US3181086A

US3181086A - Electrical switch with the outer conductors of coaxial leads connected to spaced shield plates

Info

Publication number: US3181086A
Application number: US116358A
Authority: US
Inventors: Samuel R Mccutcheon; Chester N Winningstad
Original assignee: Tektronix Inc
Current assignee: Tektronix Inc
Priority date: 1961-06-12
Filing date: 1961-06-12
Publication date: 1965-04-27
Anticipated expiration: 1982-04-27
Also published as: GB955435A; NL269260A; DE1246060B

Description

April 27, 1965 s. R. M CUTCHEON ETAL 3, 8 ,086 ELECTRICAL SWITCH WITH THE OUTER CONDUCTORS OF COAXIAL LEADS CONNECTED TO SPACED SHIELD PLATES Filed June 12, 1961 Fig. 2

26 4a 1 I I 4o 52 o i F lg. 3 2s Buckhorn, Cheafham 8 Blore ATTORNEYS United States Patent O" 3,181,086 ELECTREQAL SWITQH WITH THE QUEER (JQN- DUCTQRS F COAXIAL LEADS CQNNECTED TO SPACED SHEELD PLATES Samuel R. MeCutcheon, Aloha, and Chester N. Winningstad, Portland, Greg, assigziors to Telrtronix, Inc, ileaverton, Greg, a corporation of Qregon Filed June 12, 1961, Ser. No. 116,358 9 Claims. (Cl. 333-7) The present invention relates to an electrical switch and more particularly to a switch for changing the electrical connections between a plurality of transmission lines having similar characteristic impedances by mechanical movement of the switch contacts.

The electrical switch of the present invention is particularly useful for changing the electrical connections between a plurality of coaxial cable transmission lines having substantially the same characteristic impedance, such as those used to transmit high frequency or pulse signals. Conventional electrical switches are not suitable in such an environment because they produce a discontinuity in the transmission lines which causes undesirable reflection of signal voltages back along the input transmission line. In order to overcome the above problem it has previously been suggested to provide coaxial line switches which in effect operate by physically moving actual short sections of the coaxial cables from one position to another in order to provide continuous coaxial lines along alternate paths without reflection of signal voltages. However, this has not been an adequate solution to the problem because such switches are complicated, cumbersome and expensive.

The electrical switch of the present invention overcomes these disadvantages byv providing broadly a simple me chanical switch in which only the central conductors of coaxial transmission lines are switched in order to change connections between the transmission lines while the outer conductors of such lines are fixedly connected to common conductors. More specifically, the switch includes a pair of spaced metal shield plates providing common connection for the outer conductors of the transmission lines,

and a switch plate assembly for changing the connections between the inner conductors of such lines. The switch plate assembly includes a stationary stator plate and a a movable rotor plate properly positioned between the shield plates so that the shield plates provide in effect an equiv alent of the outer conductor of the coaxial cable transmission lines and the switch plate assembly provides an equivalent or" the signal carrying inner conductor of the transmission lines. This simple, inexpensive structure provides a switch in the form of a short section of transmission line having substantially the characteristic im pedance of the transmission lines connected thereto.

Therefore one object of the present invention is to provide an improved electrical switch which permits the changing of the electrical connections between a plurality of transmission lines without voltage reflections from said switch along said transmission lines.

Another object of the invention is to provide a simple electrical switch for changing the electrical connections between a plurality of transmission lines having similar characteristic impcdances so that such switch has a structure which is in effect a transmission line section having substantiallythe same characteristic impedance as said transmission lines.

A further object of the present invention is to provide a switch, to change the electrical connections between a plurality of coaxial cable transmission lines having similar characteristic impedances, in which a switch plate assembly adapted to be connected to the signal carrying con ductors of such lines and having a stationary stator memassists Patented Apr. 27, 1965 her and a moving rotor member is positioned in spaced relationship between a pair of spaced electrically conducting plates adapted to be connected to the outer conductors of such transmission lines so that the switch structure in effect forms a short section of transmission line having substantially the same characteristic impedance as the transmission lines connected thereto.

Additional objects and advantages of the present invention will become apparent upon referring to the following detailed description of a preferred embodiment of the present invention shown in the attached drawings of which:

FIG. 1 is a perspective View of an electrical switch made in accordance with the present invention;

FIG. 2 is a vertical section taken along the line 2-2 of FIG. 1 showing a portion of the switch and coaxial transmission line connections thereto; and

FIG. 3 is a section taken along the line 3-3 of FIG. 2 showing the switch plate and coaxial transmission lines connected thereto with connections to the outer conductors of such lines omitted.

