D m M A 0 0 W M w M 0 3 RE M M a 6 T L M N6 Y Y L 0W AP T T Y L 5 5 T ,A J I S 1 w f 6 W STYL/ZED PLA TE ULTRA HIGH FREQUENCY IMPEDANCE ADJUSTMENT MEANS BACKGROUND OF THE INVENTION The invention relates to the field of coupling networks and in particular to those having long line elements where a function of adjustable match or mismatch is required.

In impedance matching means wherein a slidable disc member is employed for the purpose of adjusting impedance match such units have been found unsatisfactory in application to a small bore cable employing wire or filamentary type inner conductors. It has been found impossible to construct a shorting disc which can be made adjustable and which will provide reliable results in maintaining satisfactory electrical contact. With other than wire (or filamentary type) inner conductors, a variety of contacting means are known to have been successfully employed and have included finger strips having a plurality of fingers to abut the cylinder wall from a short-circuiting disc edge; coil springs which are preformed and then cocked in an annular slot to give a multiplicity of contacting points; and similar devices. However, none of these can be applied successfully to the wire-like small diameter of the inner conductor of an air-cored coaxial line of small diameter.

SUMMARY OF THE INVENTION To provide for the deficiencies noted above the subject invention provides an improved cavity type ultra high frequency impedance adjustment means in which the short-circuiting piston is in the form of an arrangement of a chuck having a plurality of wedges whose gripping surfaces can be engaged normally under spring pressure but which can be released from outside the structure so that movement of the composite piston along the line axis can be effected with the fingers retracted. Operating means connected to act upon the spring means to release the wedge bias on the disc elements are provided so that the disc can be moved to a new position for impedance matching adjustment.

DESCRIPTION OF THE DRAWING FIG. 1 is an elevational view of an input circuit of a UHF (ultra high frequency) amplifier used as an impedance matching device applied to a vacuum tube amplifier and incorporating a shorting disc incorporating the invention;

FIGS. 1A, 1B and 1C are a schematic electrical diagram and Smith Chart Maps used to explain the matching function of the apparatus of FIG. 1;

FIG. 1D shows in schematic a modification of the apparatus of FIG. 1 to utilize a transistor instead of a tube for amplification;

FIGS. 2 through 6 are cross sectional views of several preferred embodiments of the disc and actuator portions of the impedance adjustment means of FIG. 1;

FIG. 2A is a plan view of the segmented disc arrangement of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the field of oscillators and amplifiers used at very high frequencies (in particular the region lying roughly between 100 and 1000 megacycles per second), the housing of the active part of the system is commonly called a cavity. Such structures are actually devices for providing the appropriate impedance transformations at the input and output ends of the assembly. The term cavity is used in this sense in the writings hereinafter.

Referring to FIG. 1, the arrangement of concentric tubes 12 and 14 represent the input circuit of a UHF amplifier indicated generally at 10 which has a tunable feed transmission line circuit generally indicated at 15 and which includes an incoming section 17 and a tuning section 19. Each of the sections 17 and 19 comprise coaxial conductors having outer conductor 16 enclosing inner conductor 18. A disc shorting means 20 is provided in section 19. The load on the impedance matching circuit, including the elements mentioned above, can be the input part of a vacuum tube represented in FIG. 1 by the control grid 22 and cathode 24. The interspace between the control grid 22 and the cathode 24 presents an impedance which requires matching to the incoming coaxial transmission line 15. An arrow head 26 shows the direction of flow of the incoming incident power. While a vacuum tube input is shown in FIG. 1 as the load for the impedance matching (adjusting) means including the coaxial input line 15 and its associated adjustable shorting disc 20, it could equally well be the input circuit of a UHF transistor type amplifier (shown in FIG. 1D) between its base and emitter elements, and it could equally well be the input circuit of a UHF travelling wave tube or other amplifying device (not shown).

