US2445793A - Rotary high-frequency switching circuit - Google Patents

Description

July 27, 1948. N MARCHAND 2,445,793

` ROTARY HIGH FREQUENCY swITCHING CIRCUIT Filed Aug. 19, 1944 5 Sheets-Sheet l INVENTOR. Mmm/v MAM/mw A 22A/EY QH. W \11 M( I w C.,

July 27, 1948. N. MARCHAND 2,445,793

ROTARY HIGH FREQUENCY SWITCHING CIRCUIT Filed Aug. 19, 1944 3 Sheets-Sheet 2 4 INVENTOR.

NAf/MN mmf/wa ATTORNEY ABY July 27, 1948. N. MARCHAND ROTARY HIGH FREQUENCY SWITCHING CIRCUIT Filed Aug. 19, 1944 3 Sheets-Sheet 3 IN1/EN TOR. MvT/wmv Mmc/wvo A7701? EY 53 5914129 Pa aff;

Patented July 27, 1948 UNITED STATES PATENT OFFICE ROTARY HIGH-FREQUENCY SWITCHING ClRCJ-IT Nathan Marchand, New York, N. Y., assignor to Federal Telephone and Radio Corporation, New York, N. Y., a corporation of Delaware Application August 19, 1944, Serial No. 550,196

11 Claims.

This invention relates to a mechanical switching circuit for high frequencies and particularly to a rotary high frequency switch.

An object of the present invention is the provision of an improved high frequency mechanical switch.

Another object of the present invention is the provision of a switch of the type referred to hereinabove which will not upset the electrical balance or equilibrium of the circuits in which it is arranged.

A further object of the present invention is the provision of a switch of the type described which is adapted to efliciently handle a relatively wide band of frequencies.

A still further object `of the present invention is the provision of such a switch which is adapted for continuous switching, for example, at a predetermined rate.

Still another object of the present invention is the provision of a switch of the typel described which will wear Well, has the minimum'of friction, has n'o wiping contacts and is quiet and smooth in operation.

A still further object of the present invention is the provision of a switch of the type referred to above which provides an effectively continuous shield connecting the shields 'of the transmission lines between which switching occurs. y

Other and further objects oi the present invention Will become apparent and the foregoing will be best understood from the following description of an embodiment thereof, reference being had to the drawings, in which:

Fig, 1 is a vertical sectional view taken longitudinally through themiddleof a switch embodying my invention and further showingv the mechanical connection thereof to a motor;

Fig. 2 is atransverse sectional view taken along the lines 2-27 of Fig. 1;

Fig, 3' is a longitudinal sectional View taken along the lines 3-3 of' Fig. 2;

Fig. 4 is a view similar to Fig. 2 showing the coupling plates moved under one of the coupling conductors; and

Fig. 5 is a transverse sectional viewV taken along the lines 5 5 of Fig. 4;

Referring now to the drawings, the switch I is provided with a metallic housing 2l comprising 2 a top wall 3, side walls 4 and 5, a bottom 6 and end Walls I and 8.

A coaxial line section 9 is disposed in the center of the housing and consists of two portions, a right portion lli and a left portion II having respectively inner conductors I2 and I3, and outer conductors Ill and I5, said inner conductorsl being connected together at their inner ends, said outer conductors being separated by a gap I6 separating their inner ends. The outer end of' outer conductor l5 is closed as indicated at I'l, while the outer end of outer conductor It is open as indicated at I8. Inner conductor I3 is larger in diameter than inner conductor I2. The outer end of inner conductor I2 extends through an opening i9. in the end Wall 'l of the housing and is split as indicated at 2D. The split end 20 is surrounded b-y a threaded member 2l, which together serve as an external terminal or socket 22 for connection to a coaxial line, which connection may be made by means of a suitable plug device.

Coaxial line 8 -is surrounded by a concentric cylindrical metallic shield 23 which is in turn surrounded by a larger concentric metallic cylindrical member 24. The member 24 is divided into two arcuate segments: a large arcuate segment 25 which serves as a grounding plate, and a smaller arcuate segment 2B which is split transversely across the middle thereof to provide a gap 22.? separating arcuate coupling plates 28 and 29 which serve to switch current to and from Various transmission lines. In the embodiment illustrated, segment 25 occupies approximately 270 of the circle formed by member 24' and segment occupies about The inner ends of plates 28 and 29, adjacent gap 2l, are connected to the corresponding inner ends of outer conductors I4 and i5 respectively of the coaxial line, adjacent gap I6, by means of two conductor members 30 and 3l which pass through an opening 32 in the shield 23. Conductor members 3D and 3l act as va balanced dual transmission line.

