United States Patent (19) 11 4,039,974 Clark et al. 45 Aug. 2, 1977

2,968,772 1/1961 Thomas, Jr...... 333/73 C (54) COAXAL FREQUENCY SWITCH 3,132,311 5/1964 Wozniak ...... 333/97 RX HAVING INTEGRAL FILTER 3,309,632 3/1967 Trudeau ...... 333/97 RX (75) Inventors: Neil V. Clark, Sunnyvale; Homer G. 3,530,504 9/1970 Konishi ...... 333/7 RX Holzgrafe, Santa Barbara, both of 3,969,690 7/1976 Hansen et al...... 333/7 R Calif. Primary Examiner-Paul L. Gensler 73) Assignee: Raytheon Company, Lexington, Attorney, Agent, or Firm-Richard M. Sharkansky; Mass. Philip J. McFarland; Joseph D. Pannone 21 Appl. No.: 610,367 57 ABSTRACT A coaxial transmission line switch is disclosed, such 22 Filed: Sept. 4, 1975 switch having a rotatable coupling element reactively 51 nt. C.2 ..... o Po pro-do so was eo poa e o so puboea no ope H01P 1/12 coupled between an input coaxial transmission line and 52) U.S. C...... 8 0 0 w v 4, 88 a a 48 8 oo is 333/7 R; 333/73 C a selected one of a plurality of output coaxial transmis (58) Field of Search ...... 333/7 R, 7 D, 24 C, sion lines. The rotatable conducting element, the input 333/97 S, 73 C coaxial transmission line, and the plurality of output coaxial transmission lines have connected radio (56) References Cited frequency stubs thereby forming a filter integrally with U.S. PATENT DOCUMENTS the coaxial transmission line switch. 2,426, 186 8/1947 Dow ...... 333/7 RX 2,452,202 10/1948 Lindenblad...... 333/7 RX 5 Claims, 4 Drawing Figures