In FIG. 1 the outer conductor 16 of the incoming section 17 of the feed transmission line 15 is fastened to the inner wall of outer tube 14 all the way along until the outer conductor 16 stops at its meeting with the control grid 22. The inner conductor 18 of the same incoming line 15 continues across the physical gap between the control grid 22 and cathode 24 and it there continues as the inner conductor (still referred to as 18) of the tuning section 19 with its outer conductor maintaining the identification 16. The outer conductor 16 of tuning section 19 is conductively fastened to the outer wall of tube 12. Solder or other suitable means can be used to conductively fasten the respective conductors l6 and tubes 12 and 14. The inner conductor 18 is stopped (electrically) by the small short circuiting disc 20, although it may physically continue through the center of the disc 20, as indicated, for such purpose as constructional anchoring.

In FIG. 1 the incoming UHF power flows into the feed T/L (feed transmission line) 15 as indicated by the arrow 26. It is at the gap in the outer conductors of the two small'bore coaxial line sections 17-19 that interest centers. The mismatched load lies in parallel with the portion of the main cavity between the grid-cathode gap and the main shorting piston 28 shown in the diagram. This axial length indicated by the bracket 30 is generally shorter than a quarter wavelength so that it shows an inductive reactance, 32, (FIG. 1A) at the gap, this being in shunt with the parallel resistance 34 and capacitance 36 presented by the tubes input circuit. This reactance is shown on the assembly diagram as X /Z 2 being the cavity surge impedance. Hence, at any one frequency, it can be represented as a coil in shunt with the mismatched load Z All of these impedances are ultimately normalized against the surge impe' dance Z of the incoming Feed-T/L 15. Because of the gap in the outer conductor of the incoming Feed-T/L 15, the paralleled combination of the cavity reactance and the mismatched load impedance is in series with the incoming Feed-T/L through the small-bore coaxial cable section 19 which extends down along the inner conductor 12 outer wall, this being called a shortcircuited T/L. Only when the combined currents from the cavity reactor and the mismatched load flow down the inner surface of this line section 19 outer conductor 16, across the small short-circuiting disc 20, and up this lines inner conductor 18, can they then flow out through the inner conductor 18 of the Feed-T/L 15, section 17, and complete the circuit. Hence, the input reactance of this captive small-bore short-circuited T/ L section 19 must be in series with the paralleled load and reactor; accordingly, it is shown as a series coil 38 at the head end of the circuit (see FIG. 1A). When, as is usual, this short-circuited T/L section 19 is less than a quarter wavelength in axial length, it can be represented as an inductor at its input port. The normalization to the 2., base through the separate multipliers is shown on the schematic FIG. 1A.

The impedance range over which this ell-network will match is shown diagrammatically in FIG. 1B and 1C. The extremes are shown as limit arcs and limit points, and these form the area shown in FIG. 18. Fortunately, most UHF matching in these circumstances involves the same paralleled combination of resistance and capacitance mentioned in the foregoing (i.e., the input impedance of a UHF tube or transistor), so that this arrangement of inductors will match, as the Smith Chart map indicates in FIGS. 18 and 1C.

FIG. 1D is a partial redrawing of FIG. 1 showing how the invention would be applied to a transistor in place of a tube amplifier. Thus, the outer conductor 16 of line section 17 is connected to the base 31 of a transistor 33 and the outer conductor 16 of line section 19 is connected via plate 35 to the emitter 37 of the transis tor 33. This apparatus with the transistor 33 operates in the same manner as described for the tube amplifier arrangement of FIG. 1.

In order to carry out the adjustment of the frequency impedance adjustment means of FIGS. 1 and 1D it is necessary that the shorting disc 20, (also commonly referred to as a piston) be applicable for operation between the inner and outer conductors of a wire-like aircored coaxial line of small diameter and that it be man ufacturable, externally adjustable, and reliable in contact with both the inner and outer conductors.

In accordance with a further aspect of the invention the short circuiting piston is that of a chuck whose grasping surfaces can be engaged normally under spring pressure but which can be released from outside the structure so that movement of the composite shorting piston along the line axis can be effected with the fingers retracted. Several preferred embodiments of the short circuiting piston and operating means are shown in FIGS. 2 through 6.

In one embodiment, as shown in FIG. 2, a spring biased wedge meanas is provided which comprises an annulus, generally indicted at 40, split to form inclined adjacent surfaces 42, 44 and segmented to form combinations of inner annulus wedge segments 46 and outer annulus wedge segments 48. Each pair of associated inner and outer wedges 46, 48 are reacessed as at 50, 52 to receive a captive tension spring 54. Extending through each spring coil and extending to the dead outside space of the cavity are provided actuator rods 56 which connect to outside base plate control discs 58.