Outer conductors I4 and I5 of coaxial line section B, shield 23 and cylindrical member 24 including the large segment 25 and coupling plates 28 and 29 are all adapted to rotate together around the inner conductors I2 and I3 which remain stationary. For thisl purpose circular end plates 33 and 34` are arranged at opposite ends of said rotatable cylinders, and serve to close the openings therebetween at the youter ends thereof and to mechanically nx them together so that they will all rotate simultaneously. A ballbearing 35 is provided between rotatable end plate 33 and end wall 'l of the housing and a similar bearing 36 is likewise arranged between end plate 3d and end wall 3. The rotatable portion of the structure may be driven by any suitab-le motor 3l by means of a shaft or similar mechanical transmission means 33 which may be attached to end I'I of outer conductor I5.

A plurality of coupling conductors 39, of which there are :tour in the embodiment herein described, are symmetrically arranged around at equal distances from and closely adjacent the path of cylindrical member 24. Energy is transferred between said coupling conductors 313 and the coupling plates 29 and 29 as said plates pass adjacent sai-d conductors. Coupli-ng conductors 39 each consist of a thinner portion 40 and a thicker portion 4| (see Fig. 5). Conductors 39 are mechanically supported by end walls 'I and 8 but are electrically insulated therefrom by insulating means 32 and 43. The thinner portion l0 of each .of conductors 39 terminates in a still. thin-- ner portion M which is split at the end and pro- Ajects through an opening 35 in wall 1 into a .threaded 'member 413 to thus form. a socket M similar to socket 22 hereinbefore described. Fixed shielding plates 56 (see Fig. 2) are arranged between each of the coupling conductors 33 and are supported by and electrically connected to the vwalls of the housing. l

In use switch I is connected by means of socket yany current ilowing on the outside conductors of 'the coaxial lines attached to switch I cannot enter said switch or the coaxial lines attached thereto.

Socket 22 may be the input terminal and sockets 4l the output terminals or, vice Versa, sockets lll' maybe the input terminals and socket 22 the output terminal. If, for example, switch I is used in a direction finding apparatus, then four antenna elements are connected to sockets il and socket 22 is connected to .the receiver.

nected to the receiver, thus providingr the required antenna .switching for such systems. On the other hand, in a beacon system, the transmitter kwould be connected to socket 22 thus making it the input terminal and sockets 4l would be connected to various antennas and thus be fthe output terminals.

Switch I is designed to handle a wide band of high frequencies without dissipating an undue amount of energy, or causing imbalances, or prou ducing material phase distortion, and with a minimum of impedance mis-matching. In accomplishing this, the electrical dimensions of the -Various elements of the switch are relatively critical.

The following are substantially the electrical ,dimension-s of the elements of the switch as ex Zpressed in terms of the mean wavelength, A, of the I By continuously .f rotating the rotatable pontion of said switch, the Various antenna elements are alternately conground orwide flat plane.

band of frequencies at which the switch is designed to operate:

Coupling conductors 39 each Thinner portion 40 of each of coupling conductors 39 Thicker portion 41 of each of coupling conductors 39 Il ll ely elw Niv Coupling plates 28, and 29, as measured from gaph27 to end plates 33 and 34 respectively eac Metallic shield 33 as measured from end plates 33 to 34 Outer conductor 14 and inner conductor 12 as measured from gap 16 to end 18 Outer conductor 15 and inner conductor 13 as measured from gap 16 to end 17 (Because of the capacitance eiect across the gaps 16 and 27 the lengths of the above must be varied slightly to attain f thc mean of the band of wavelengths covered.)

Assuming that the sockets 4l are input terminals and socket 22 is the output terminal, energy from the coaxial lines connected to sockets 4l will flow into the switch (along the inner surfaces) of threaded members 45 and the outer surface of 1M thus providing a ow along coupling conductors 39. Assuming further that the instantaneous direction of the curr-ent is as indicated by the arrow A-I in Fig. 5, current A-I flows along both the Ithi-nner portion 40 and the thicker portion il of coupling conductors 39.

Coupling conductors 39 may be considered in relationship to the arcuate segments 25 and 2B as being a single wire transmission line over ground or over `a wide flat plane. Currentsv `along the line induce currents of opposite direction on said Likewise when the larger arcuate segment lor grounding plate 25 is adjacent a particular coupling conductor 39, current will flow on the outer surfaceof said grounding plate 25 in a direction opposite that indicated by arrow Aw. Because of the capacitan-ce effect -between the end walls 'I and 8 and the end plates 33 and 36, the current flowing on the outside ci the grounding plate will ilow across the space between the end plates and end members and out along the inner surface of threaded members 46. `Thus it will be seen .that when the grounding plate 25 is under one of the coupling conductors, the energy delivered will be short-circuited to ground (considering the inner surface of the outer con ductors of the attached coaxial lines to be at ground potential).