An electrical switch made in accordance with the present invention is shown in FIG. 1 as including a circular metal support plate it which may have a conventional detent switch positioning means thereon including suitable mechanical stops. A suitable metal or nonmetallic shaft 12 is rotatably mounted in a hole through support plate ll so that its rotation is controlled by the detent switch positioning means on such support plate 10. Two fastening bolts 14 extend through holes in the support plate it). A metal spacer member 16 in the form of a cylindrical sleeve is mounted on each of these bolts 14 adjacent the support plate 1%). A first shieldplate 18 in the form of a circular, flat, metal plate having a pair of holes therein to accommodate the fastening bolts 14 and a clearance hole for the shaft 12, is mounted on such bolts against the spacer 16. A switch plate assembly 20 of insulating material provided with a pair of mounting holes for the fastening bolts 14 and a single hole for the shaft 12, is accurately spaced from the conducting plate 13 by a pair of insulating spacer sleeves 22 on the fastening bolts 1%. A second metal shield plate 24 having a circular shape is mounted in a similar manner on fastening bolts 14 and spaced from switch plate 20 by insulating spacer sleeves 26 similar to sleeves 22. Circular shield plates 18 and may have the same diameter and are provided with a concentric clearance hole through which the shaft 12 extends so that it is free to rotate without contacting the surface of such conductive plates. The switch assembly may be held on fastening bolts 14 and support plate lii by means of a nut and lock washer combination 3th on the threaded end or" such fastening bolts 14.

FIG. 2 shows coaxial cable transmission lines 32 connected to appropriate switch members including a pair of electrical connectors 34 extending between the grounded outer conductor 35 of each coaxial cable 32 and the

common shield plates

18 and 24. Switch plate assembly 29 includes two concentric

circular insulating members

36 and 38. The outer insulating member is a fixed annular stator plate 36 positioned on the fastening bolts 14 between

insulating spacer members

22 and 26, while the inner insulating member is a circular rotor plate 38 having a hole therein fitting a flattened portion of the shaft 12 so as to be rotated by the shaft. The stator plate 36 has a plurality of pairs of fixed metal spring contacts 40 attached in spaced relationship around the stator plate so as to extend radially thereof. These fixed contacts 40 are each in the form of a spring member having an end which extends outwardly from the outer periphery of the stator plate 36 for connection to the central conductor 44 of a coaxial cable, such as the cables 32, by soldering or the like. The rotor plate 38 is provided with a plurality of metal contact plates 46 in spaced insulated relationship which extend along the periphery of the rotor plate 38 and for a short distance over the inside edge of the stator plate 36 so that the outer surface of the contact.

plates 4-6 make mechanical contact with the spring ends of the fixed contacts 40 upon rotation of the shaft 12.

.It should be noted that the switch plate assembly 20 is symmetrical in that a pair of fixed contacts 46 and a pair of movable contact plates 46 are attached by rivets 48 to such assembly with one element of the pair on each side of the stator plate 36 and rotor plate 33, respectively. One reason for this symmetrical arrangement is to minimize the electrical field which passes through the insulat ing stator plate 36 and insulating rotor plate 33 when signal voltages are transmitted through the switch so that dielectric losses therein are minimized. Each of the

parallel shield plates

18 and 24 is placed substantially the same distance from the switch plate assembly 20 so that the switch is also symmetrical in this respect. The distances between the

shield plates

18 and 24 and contacts 40 and 4c are such that the switch forms in effect a short section of a transmission line having a characteristic impedance substantially the same as that of the coaxial cable transmission lines 32. For example, when the coaxial cables 32. have a characteristic impedance of 50 ohms and the

contacts

40 and 46 have a width of approximately A; inch, the space between such contacts and the

conductive plates

18 and 24 should be approximately one-tenth of an inch. As a result, voltage reflections in the transmission lines 32 due to the line discontinuity formed by a switch are substantially eliminated by the switch of the present invention.

In FIG. 3 the coaxial cables 32 are shown as being connected to the center contact of two oppositely disposed groups of three contacts 40 on the stator plate 36. The rotor plate 38 may be rotated by the shaft 12 between two alternate positions in order to change the connections between the coaxial cables shown. In the position of the switch shown in FIG. 3 the input signal can enter the switch through one of the transmission lines 3-2, then pass through the connection formed by fixed contacts 40 and the movable contact plates 46 and by the connecting transmission line 2 to the other transmission line 32 which may be the output transmission line. Moving the rotor plate 38 counterclockwise to its alternate position will cause the signal to move through the connecting transmission line 54 so that it may be attenuatedby an attenuator 56, or otherwise modified by any other suitable modifying means, before it is transmitted to the output transmission line. A greater number of switch contacts can be employed on the switch plate assembly for any switching purpose involving coaxial cable transmission lines or the like, usually with some loss of symmetry of the switch and some lack of continuity of the transmission line.

