US2452113A - Switch for high-frequency electrical oscillations - Google Patents

Description

0a. 26, 1948 D. c. ESPLEY 2,452,113

SWITCH FOR HiGH-FREQUENCY ELECTRICAL OSCILLATIONS Filed March 50, 1946 INVENTORI DENNI CLARK ESPLEY, a /4 ATTORNEY.

Patented Oct. 26, 1 948 SWITCH FOR HIGH-FREQUENCY ELECTRICAL OSCILLATIONS Dennis Clark Espley, North Wembley, England,

assignor to The General Electric Company Limited, London, England Application March 30, 1946, Serial NOI 658,404

In Great Britain March '7, 1945 Section 1, Public Law 690, August 8,. 1946 Patent expires March 7, 19,65

8Claims. (01.11844) This invention relates to switches for high-irequency electrical oscillations and is an improvement in or modification of switches of the type described and claim-ed in United States Patent No. 2,404,832, issued July 30, 1946, in the name of Dennis Clark Espley, whereinafter referred to as the parent specification.

The parent specification describes and claims a switch for high-frequency oscillations of wave length A, corresponding to frequencyf, comprising a uniform line substantially of length X/4, where q is an integer, having its members connected at one end to a pair of terminals, being the terminals the impedance between which the switch renders alternatively very large or very small, means for approaching a conductor to the other, open, end of the line so as to provide an impedance shunting the said open end which is the impedance of a capacity C, and an impedance element X of such a nature and value and constantly associated with the said pairof terminals in such a mannerthat, when the said conductor is near the said open end, the impedance between the said pair of terminals assumes substantially one of the values zero and infinity and, when the said conductor is far from the said open-end, the impedance between the said pair of terminals approaches the other of the said values.

In some circumstances it may not be possible it may be desirable for it to be d-ifierent from qi/ for example, in view of dimensional limitations or requirements in the apparatus of which the switch forms part, and the object of this invention is to provide means for obtaining the required switching action when the length of the line is substantially diiferent from qA/ l.

Figure 1 of the drawing is a schematic diagram of a switch according to the invention. 7 i

Figure 2 is a schematicv diagram, withsor'ne parts in section, of another embodiment" of the invention. The principles underlying the invention will now be described with reference'to the afccompanying drawing which shows schematic-ally a length L of uniform'line, of characteristic impedance Z0, connected across the said pair of terminals I, 2 and terminated with an impedance Z2 Z and Z5 are impedance element's p rmanently for the length of the uniform line to be 'qA/i, or

associated in parallel and series respectively with theterminalsilw l V I 1f Z1 is the impedance looking into the terminals I, 2 then when Z 2 andzs il;

ZO( 2'+J' 6 (Z +jZ tan 0 v where c='21rL/ This is the well-known equation for the input impedance of a length of uniform line terminated with'impedance Z2.

r If Zp and Z5 have-.other values, we have from (1) and the ordinary rules for combination of impedance in series, and in parallel.

If ZA is the-value of Z1 when Z2: 00 (corresponding to the-said conductor withdrawn from the open' end of the line) and Z3 is the'value when Ze l/inc (corresponding to the said conductor approached close to the open end of the line) where 5:211, then To obtain perfect switching across the terminals l 2,:we must have'Z4= 0 or w and ZB= or 0 respectively. If these pairs of values ,of' ZA and Zn are. substituted into Equations 3 'and 4, then for'anyparticular value of ten 0 the equations may be solved for Z8 and Z i. e. for any particular length of line it is possible to find from these equation'values'of Zs and Zp which will give rise to the switching action required; the aforesaid oblectof the invention may thereby be attained.

According to the invention a switch for highfrequency electrical oscillations of wavelength 7\, corresponding to frequency 1, comprises a uniform line :of length L'appreciably different from q \/4, where q is an integer, having its members connected at one end to a pair of terminals, means for approaching a conductor to the other, open, end of theline so; as to provide an impedance shun-ting the said-openend which is the impedanceof a capacity C, and one or more impedance elements of such nature and such a value and constantly associated with the said terminals in such a manner that when the said conductor is near the said open end the impedance between the said pair of terminals assumes substantially one of the values zero and infinity and when the said conductor is far .from the said open end the impedance between the said pair of terminals assumes substantially the other of the said values. In the parent specification the-length ofline specified isqA/ i as aforesaid. If-q is .odd then tan 9=' and we have the switching action 211:0, ZB= if Zs=-0, and Zn --fiZo wC' If q is even, tan :0 and we have :the switching action ZA=, ZB=0 if I V Zs=:i/wC', arid'z These are the arrangements described in the parent specification.

These arrangements have the advantage that only one impedance element is required whereas with arrangements in accordance with the invention two impedance elements, one in series and one in parallel, will in general be required; there are,however, special cases of the arrangement in accordance with the invention wherefonly one impedance element is required; I These special cases require a particular length of line, as will now be shown, and-may be useful where this particular length is possible or desirable.

Thus putting Zs=0in Equations 3 and 4 it follows that the switching action ZAI'Z"; Ze=0 wil1 be obtained if n r f v=i 0 wC', and tan 0:1/ZowC' (7) In this arrangement Zp is inductive and the minimum value of L is less than M4.