On the other hand, when the coupling plates 28 and 29 are under one of the coupling conductors 39, the current indicated by arrow A-I,

' in Fig. 5, will cause a current now along the outer surfaces of plate 29 in the direction indicated by arrow A--2 in Fig. 1 and along the outer surface of plate 28 in the direction indicated by arrow A-3 in the same ligure. Current A-2 will tend to divide in two directions, as indicated by arrows A-4 and A-5. Since, however, the inner surface of plate 29 .and the opposing outer surface of metallic shield '23 form a shorted quarter wavelength section 48 at the mean frequency, at said lfrequency no current will `flow along the di.-

rection A-Bi However, as the frequency departs from said mean frequency; the current will current- 'ow is, however, balanced by al similar current flow through theA opposite shorted quarter wavelength section at the mean frequency includ'- ing the inner surface of coupling. plate 28. Indicating' theinner ends of members 28 and 29 as pointsPrand Pb, it willV be seen that in accordance with Kirchoffs law, there will tend to ow toiiv-ard point Ps, currents A-E, andv A-!, equall tocurrent A-3 flowing away from said point. However, atr the mean frequency, there will be no current A-T since the impedance of' the closed quarter wave section will be so great as to prevent current flow. However, as this mean frequency is deviated from, there will be av current A-'I varying in magnitude in accordance with the deviation from said mea-n frequency. The current A-T and the current A`5 will, however, balance each other so that the potentials at points Ps andPb will-be equal and opposite. Conductors and 3| will, therefore, act as a balanced dual transmission line.

The dual transmission lines- 3| and 3Q, is connected to points Pc and Pd on opposite sides of gap l'6. At point Pc, current indicated by arrow A'-4^` tends to split in two directions indicated by A-8 and A-9. Likewise at point Pd, current indicated by the arrow A-B tends to go in two directionsv as indicated by the arrows A-IU and A-l Since, however, the outside of outer conductors l5l and I6` and the portions of the inner surface of metallic shield 23 facing them each form shorted quarter wavelength sections 5D and 5`|`, at meanl frequency currents A--B and A-II will be extremely small or negligible as explained hereinabove-in regard to currents A-5 and A-'L As mean frequency is deviated from, currents A--B and A'-| I, will reach some magnitude in accordance with the amount of said deviation but said currents will. balance each other and therefore not upset the balance of lines 3U and 3|.

Currents A-S'and A-l 0 will induce a current A-IZ in inner conductors |3 and I2 respectively. Current A|2 will travel outwardly through socket 2'2 to the inner conductor of the coaxial line to which said socket is connected. Currents A-S and AA--I'U which are in the same direction will reach the inner surface of said. coaxial cable by. virtue offthe capacitance effect across the open end'35` of the outer conductor I4 to the adjacent portions ofA end member 'l as wellv as through the galvanic. connection provided 'by the ballbearing 35.. through opening. I9 along the inner surface of threaded member 2| and thence .along the inner surface of the outer conductor of the coaxial cable secured to said threaded member 2|.

While the currentflowing through lines 30 and 3| is. balanced due to the arrangement of the aforementioned closed quarter wave sections 48-5|, as the mean frequency is deviated from, the lengthA of the sections is no longer a quarter wave and'these sections function primarily as inductances or capacitances introducing a given amount of phasedistortion. This phase distortion is substantially compensated, however, by an opposite phase distortion produced in the openended quarter wave sections 52 and 53 in series with points Pa and Pc, said section 52 consisting of the thicker portion 4| of coupling conductor 39 and the surface of coupling plate 29 arranged thereunder, and section 53 consisting of the inner Said current will then flow outwardly 6. surface of outer conductor |-'5 of coaxial line` 91 and the inner conductor I3' of: said. coaxial line:

In order to limit impedance mismatching to` a: minimum, thesurge impedances ofl the variousl sections forming said switch are calculated at the mean` fre'quencyxas follows.

Assuming that the input impedance aspresented4 at socket 41 isZm, then if Zai isfthe surge impedance of the open-ended quarter wave section 54 consisting of the thinner portion 4111 off coupling conductor 39 and the coupling; pla-te 26 acting as'the ground plane therefor, then,

e* -zg-jzgnia Maz., an 01 (3)' where 0=the electrical length in degrees of section 52- Simplifying Equation 3 .Za 1 -JZM cotan 0 It can be seen from Equation 5 that the only term preventing a perfect transition from socket 4T to points Pa and Pb is the cotangent square term in' the denominator. As long Zia and' Zlio or 2Z4s is kept at least twice as large as Z54, Equation 5 shows that an excellent transition will occur fromV socket 4l to points Pa and Pb at a three-to one frequency range.

