US2591910A

US2591910A - Electron discharge amplifier device employing hollow resonator

Info

Publication number: US2591910A
Application number: US704225A
Authority: US
Inventors: Barford Norman Charles
Original assignee: EMI Ltd
Current assignee: EMI Ltd; Electrical and Musical Industries Ltd
Priority date: 1945-09-10
Filing date: 1946-10-18
Publication date: 1952-04-08
Anticipated expiration: 1969-04-08
Also published as: FR935027A

Description

A ril 8, 1952 N. c. BARFORD 2,591,910 ELECTRON DISCHARGE AMPLIFIER DEVICE EMPLOYING HOLLOW RESONATOR Filed Oct. 18, 1946 rwswroR NORMHN c. I36 R F RD Patented Apr. 8, 1952 Great Britain Applicationbctolier 18, 1946, Serial No. 704.2 In'Great Britain September 10, 1945 e ELECTRON DISCHARGE AMPLIFIER DEVICE EMPLOYINGIIOLLOW RESONATOR Norman Charles Barford, Southend, England, as-

signor to Electric & Musical Industries Limited, Hayes, Middlesex', England, I a company "of Section 1', Public Law, 690, August 8, 1943 f 'Patent expires September 10,1965 iolaims; (c1. 315-'--6) x y r This invention relates to electronfdischarge devices of the kind in which signals to jbe amplifiedare fed to a hollow resonator often termed a buncher,- tuned to the frequency of the signals which serves to impart velocity modulation to a beam of electrons projected through aggap formed therein, the velocity-modulated beam manating from the buncherbeing thenallow ,to pass through a drift space in which the veloc ty-modulated beam becomes charge-densitymodulated, after which the beam is caused to pass through a gap in a further resonator, frequently termed the catcher, so as to impart energy thereto. Amplifier devices of this kind operating, for example, at about 3000 megacycles per second may have a bandwidth (between the "half-power points) of about 10 megacycles per second. Such a relatively narrow passband may be undesirable in some cases and, accordingly, it is the object of the present invention to provide an improved electron ,discharge amplifier device employing hollow resonators in which the passband of the device as an amplifier is effectively increased.

According to; the invention an electron discharge amplifier device of the kind referred to is provided in which one or more further resonators is or are arranged between the bunchenand the catcher resonators so 'as to be traverfi i by the electron beam, said one or more further resonators being tuned to a frequency or *fr'equencies slightly different from the frequencies to which the buncher and catcher resonators are tuned so as to increase the pass-band of the amplifier device.

In order that the said invention may be clearly understood and readily carried into effect, it will now be more fully described with reference to the accompanying drawings,inwhich:

Figure 1 is an explanatory curve; Figure 2 illustrates diagrammatically an elec tron discharge device constructed according to one embodiment of the invention, and

Figures 3 and 4 are further explanatory curves.

The known form of electron discharge'amplifier device hereinbefore referred to usually has a bandwidth (between the half-power of the order of 10 megacycles per secoiid at frequencies around 3000 megacycles per second. In such an amplifier device the output/frequency response curve for a fixed power source of input would be similar to that indicated in Figure 1 of the drawings. In this case it will be seen that at the resonant frequency in of the resonator maximum output is obtained whereas at frequencies removed from the resonant frequency a smaller output is obtained. accordance with the present invention one ormore further rs'onators is or are arranged between the buncher and catcher resonators so as to be traversed by the electronbeam of thedevice, such resonator or resonators beingjtuned to a-frequency or frequencies slightly different from the frequency to which the buncher' and catcher resonatorsare tuned. A typical form of electron'discharge amplifier device embodying the invention is shown in Figure 2 of the drawings and comprises a cathodel, a cathode shield 2, a toroidal first or buncher resonator 3', a toroidal output or catcher resonator 4, and a target 5, theenvelope of the"'-" device being omitted. These two resonators function in the manner known in the art, input signals applied to the first resonator 3-via a coupling loop Sand concentric "line-1 causing'the electron stream emanating from the cathode I and passing through the resonator 3 to become velocity-modulated and inthedriit' space be tween the resonator 3 and resonator d-the velocity-modulated stream becomes charge-densitymodulated and on passing through the resonato 4 imparts some of its energy thereto; energy being abstracted from this resonator via" coupling loop L, 8 and concentric line 9. Two further toroidal resonators In and II are arrangedbetween reso-' nators 3 and'4 so as to be traversed'by the elec -f utron' beam, and'these resonators are tuned, to frequencies f1 and f2, that is to say, to frequencies on either side of the frequency of in to which the resonators 3 and 4 are tuned. If the resonators 3 and 4 are tuned to 3,000 megacycles, the resonators l0 and II may be to 2990 and 3010 megacycles respectively. The introduction of the additional resonators l0 and II serves to increasethebandwidth of the amplifier device and if only one intermediate resonator were employed the bandwidth of the amplifier device would be increased following the curve shown in Figure 3, whilst where two intermediate resonators are employed tuned respectively to frequencies f1 and la the bandwidth of the amplifier device would be along the lines of that shown in Figure 4.