It should be understood that many variations in the detailsofthe present invention may be made without departing from the spirit of the present invention.

other than circular, and the type of

connectors

40 and 46 can be varied without departing from the scope of the present invention. Therefore, it is not intended to limit the present invention to the preferred embodiment de-' scribed above but the scope of the invention should be determined solely by the following claims. i

. We claim:

1. A switch to change the electrical connectionsbe For example, theshape of the

plates

10, 18, 20 and 24 may be.

switch means including switch contacts positioned betweenthe shield plates for interconnecting the other conductors of said transmission lines in a plurality d of ditferent ways by movement of said switch means, and g I support means to hold said shield plates and said switch contacts in proper spaced relationship to form a trans mission line section having substantially the same characteristic impedance as said transmission lines. I

2. A switch to change the electrical connections between a plurlity of transmission lines each having a pair of conductors and having similar characteristic impedances, comprising:

shield means including a pair of spaced shield plates to provide a common connection for the ends of one of for interconnecting said fixed contacts in a plurality of ditferent ways by movement of said switch means, and 7 support means to hold said shield plates, said fixed contacts and said movable contact in proper symmetrical spaced relationship to form a transmission line section having substantially the same characteristic impedance as said transmission-lines.

3. A switch, used to change the electrical connections between'a plurality of coaxial cable transmission lines having inner and outer conductors and having similar characteristic impedances, comprising:

shield means including a pair of spaced shield plates to provide a common connection for ends of the outer conductors in said transmission lines,

switch means including a plurality of fixed switch contacts positioned between said shield plates to provide a plurality of spaced insulated connectors adapted to be connected to ends of the inner conductors in said transmission lines,

switch means also including at least one movable switch contact positioned between said shield plates for interconnecting said fixed contacts in a plurality of ways by movement of said movable contact, and support means to hold said movable and fixed contacts approximately midway between said shield plates to form a transmission line section having substantially the same characteristic impedance as said co- 7 axial cable transmission lines;

4. A switch, used to change the electrical connections between a plurality of transmission lines having similar characteristic impedances, comprising:

a pair of spaced shield plates of electrically conductive 7 material adapted to provide common connections for the ends of shield conductors in said transmission 7 lines, 1 A a fixed switch plate having a plurality of insulated fixed switch contacts positioned between said pair ,of shield plates and adapted to be connected to the ends of signal conductors in said transmission lines, .a'rotatable switch plate having at least one movable contact positioned between said shield plates for interconnecting said fixed contacts in a plurality of ways by rotation of said rotatable switch plate, and support means to hold said fixed and movable switch plates approximately midway between said shield plates to form a transmission line section having substantially the same characteristic impedance as 7 said transmission lines. 5. A-switch for changing the electrical connections betweena plurality of electrical transmission lines having adapted to be connected to the shield conductor in said transmission lines,

a stator plate of insulator material mounted between said shield plates and having a hole therein,

d on said shaft for rotation therewith inside said hole in said stator plate, a plurality of movable metal contacts attached to said rotor plate in spaced relationship adjacent the pea rotor plate of insulator material mounted between 5 riphery thereof for movement with said rotor plate. said shield plates and inside said hole for rotation a plurality of fixed metal connectors attached to said with respect to said stator plate, stator plate in spaced relationship and extending raa plurality of movable metal contacts attached to the dially from said hole in said stator plate so that one surface of said rotor plate in spaced, insulated relaend of said connectors is positioned adjacent the petionship adjacent the periphery thereof for movement riphery of said hole and is adapted to engage said with said rotor plate, contacts on said rotor, and the other end of said conand a plurality of fixed metal contacts attached to the nectors is positioned adjacent the outside edge of said surface of said stator plate in spaced relationship and stator plate and is adapted to be connected to the extending radially from said hole so that one end of signal carrying inner conductor of said transmission each of said fixed contacts is positioned to engage lines, said movable contacts on said rotor plate, and the said plurality of contacts and said plurality of connecother end of said fixed contacts is adapted to be contors being accurately positioned between said pair of nected to the signal carrying conductors in said transshield plates in order to form a transmission line secmisslon lines, tion whose characteristic impedance is substantially and means to support said shield plates in proper spaced the same as the characteristic impedance of said relationship with respect to said stator plate and said rotor plate to form a transmission line section having transmission lines. 8. A coaxial line switch to change the electrical connecsubstantially the same characteristic impedance as tions between a plurality of coaxial cable transmission said transmission lines. lines each having substantially the same characteristic im- 6. A switch for changing the electrical connections bepedance, comprising: tween a plurality of electrcal transmission lines having a support member having a detent switch positioning substantally the same characteristic impedance comprismeans thereon,

