2,416,841 Patented Nov. 12, 1946 UNITED STATES PATENT OFFICE 2,410,841 ‘TUNING ARRANGEMENT Arthur L. Samuel, Summit, N. 3., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Original application May 6, 1942, Serial No. 441,937. Divided and this application October 19, 1942, Serial No. 462,537 1 Claim. (01. 178—44) 1 .2 This invention relates to electronic devices, par ticularly for operation at ultra-high frequencies. the electron stream as hereinafter described, and each is provided with a central aperture in align ment with the axis of the electron gun 2 in order to accommodate the passage of the electron stream from said gun to the collector 3. A pair An object of the invention is to facilitate the operation and tuning of ampli?ers, oscillators and the like, especially those employing resonating of adjacent discs 2“ and M2, respectively, ‘form chambers or cavity resonators. A feature of the invention is a provision for a precise or ?ne adjustment of the tuning of a cav ity resonator comprising an adjustable branch parts of opposing walls of ,an input resonator I20. The disc 2II may have attached thereto a short tube 2 I 8 aligned with the aperture and extending chamber of such restricted dimensions compared 10 outwardly with respect to'the walls of the reso nator I20. The disc ‘2! 2 has fastened to the edge with the main cavity that the resonant frequency of the aperture therein a relatively long, ?aring of the main cavity is close to and somewhat below tube I22. Longitudinally of "the path of the elec the range of free transmission of electromagnetic tron stream a gap I2I is de?ned between the cen waves in the branch cavity so that the latter will not fully support a wave of the frequency to be 15 tral portion of the inner surface of the‘ disc 2H and the small end of the tube I22. The disc 2I3 resonated and adjustment of the size or shape of has fastened to the edge of the aperture therein the branch cavity will have a de?nite but rela a ring-shaped electrode I 24 positioned adjacent tively small effect upon the resonance of the ar to the large end of the tube I22. An annular rangement as a whole. Another feature of the invention is the provi 20 gap I23 is de?ned between the adjacent ends of the tube I22 and the electrode I22. A pair of ad— sion of a plurality of loosely coupled branch ~cav_ jacent discs 2M and 2~I5, respectively, form parts ities adjustable to resonate at the same fre of opposing walls of an- intermediate resonator quency as the main cavity or at slightly di-iferent I 23. The disc 2M supports a ?aring tube I26 frequencies, producing in either case a broad fre quency band or relatively flat transmission char 25 similar to but inverted with respect to the tube I22 with the large 'end of the tube I26 de?ning acteristic for the system. together with the upper edge of the electrode I24 an annular gap I25. The disc 2-I5 may have, at tached to its outer side and surrounding the a division of my copending application, Serial No. 30 aperture, a short tube 2H. A gap .I2'I is de?ned This application includes subject-matter orig inally disclosed in my copending application, Se rial No. 412,067, ?led September 24, 1941, and is between the central portoin of the inner surface of the disc 2!?) and the small end of the tube i216. 441,937, ?led May 6, 1942. Further objects and ‘features of the invention will be apparent from the following detailed de The walls of the resonator I22 should be con scription and the accompanying drawing, while the scope of the invention is de?ned in the ap 35 ductive, or should at least have conductive inner surfaces. The tubes I22, I25, 2I8 and 2I9 and the ring I24 should be conductive and should be conductively fastened to their respective support embodiment of the invention in a frequency con ing discs. version system employing resonating chambers or The portion of the arrangement so far de 40 cavity resonators. ‘1 scribed is similar to one disclosed and claimed in Referring to the drawing, an evacuated, insu my copending application, Serial No. 388,031, ?led lating envelope I is represented as enclosing a April 11, 1941, and assigned to the assignee of plurality of elements including a suitable source the present application. The resonator I20 may of an electron stream such as an electron gun or beam projector shown generally at 2,-and an elec 45 be connected with a suitable wave guide for sup plying incoming waves to the resonant system, tron intercepting elctrode or collector 3. The the guide being separated from the resonant electron gun 2 is provided with an electron emit pended claim. The single ?gure of the drawing represents an chamber by a conductive partition I6 I. . Coupling ting cathode 9 which may be associated with any between the guide and the resonant chamber may suitable heating means energized, in the embodi ment illustrated, through leads I0 and II by a 50 be effected by means of a suitable aperture I62 in the partition I6I. The wave guide may be source I2 of electromotive force. Associated with formed as an extension of the Walls of the reso the cathode '9 there may be an electrode I3 for nator I2? as shown. _ use in regulating and varying the current of Separated from the gap I21 by a suitable drift the electron beam and commonly known as an ac celerating electrode. It may be adjacent to and 55 space I29 is a gap I30 which is de?ned by op coaxial with the cathode. ' A plurality of conductive discs H I to 2I'I, in—. elusive, are hermetically sealed into and through the envelope I in any known manner. The discs are spaced at suitable intervals along the path of 60 posed truncated conical portions of the discs 2I6 and 2H. These discs form portions of the walls of a resonator, e. g., a quarter wave-length co axial conductor system 2E8, which may have a tuning branch 209. A source It!) of alternat 2,410,841 3 4 ing potentials is connected with the electrode I24, 4 shown a precise or ?ne tuning arrangement, com the direct potential of electrode I24 being main prising a branch cavity 202 of relatively small tained at a relatively low potential with respect dimensions, shown broken open, in which is slid to the cathode by a source I4I, whereas the con ably mounted a piston I53 which may be moved ductice portions of the resonators I20, I28 and 208 5 by means of a suitably connected knob I54. A and the collector 3 are