It will of course be appreciated that the invention is not limited to the introduction of one or two intermediate resonators, since more than two intermediate resonators can be employed tuned to various frequencies removed from the resonant frequency of the buncher and catcher resonators. Further, it is not necessary where two intermediate resonators are employed to have a common wall for the two resonators as indicated in Figure 2.

3 What I claim is: An etres di char e fier d vic comprising cathode means for; generating and direct- 4 ing a stream of electrons along a beam path, input resonator means in said path adjacent said cathode means and tuned to a first frequency of the order of thousands of megacyoles forzvfi i illflv modulating said electrons, output resonator means in said path and spaced from saidvelocity modulating means and tuned to said firstfresaid stream, and other means for increasing the bandwidth of said device comprising resonator I io quency for extracting oscillatoryenergy from means in said path intermediate said' velocity,

modulating means and said energy extracting,

means and tuned to a second frequency differing from said first frequency by about ten mega cycles.

2. An electron discharge device comprising cathode means for generating and directing a e m oi l ctrons, al r ibe m pa h, inpu r s-e.

ter: means-in saidpa hadm nt a sa ho means .andtuned; to a firstjrequency for velocity lu g d,. ct n o u onat r means aid p ath and spaced from said velocity quency foriextracting oscillatory energy from Qs eam-La i m ans o in ea h ba d.-

la i am ansa d;fiu edto s ufi t, i

Width 1 sa dfis iq m eo r e na or mea said path -;int erm ediate said velocity ana ed aclu in t a i o at r t n to it a sn ies;sli htl eb ye d wc a d-lfi t quenc r pegt l 3. Ameiectron discharge device according to W ereiau a gfi f ue c s r th h s ed q zn acyc e dsa d i 4 An electron. discharge device according to claim- 2, wherein said cavity resonatorshave a mxnpawa h 5. An ielectron discharge amplifier device compris ng cathode means ior generating and directing astfeam of electrons along a beam path a first icavity resonator, tuned to a first frequency so dglsil .m ens and; sa d energy e t t v A.

, e id fier t ere om; by a t e m -Q of the order of thousands of megacycles, a second cavity, resonator tuned to a frequency differing from said first frequency by about ten ,Inegacycle a third cavity resonator-tuned to said first-frequency, and. a collector electrode, said fourcavity resonators being apertured and arranged along said beam path between said cathode means and said collector electrode in the order named with said beam path extending through the apertures of the resonators.

7. An electronic amplifier comprising cathode means for producing a stream of electrons alon a beam path, velocity modulating resonator means in said path adjacent said cathode means andtuned to a first frequency, output resonator meansin said path and spaced from said velocity modulating resonator means and tuned to said first frequency, other resonator means in said pathintermediate said velocity modulating resonatormeans and said output resonator means and tunedto a. second frequency slightly difierent from saidfirst frequency for increasing the bandwidth of said amplifier, means for coupling said velocity; modulating resonator means to an input signal source, and means for coupling said output; resonator means to a load, said resonator meansbeing coupled together only by said stream of electrons.- NORMAN CHARLES BARFORD.

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

UNITED STATES PATENTS j Number 0 Name Date 2,280,824 Hansen et a1. Apr. 28, 1942 2,414,843 r Varian et a1 Jan. 28, 1947 2,424,959 Alford Aug. 5, 1947 2,452,048 Hansen et a1. Oct.. 26, 1948.