A similar transition from points Pe and Pd to socket 22l is likewise obtained using the foregoing equations and making the following substitutions: Substitute ZL for Zin Z for Z4s Z5r for Z45 Z55 for Z54- o fore where ZL is theload impedance at socket 22"; Z55 isthe surge impedance of the coaxial section 55 consisting or innerV conductor |2` and outer conductor 4 and" 0 is the electrical length of` said section 55';

In the foregoing equations, the capacitance' eiect across gapsA 2T and i6' is neglected. Thesev gaps Should-preferably be as small as practicable'. By employ-ing the relative constants as indicatedi in the above equations, the input impedance is matched to points Pa and Pb and the load impedance is matched to points Pc and Pd, thus producing matching between the load and input impedances of the switch` 7 While I havedescribed above the principles of my invention in connection with specific apparatus, it is to be clearly Iunderstood that this description is made only by way of example and not as a limitation on the scope of my invention as set forth in the objects and theclaims.

Iclaim: 1. A high frequency switch comprising a plurality of terminals, an elongated conductor connected to one of said terminals, a conductive switching member adapted to be moved into and out of coupling relationship with said conductor and in said coupling relationship extending a substantial distance adjacent to and parallel with said conductor, said member having a transverse gap intermediate the ends thereof separating it into two parts, a second elongated conductor connected to another of said terminals, a coupled conductive member coupled with and extending adjacent to and parallel with said second elongated conductor, said coupled member having a transverse gap intermediate the ends thereof separating it into two parts, and means connecting the ends of said switching member facing each other across its gap with the ends of said coupled member facing each other across its gap 2. A high frequency switch according to claim 1, wherein said coupled member is the outer conductor of a coaxial line section, and said second elongated conductor is the inner conductor of said coaxial line section.

3. A high frequency switch according to claim 1, wherein said coupled member is the outer conductor of a coaxial line section and said second elongated conductor is the inner conductor of said coaxial line section and wherein said switching member is relatively wide in comparison with said first-mentioned elongated conductor, said firstmentioned elongated conductor and sai-d switching member forming, When they are coupled together, a single conductor over a wide plane transmission line section.

4. A high frequency switch according to claim 1, wherein said coupled member is the outer conductor of a coaxial line, said second elongated conductor is the inner conductor of said coaxial line, said switching member is carried on said coupled member and said coupled member is adapted to be rotated about said second elongated conductor to thereby move said switching member in a circular path, and said first-mentioned elongated conductor is so arranged adjacent said path, so that upon rotation of the coupled member past the switching member, the switching member is brought into and out of coupling relationship with said first-mentioned elongated conductor.

5. A high frequency switch according to claim 1, wherein said -coupled member is the outer conductor of a coaxial line whose inner conductor is said second elongated conductor, said outer conductor being adapted to be rotated about said inner conductor, said switching member is relatively wide and arcuate in cross section and is carried on said -outer conductor to thereby travel in a circular path upon rotation of said outer conductor, said first-mentioned elongated conductor being so arranged adjacent said path that upon rotation of said outer conductor said switching member is brought int-o and out of coupling relationship with said first-mentioned elongated conductor.

6- A high frequency switch comprising a plurality of terminals, a central elongated conductor connected to one of said terminals, a plurality of other elongated conductors arranged around said.

central conductor and each connected vto one of the other terminals, a conductive switching member adapted to be moved into and out of coupling relationship with one `of said other conductors at a time, and in said coupling relationship extending a substantial distance adjacent to and parallel with the conductor to which it is coupled, said member having a transverse gap intermediate the ends thereof separating it into two parts, a coupled conductive member coupled with and extending adjacent to and parallel with said central i conductor, said coupled member having a transverse gap intermediate the ends thereof separating it into two parts, and means connecting the inner ends of said switching member at its gap with the ends of said coupled member at its gap.

7. A high frequency switch according to claim 1 in which said means consists of a balanced `dual transmission line.

8. A high frequency switch according toclaim4 l in which said means is a balanced dual transmission line, and further including a pair of effectively quarter wave shorted sections as measured at the mean frequency of the band of frequencies at which said switch is designed to operate, one-l leg of one of said quarter wave sections being connected with one leg of the other quarter wave section and the other legs of said sections constituting the parts of said switching member, and a second pair of similar quarter wave sections, one leg of each of said sections of said secondpair being comm-on with said connected leg of each of `said sections of said first pair and the other legs of said sections of said second pair constituting the parts of said coupled member.

9. A high frequency switch according to claim` l. in which the surge impedance of the section consisting of the first-mentioned elongated conclaim 1, wherein said means consistsl of a dual transmission line and further including means for balancing the electrical phenomena on said dual transmission line.

11. A high frequency switch according to claim 1, wherein the cross-sectional area of said elongated conductors is enlarged at vthe portions thereof on the side of the gap opposite the terminals.

NATHAN MARCHAND.

REFERENCES vCITED The following references are of Vrecord in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,223,061 Ducati Nov, 26, 1940 2,244,023 Sauer June 3, 1941

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