maintained at a relatively similar arrangement may be employed in con high positive potential with respect to the cath nection with the resonator I20. The branch ode by means of batteries 200 and 20I. The elec cavity 202 is preferably of such restricted dimen sions compared with the‘ main cavity that the trode I3 may be connected, as shown, to the positive terminal of the battery 200. To effect resonant frequency of the main cavity is close to the relative potential values hereinbefore speci and somewhat below the range of free transmis ?ed the potential of the battery I4I may be sion of the branch cavity so that the latter will relatively low with respect to the combined po not fully support a wave of the frequency to be tential of batteries 200 and 20I. The tuning resonated. Then a relatively large motion of the branch 209 may serve to de?ne the short-cir 15 piston I53 will produce only a relatively small change in the resonant frequency of the combi cuited end or voltage node of the quarter wave length line 208, another branch 2I0 being pro nation. The currents ?owing in the branch cav vided for connection to any suitable load. ity will be less than in the main cavity with the In the operation of the system shown in the result that any losses associated with the slid drawing, the input wave, the carrier frequency 20 ing contacts between the piston I53 and the walls of the cavity 202 will be minimized. of which will be designated f1 and which wave The resonator I20 is provided with adjustable may bear signals in the form of modulations, side cavities 203 and 204 for the purpose of en e. g., amplitude modulations, is resonated in the chamber I20 and produces an electron velocity abling the resonator to respond to a relatively variation in the electron stream as the latter wide frequency band. The side cavity 203 is traverses the associated gap I2I. The frequency coupled to the main cavity by means of an aper ture 205 and is adjustable by means of a piston of the wave supplied by the local source I40 will be designated f2. Electron velocity sorting takes 206 connected to a knob 201. The side cavity 204 is connected to the main cavity and adjustable in place within the tube I22 due to the influence of the relatively low potential of the electrode I24. 30 a similar manner. The resonator I28 may be With proper selection or adjustment of the bat similarly equipped. The aperture 205 is prefer tery potentials, a condition is readily secured ably of a suitable size to provide a loose coupling in which the faster electrons pass through the between the adjacent chambers. The side cav space within the electrodes I24 and I26 whereas ities may be independently adjusted to resonate the slower electrons are de?ected and intercepted at the same frequency as the associated main cav ity or at slightly different frequencies, producing by the electrodes I22, I24 and I26, the result being a charge density variation both in the in either case a broad frequency band or rela stream of electrons which pass beyond the tube tively ?at transmission characteristic in the well I25 and in the current intercepted by the elec known manner of coupled resonant circuits of trodes. The degree of velocity sorting and re 40 Whatever form. sultant grouping produced is, however, in the In the operation of the system as above de present system, under the control of the local scribed the resonator I20 is assumed broadly source I40 by virtue of the variable potential tuned to the'frequency ii of the incoming wave superimposed upon the direct current biasing po and responsive to the sidebands due to the modu tential of the electrode I24 which causes the re- ' sultant, bias to ?uctuate. Upon passing the gap I21, the density-varied electron stream serves to excite electromagnetic oscillations in the reso nator I28, which resonator may be tuned to re spond to one or both of the frequencies ‘ (f1+f2) and (ii-f2), to reinforce these frequen cies which, it will be noted, are modulation prod ucts separated from the frequency of resonator I20 by an amount equal to the value of the fre quency of the source I40. Oscillations thus pr'o- ’ duced in ‘resonator I28 impress a corresponding velocity variation upon the electron stream as the latter traverses the gap I21. The velocity varia tion of the electron stream entering the drift space I29 will contain a component of the local lation which the incoming wave may bear. The resonator I28 may be tuned broadly to (f1+f2) or (f1—f2) as desired, while the line 208 is tuned to is. It is also feasible to operate by tuning the res onator I28 sharply to one of the above-mentioned frequencies. In that case, the side chambers 203’ and 204' are not needed and the apertures for coupling the side chambers to the main cavity should be closed. It is also feasible to operate with the resonator I 28 tuned so broadly as to include both (f1+f2) and (fi-fz), in which case the line 208 may be energized at twice the fre quency f2 and the length of the line 208 up to the position of the tuning stub should be increased accordingly. What is claimed is: A tuning arrangement comprising a substan tially closed system of resonating chambers con frequency is of source I 40 bearing the signal modulations of the original incoming Wave of frequency ii. The velocity variation is con taining a main chamber and a communicating verted in the drift space I29 into density varia branch chamber, said branch chamber being of tions at the gap I30 by the grouping effect of ' : restricted faster electrons overtaking slower electrons. The resonant line 208 may be tuned by means of the adjustable branch 209 to the frequency is of the source I40 and will be excited into forced oscillations by means of the density variations at the gap I30. The output of the line 208 may be led through the branch 2I0 to a suitable load such as an intermediate frequency ampli?er or other utilization means. In connection with the resonator [28 there is dimensions to determine for said branch chamber a cut-off frequency close to and somewhat above the resonant frequency of the main chamber, whereby a Wave impressed upon said main chamber and substantially resonant therein is attenuated upon entering said branch chamber, and means for tuning said branch chamber to effect a ?ne tuning adjustment of the system as a whole. - ARTHUR L. SAMUEL. '