a pair of spaced shield plates of conductive material ing: a shaft rotatably mounted on said support member,

a plurality of fastening elements fixedly mounted on adapted to be connected to the shield conductors in said support member, said transmission lines, a pair of substantially parallel spaced shield plates of a stator plate of insulator material positioned between electrically conductive material fixedly mounted on said shieldplates and having a hole therein, said fastening elements in spaced relationship and a rotor plate of insulator material mounted between 7 adapted to be connected to the outer conductor of said shield plates and inside said hole for rotation said coaxial cables with the shield plate nearest said with respect to said stator plate, support member having a hole through which said a plurality of movable metal contacts attached in pairs shaft extends while spaced from said nearest shield to the opposite sides of said rotor plate with respect plate, to said shield plates in spaced, insulated relationship a stator plate of insulator material having a substantially adjacent the periphery thereof for movement with circular hole therein fixedly mounted on said fastensaid rotor plate, ing elements and spaced between said pair of shield and a plurality of fixed metal contacts attached in pairs plates, said stator plate having two opposite side to the opposite sides of said stator plate with respect surfaces, to said shield plates in spaced relationship and exa substantially circular rotor plate of insulator material tending radially from said hole in said stator so that coaxially mounted on said shaft for rotation there one end of each of said connectors is positioned adwith inside said hole in said stator plate, said rotor jacent the periphery of said hole adapted to engage plate having two opposite side surfaces, said contacts on said rotor plate, and the other end a plurality of movable metal contacts attached in pairs of said connectors is positioned adjacent the outside to the opposite sides of said rotor plate with respect edge of said stator plate adapted to be connected to to said shield plates in spaced relationship adjacent the signal carrying conductors in said transmission the periphery thereof for movement with said rotor lines, and plate, means to support said stator plate and said rotor plate a plurality of fixed metal contacts attached in pairs to approximately midway between said shield plates the opposite sides of said stator plate with respect to to form a transmission line section having substansaid shield plates in spaced relationship and extending tially the same characteristic impedance as said transmission lines. 7. A coaxial line switch, used to change the electrical radially from said hole in said stator plate so that one end of said fixed contacts is positioned adjacent the periphery of said hole and is adapted to engage said connections between a plurality of transmission lines each having substantially the same characteristic impedance, a0 comprising:

movable contacts on said rotor, and the other end of each of said fixed contacts is positioned adjacent the outside edge of said stator plate and is adapted a support member, a shaft rotatably mounted on said support member, a plurality of fastening elements fixedly mounted on to be connected to the signal carrying inner conductor of said coaxial cables, and a plurality of insulating spacers accurately positioning said support member, 5 said plurality of pairs of movable contacts and said a pair of spaced shield plates of electrically conductive plurality of pairs of fixed contacts approximately material fixedly mounted on said fastening elements midway between said pair of shield plates in order to in spaced relationship and adapted to be connected to form a transmission line section whose characteristic the grounded outer conductor of said transmission impedance is substantially the same as the character lines with the shield plate'nearest said support mem- 7 istic impedance of said coaxial cables. her having a hole through which said shaft extends, 9. A transmission line switch assembly comprising:

a stator plate of insulator material having a hole therea plurality of transmission lines each having a pair of in fixedly mounted on said fastening elements and conductors and having similar characteristic impedspaced between said pair of shield plates, ances,

a rotor plate of insulator material coaxially mounted shield means including a pair of spaced shield plates '2! 8 connected to one of the conductors to provide a comsame characteristic impedance as said transmission mon connection for one of the conductors of each of lines. said transmission lines, References Cited by the Examiner switch means including switch contacts positioned be- V UNITED STATES PA tween the shield plates for inter-connecting the other 5 1 891 47 12/ 2 h A conductors of said transmissionlines in a plurality of 5 1 g zf g 3555 Ways by movement of, sad W11 214401037 4/48 Wolfi 200-11 2,598,534 5/52 Gordon 20() 11 support means to hold said shield plate and said switch 2,784,379 3/57 Schunemann 333 7 contacts in proper spaced relationship to form a 1Q transmission line section having substantially the HERMAN KARL SAALBACH, Primary Examiner.

Claims

1. A SWITCH TO CHANGE THE ELECTRICAL CONNECTIONS BETWEEN A PLURALITY OF TRANSMISSION LINES HAVING A PAIR OF CONDUCTORS AND HAVING SIMILAR CHARACTERISTIC IMPEDANCES, COMPRISING: SHIELD MEANS INCLUDING A PAIR OF SPACED SHIELD PLATES TO PROVIDE A COMMON CONNECTION FOR ONE OF THE CONDUCTORS OF EACH OF SAID TRANSMISSION LINES,