FIG. 2A shows a plan view of the segmented discs of FIG. 2. When not compressed for sliding the wedges, the spring 54 holds its associated pair of inner and outer wedges securely tight and in good electrical contact with the respective inner conductor 60 and outer conductor 62. Pushing the outside base control discs 58, 59 together urges the wedges 46, 48 away from interface with the inner and outer conductors so that the whole assembly can be moved axially to a new adjusted location. Disc 59 is connected by rod 57 to the lower wedge 48 as indicated.

In another embodiment of the spring biased wedge means, as shown in FIG. 3, an annulus is segmented to form outer shoes 64 for engaging the outer conductor 62 and each shoe is recessed to form a V-shaped inner surface (or any suitable shape presenting inclined wedging surfaces) forming upper and lower wedging surfaces 66 and 68. Pairs of upper and lower inner shoes 70, 72 are formed with cam surfaces 74, 76 mating respectively with said upper and lower annulus wedging surfaces 66, 68 for sliding thereon. Compression spring means 78 is held captive in recesses 80, 82 formed in the wedges 70, 72. Outside base control discs 84, 86 are connected respectively to the annulus 64 and spring 78 by rods 88, 90 and must be pulled apart to enable release and ensuing adjustment of the shoes and wedges axially along the conductors 60 and 62. It is contemplated further that, as shown in FIG. 4, finger strips 92 and 94 may be added to the annular shoes 64 to improve electrical contact and to maintain electrical contact when the outer conductor 62 is out of round. The remainder of the elements are as in FIG. 3.

In FIG. 5 is shown another variant following the invention in which an inner segmented annulus holds captive in a V-shaped recess 102 a train of outer upper and lower shoes 96 and 98. The spring biasing and rod arrangement remains the same.

This leads to the ultimate in preferred embodiment of the spring biased wedge means portion of the invention (FIG. 6) wherein an annulus 104 is formed with reversed V-shaped recesses 106 and 108 on the inner and outer peripheries to hold captive a train of inner upper and inner lower shoes 110, 112 and outer upper and outer lower shoes 114, 116. Captive compression springs 118 and 120 are held captive in recessed portions indicated of the associated pairs of shoes and the two sets of shoes are released by rods 122 and 124 being moved downwardly by plate 128 and rod 126 being moved upwardly by plate 130. It is to be noted that in the case of the arrangement of FIG. 6 the annulus 104 (annular race) is solid, rather than being composed of a train of segments as indicated in FIG. 38, so that the annulus 104 can serve as the mechanical base for the multiple actuator rods.

It will be understood that various changes in the details and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.

What is claimed is:

1. An improved cavity type ultra high frequency impedance adjustment means comprising:

wave guide means having outer and inner concentric walls defining a tuning cavity therebetween,

a coaxial feed transmission line having inner and outer conductors and having a relatively small cross-section in comparison to said wave guide means,

said coaxial feed line terminated within said wave guide means to form thereof an incoming section and a tuning section with said incoming section outer conductor connected to said outer wave guide means wall and said tuning section outer conductor connected to said inner wave guide means wall,

a shorting disc slidably connected between said inner and outer conductors of said tuning section of said feed line,

said shorting dis'c comprising radially moveable spring-biased wedge means for locking said shorting disc in fixed adjusted seated position, and

operating means connected to said spring to release said wedge bias when said disc is to be moved for impedance adjustment.

2. Apparatus according to claim 1 wherein said spring biased wedge means includes an annulus split to form inclined adjacent wedging surfaces and segmented to form combinations of inner and outer annulus wedge segments,

a tension spring for each combination of wedging segments,

said segments being recessed to hold said tension spring in captive position to bias said wedge segments in wedging position respectively against said outer and inner conductors of said feed line.

3. Apparatus according to claim 1 wherein said spring biasing wedge means includes an annulus segmented to form outer shoes, each shoe being recessed to form a V-shaped inner surface forming upper and lower wedging surfaces,

pairs of upper and lower inner shoes having cam surfaces mating respectively with said upper and lower annulus wedging surfaces for sliding thereon,

compression spring means,

said sliding wedges being recessed to hold said compression spring captive between said sliding upper and lower inner shoes.