Putting Z 1: in Equations 3 and 4 it follows that the switching action ZA=0, 23: will be obtained if oscillations, a plurality ofswitches eachin accordance with the" invention and acting as attenuators in series maybe provided at spaced points,

preferably separated by distances M4, along the line 'inorder-to increase the attenuation, as described in United States Patent'No. 401,863, issued June 11, 1946, in the name of Dennis Clark Espley in connection with the parent application. arrangement is shown schematically in Fig.2 of the accompanying drawing which shows a section through the rlevantpart'sl' l -Iere the main concentric transmission line consisting of outer conductor I and inner conductor 2i's adapted to convey electrical oscillations from a source 3 tea power c'onsumingdevice 4 and has branched 01f from itat points spaced M4 aparttwojswitches in accordance with the invention; these switches consist of concentrioline, stubs of lengths L having outer conductors 5, 5' joined to the outer conductor I and inner conductors 6, 6' joined to the inner conductor 2 through transmission-line stubs represented by the dotted circles 1, l acting as impedance elements in series with the input of the switching stubs; these transmission-line stubs may consist of parallel wire lines surrounded by a cylindrical conductor connected to the conductor l as described in the parent specification.

The first switching stub is branched off at a distance M4 from the end of the main transmission line to which the source 3 is connected.

Also branched off from the main transmission line at the same points as the said switches are concentric line stubs consisting of outer conductors 8, 8 joined to the outer conductor 1 and inner conductors 9, 9 joined to the inner conductor '2 so as to act as impedance elements in parallel with the input of the switching stubs.

The length of each switching stub is appreciably different from any multiple of M4 and the allel' impedance elements are adjusted with respect. to L as indicated by Equations 3 and 4 to provide the necessary values of 25 and Z1: to produce the required switching action on the approach or removal of the conducting plates to, .l 0' from the open ends of the switching stubs.

I claim: g

. 1.,A. switch for high-frequency oscillations of frequency f comprising a stub including a concentric uniform line of length L substantially different from ql/ l where q'includes all integers of odd and even gender, and is the wave length along the said line corresponding to the frequency f, the members of said stub bein adapted to be connected at one end of the stub to another uniform line which the switch is to control, the sec end end of'said stub being open, a conductor rel atively movable with respectto the open end of said stub between a first position in which said conductor and the open end'of said stub are remotely spaced and a second position in which said conductor and the open end of said stub are closely "spaced; whereby/said conductor gives rise to a cap'acitative impedance ofvalue C in said second position shunting the open end of said stub, and atleast one compensating impedance element permanently electrically connected to said" first end of the stub, .the number of impedance elements and the type and value of each impedance element and its connection to said first end of the stub being such with respect to the frequency f, the value of L, the impedance C and the characteristic impedance Z0 of the stub, that when said conductor is in one of said positions the impedance across said first end of the stub is substantially zero and when said conductor is in the other of said positions the impedance across said first end of the stub is substantially infinity. ,2. A switch according to claim 1 wherein the length L of the said stub is M/Zw where din radians is tan" (/zrfZpC) and comprising an inductive compensating impedance element of inductance Z4 0 connected in parallel with the said first end of the said stub. I

:3. An electric system comprising a uniform transmission line connected at one end to a source othigh-frequency energy and at the other end tov a current consuming device, said system ineluding a switch as set forth in claim 2 for controlling the supply of energy from said source to the current consuming device, the stub of said switch being connected to said uniform transmission line at an integral numberof quarter wave lengths from that end of the transmission line which is connected to the source of high-frequency energy.

4. A switch according to claim 1 wherein the length L of the said stub is N9/2'n' where 0 in radians is tan- (-21rfZoC) and comprising a capacitative impedance element of capacity C connected in series with the said first end of the said stub.

5. An electric system comprising a uniform transmission line connected at one end to a source of high-frequency energy and at the other end to a current consuming device, said system including a switch as set forth in claim 4 for controlling the supply of energy from said source to the current consuming device, the stub of said switch being connected to saiduniformtransmission line at an integral number of quarter wave lengths from that end of the transmission line which is connected to the source of highfrequency energy.

6. An electric system comprising a uniform transmission line connected at one end to a source of high-frequency energy and at the other end to a current consuming device, said system including a switch as set forth in claim 1 forcontrolling the supply of energy from said source to the current consuming device, the stub of said switch being connected to said uniform transmission line at an integral number of quarter wave 6 lengths from that end of the transmission line which is connected to the source of high-frequency energy.

7. A switch according to claim 1 wherein at least one said compensating impedance element is provided by a length of transmission line.

8. An electric system comprising a uniform transmission line connected at one end to a source of high-frequency energy and at the other end to a current consuming device, said system including a plurality of like switches each as set forth in claim 1 for controlling the supply of energy from said source to the current consuming device, the stubs of said switches being connected to said uniform transmission line at an integral number of quarter wave lengths from each other and from that end of the transmission line which is connected to the source of high-frequency energy.

DENNIS CLARK ESPLEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,395,870 Hiehle Mar. 5, 1946 2,396,708 Leeds Mar. 19, 1946 Certificate of Correction Patent No. 2,452,113. October 26, 1948. DENNIS CLARK ESPLEY It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 2, lines 6 and 7, equation (1), right-hand portion thereof, for 1 :3 tan 0) tanw read hnes 14 and 15, equation (2), right-hand portion thereof, for tan 0 ad line 36 for the Word equation read equations; column 4, line 64, claim 2 tan 6) for ZRC read Z 0;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 18th day of January, A. D. 1949.

THOMAS F. MURPHY,

lm'sta nt Oowwnissioner of Patents.

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