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SELECTED ONE NPUT L- L-2 L-3 OF THE OUTPUT EgRT. PORTS, 28, 3O 4,039,974 1. 2 mission line and the plurality of output coaxial transmis COAXAL SWITCH HAVING sion lines also have shunt connected radio frequency INTEGRAL FILTER stubs, thereby forming a filter integrally with the coax ial transmission line switch. BACKGROUND OF THE INVENTION This invention relates generally to radio frequency BRIEF DESCRIPTION OF THE DRAWINGS switches and more particularly to coaxial transmission The above and other objects of the invention will line switches. become better understood by reference to the following As is known in the art, one type of coaxial transnis description taken together in conjunction with the ac sion line switch includes a rotatable coupling element in 10 companying drawings, in which: contact with the center conductor of an input coaxial FIG. 1 is an exploded isometric drawing, partially transmission line and adapted for contacting the center broken away and partially cross-sectional, showing the conductor of a selected one of a plurality of output coaxial transmission line switch according to our inven coaxial transmission lines. Such switch is described in tion; " Transmission Circuits' edited by George 15 FIG. 2 is a diagrammatic drawing of the coaxial trans L. Ragan, published and distributed by Boston Techni mission line switch shown in FIG. 1, such drawing cal Publishers, Inc., 5 Bryant road, Lexington, Mass. being useful in understanding features of such switch; 02:173, 1974 edition. While such type of coaxial trans FIG. 3 is a schematic diagram useful in understanding mission line switch has been found adequate in many features of the coaxial transmission line switch; and, applications, the power handling capability and life of 20 FIG. 4 is a cross-sectional view of the coaxial trans such type of coaxial transmission line switch is limited mission line switch shown in FIG. 1, such cross-section because of the possibility of breakdown result being taken along line 4-4 in such FIG. 1. ing from metal shavings from the contacting center DESCRIPTION OF THE PREFERRED conductors being present in the region of strong radio EMBODIMENT frequency fields. 25 It is also known in the art that it is sometimes desirable Referring now to FIG. 1, a coaxial transmission line to form filters from sections of coaxial transmission switch 10 is shown, and a diagrammatical sketch thereof lines. Such filters may be formed because, at radio fre is shown in FIG. 2. Such switch 10 includes a housing quencies, a may be realized in a coaxial trans 12 made of any suitable electrical conductive material, mission line by a series gap in the center conductor of 30 here aluminum. Such housing 12 forms the outer con such transmission line and an may be realized ductor of three coaxial transmission lines 14, 16, 18, the by a proper length of shorted transmission line, (i.e. a inner center conductors of such coaxial transmission radio frequency ) connected in shunt to the center lines being conductors 20, 22, 24 respectively, here conductor of the coaxial transmission line. further, such hollow aluminum tubes. It is here noted that the hous "' and "' may be arranged to en 35 ing 12 is in two sections which are bolted together by able the filter formed from such coaxial transmission conventional bolts, not shown. One end of the coaxial line to provide for matching between the impedance of transmission lines 14, 16, 18 forms input port 26 and the source driving such transmission line and the imped output ports 28, 30 respectively and the other end of ance of the load coupled to the output of such transmis transmission lines 14, 16, 18 is disposed in the common sion line. It would sometimes be desirable to incorpo 40 region 31 (such region not being numbered in FIG. 1 rate such a filter integrally with a coaxial transmission but being numbered in FIG. 2). Disposed in such com line switch, however, the coaxial transmission line mon region 31 is a switching arm 32, here also made of switch described above does not include such an inte aluminum, one end of which is capacitively coupled to grally formed filter. the center conductor 20 of the coaxial transmission line 45 14 through a dielectric disc 34. The switching arm 32 is SUMMARY OF THE INVENTION adapted to rotate about axis 36 here by a conventional It is therefore an object of this invention to provide an motor drive unit 38 so that the second end of such arm improved coaxial transmission line switch. 32 may be capacitively coupled to a selected one of the It is another object of this invention to provide an center conductors 22, 24 through a dielectric ring 40. In improved coaxial transmission line switch having a 50 particular the shaft 42 of the motor 38 is mechanically rotatable coupling element coupled to an input coaxial coupled in any conventional manner to a radio fre transmission line and a selected one of a plurality of quency stub 44 formed integrally with the arm 32. Also output coaxial transmission lines, such rotatable cou formed integrally with such arm 32 is a conductive pling element not being required to be in contact with cu-shaped element 46 which is rotatable within the the center conductors of such selected one of the plural 55 housing 12. It is noted that the cup-shaped conductive ity of output coaxial transmission lines and the center element 46 is cylindrically shaped and has an electrical conductor of the input coaxial transmission line. length sufficient to effectuate a radio frequency short It is another object of this invention to provide an circuit between such element 46 and the housing 12. improved coaxial transmission line switch having a Such cup-shaped conductive element 46 has an electri filter integrally formed therewith. 60 cal length A/4 where N is the nominal operating These and other objects of the invention are attained length of the switch 10. Such conductive element 46 generally by providing a coaxial transmission line serves to inhibit radio frequency energy passing switch having a rotatable coupling element reactively through such switch 10 from coupling into the drive coupled between an input coaxial transmission line and unit 38 and electrical cables (not shown) coupled to a selected one of a plurality of output coaxial transmis 65 such drive unit. Such conductive element 46 then pro sion lines. In a preferred embodiment of the invention vides a short circuit radio frequency stub in shunt to the such rotatable conducting element has a shunt con switching arm 32. Dielectric discs 48, 50, 52 are pro nected radio frequency stub and the input coaxial trans vided to support one end of each one of the center 4,039,974 3 4. conductors 20, 22, 24 respectively within the housing preferred embodiment but rather should be limited only 12. The other end of the center conductors 22, 24 is by the spirit and scope of the appended claims. supported, in part, by a channel formed in the dielectric What is claimed is: ring 40. Support for the center conductor 20 is in part 1. A coaxial transmission line switch comprising: provided by a recess formed in dielectric disc 34 as 5 a. a housing for such switch; b. an input coaxial transmission line; shown. Radio frequency stubs 54, 56, 58 are formed c. a plurality of output coaxial transmission lines, such integrally with the center conductors 20, 22, 24 and housing providing outer conductors for the input provide short circuit radio frequency stubs in shunt to coaxial transmission line and the plurality of output the center conductors, 20, 22, 24, as indicated. Such 10 coaxial transmission lines; radio frequency stubs 54, 56, 58 are fastened to the d. a radio frequency filter, comprising: housing 12 by conventional screws 62, 64, 66 respec a plurality of radio frequency stubs having first ends tively as indicated in FIG. 1. As shown more clearly in thereof connected to center conductors of the input FIG. 4, with regard to screw 64 and stub 56, such stubs coaxial transmission line and the plurality of output 54, 56, 58 are drilled and tapped. Screws 62, 64, 66 are 15 coaxial transmission lines; inserted through housing 12 and then screwed into the and a rotatable coupling element, disposed in the drilled and tapped holes thereby ensuring electrical housing, reactively coupled between the input co connection between the center conductors 20, 22, 24 . axial transmission line and a selected one of a plural and the housing 12. The radio frequency stubs 54, 56, ity of output coaxial transmission lines, such filter 58, fastened to the housing 12 as described, provide being formed integrally with the switch to filter additional support for the center conductors 20, 22, 24 signals fed to the input coaxial transmission line and and also provide thermal conductive paths for extract coupled to the selected one of the plurality of out ing heat from such center conductors. put coaxial transmission lines. Referring now to FIG. 3, an equivalent circuit of the 2. The switch recited in claim 1 wherein the plurality 25 of stubs have second ends connected to the housing to radio frequency switch 10 is shown. In such circuit: provide at least partial support of the inner conductors ratio frequency stub 54 forms an inductor L1; center connected thereto within the housing. conductor 20, dielectric disc 34 and arm 32 form a ca 3. The switch recited in claim 2 wherein the plurality pacitor Cl; radio frequency stub 44 forms the inductor. of stubs are arranged to provide a heat conduit between L2; arm 32, ring 40 and the selected one of the center 30 the center conductors and the housing. conductors 22, 24 form the capacitor C.; and, the one of 4. The switch recited in claim 3 wherein the filter the stubs 56, 58 of the selected center conductor forms formed by the filter means is a Tchebychef filter. the inductor L3. The equivalent circuit shown in FIG.3 5. The switch recited in claim 4 including a radio is that of a Tchebychef filter. frequency stub rotatably mounted within the housing Having described a preferred embodiment of this 35 and connected to the rotatable coupling element, such invention, it is now evident that other embodiments rotatable stub being electrically short circuited to the incorporating its concepts may be used. It is felt, there housing. fore, that this invention should not be restricted to such a

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UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 4,039,974 Dated August 2, 1977 Inventor(s) Neill W. Clark and Homer G. Holzgrafe 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 54, delete 'cu-shaped' and insert therefor -- cup-shaped -- eigned and Sealed this Twenty-fifth Day of October 1977 SEAL

RUTH C. MASON LUTRELLE F. PARKER Attesting Officer Acting Commissioner of Patents and Trademarks