4. Apparatus according to claim 3 including spring-biased finger tips provided on said outer shoes to improve extent and reliability of satisfactory contact with said outer conductor.

5. Apparatus according to claim 1 wherein said spring-biased wedge means includes an annulus segmented to form inner shoes, each shoe being recessed to form a V-shaped outer surface forming upper and lower wedging surfaces,

pairs of upper and lower outer shoes having cam surfaces mating respectively with said upper and lower annulus wedging surfaces for sliding thereon,

compression spring means,

said sliding wedges being recessed to hold said compression spring captive between said sliding upper and lower oute'r shoes.

6. Apparatus according to claim 1 wherein said spring biased wedge means includes an annulus having an outer and an inner peripheral V-shaped recess,

pairs of upper and lower inner shoes having cam sur faces mating with said inner peripheral V-shaped recess and pairs of upper and lower outer shoes having cam surfaces mating with said outer peripheral V-shaped recess, forming double opposed wedge trains are for contacting said inner conductor and are for contacting said outer conductor,

a compression spring means for each of said shoe pairs each pair of shoes being recessed to hold its associated compression spring captive.

[SEAL] UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION patent 3,'9.04 ,995' Dated September 9 1975 Edwin N. Phillips Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the Abstract, line 3, after "providing" and before "the" insert a shorting disc slidably connected between Signed and Scaled this Attest:

RUTH C. MASON C. IAISIIALL DANN Arresting Office! Commission" of File. and Trademarks thirtieth Day of December 1975

Claims (6)

1. An improved cavity type ultra high frequency impedance adjustment means comprising: wave guide means having outer and inner concentric walls defining a tuning cavity therebetween, a coaxial feed transmission line having inner and outer conductors and having a relatively small cross-section in comparison to said wave guide means, said coaxial feed line terminated within said wave guide means to form thereof an incoming section and a tuning section with said incoming section outer conductor connected to said outer wave guide means wall and said tuning section outer conductor connected to said inner wave guide means wall, a shorting disc slidably connected between said inner and outer conductors of said tuning section of said feed line, said shorting disc comprising radially moveable spring-biased wedge means for locking said shorting disc in fixed adjusted seated position, and operating means connected to said spring to release said wedge bias when said disc is to be moved for impedance adjustment.

2. Apparatus according to claim 1 wherein said spring biased wedge means includes an annulus split to form inclined adjacent wedging surfaces and segmented to form combinations of inner and outer annulus wedge segments, a tension spring for each combination of wedging segments, said segments being recessed to hold said tension spring in captive position to bias said wedge segments in wedging position respectivelY against said outer and inner conductors of said feed line.

3. Apparatus according to claim 1 wherein said spring biasing wedge means includes an annulus segmented to form outer shoes, each shoe being recessed to form a V-shaped inner surface forming upper and lower wedging surfaces, pairs of upper and lower inner shoes having cam surfaces mating respectively with said upper and lower annulus wedging surfaces for sliding thereon, compression spring means, said sliding wedges being recessed to hold said compression spring captive between said sliding upper and lower inner shoes.

4. Apparatus according to claim 3 including spring-biased finger tips provided on said outer shoes to improve extent and reliability of satisfactory contact with said outer conductor.

5. Apparatus according to claim 1 wherein said spring-biased wedge means includes an annulus segmented to form inner shoes, each shoe being recessed to form a V-shaped outer surface forming upper and lower wedging surfaces, pairs of upper and lower outer shoes having cam surfaces mating respectively with said upper and lower annulus wedging surfaces for sliding thereon, compression spring means, said sliding wedges being recessed to hold said compression spring captive between said sliding upper and lower outer shoes.

6. Apparatus according to claim 1 wherein said spring biased wedge means includes an annulus having an outer and an inner peripheral V-shaped recess, pairs of upper and lower inner shoes having cam surfaces mating with said inner peripheral V-shaped recess and pairs of upper and lower outer shoes having cam surfaces mating with said outer peripheral V-shaped recess, forming double opposed wedge trains are for contacting said inner conductor and are for contacting said outer conductor, a compression spring means for each of said shoe pairs each pair of shoes being recessed to hold its associated compression spring captive.

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