US2496378A

US2496378A - Cavity resonator device for ultra-short waves

Info

Publication number: US2496378A
Application number: US664498A
Authority: US
Inventors: Coeterier Frederik
Original assignee: Hartford National Bank and Trust Co
Current assignee: Hartford National Bank and Trust Co
Priority date: 1942-06-27
Filing date: 1946-04-24
Publication date: 1950-02-07
Anticipated expiration: 1967-02-07
Also published as: BE451255A

Description

F. coETERlE 2,496,378

CVITY RESONATOR DEVICE FOR ULTRA-SHORT WAVES Feb. 7, 1950 Filed April 24, 1946 FZZEERIK COEJERIER.

INVENToR.

ATTORNEY.

Patented Feb. 7, 1950 ULTRA- SHORT WAVES Frederik Coeterier, Eindhoven, Netherlands, as-

signor, by mesne assignments, to Hartford National Bank and Trust Company, Hartford,

Conn., as trustee Application April 24, 1946, Serial No. 664,498 In the Netherlands une 27, 1942 section 1, Public Law 69o, August 8,1946 Patent expires June 27, 1962 12 claims. (ci. 315-6) This invention relates to a resonator, particularly a cavity resonator, and a device comprisingv such a cavity resonator.

The term cavity resonator is to be understood here and hereinafter to mean an oscillatory circuit for ultra-short waves constituted as a cavity resonator in which a concentrated inductance and capacity are missing and the dimensions of which are hence of the order of magnitude .of the wavelength of the fundamental frequency (smallest natural frequency). As set out more fully for example in Philips Technisch Tijdschrift, July 1941, pages 222, 223 the said reso--V nators are among the non-quasi-stationary sys ems. Y

The wall of a cavity resonator constitutes a body closed on all sides except, asis well-known, for the apertures which have to be formed in the wall, for example for the wired electrical connection to the inside of the wall or for the introduc. tion of coupling loops. v-

In addition, devices for ultra-short waves are known in which use is made of a discharge tube which is provided with means for the generation of an electron beam and in which the electron beam passes through the bore of a cavityl constructed as a cavity resonator.

The apertures formed in the wall of the reso,r nator, particularly if their dimensions are no longer small compared with the Wavelength, bring about considerable lowering of the quality of the cavity resonator.

The invention has for its object to provide means for limiting this loss in quality while conserving the accessibility of the aperture with a cavity resonator.

According to the invention,for this purpose the path followed by a loss current emerging over the edge of the aperture has connected in series therewith a. secondary cavity resonator provided with a. bore and preferably constructed as a cavity resonator which has a natural frequency that corresponds with a natural frequency of the pri. mary resonator and which is so arranged that the aperture is in line with the bore. l

The measure according to theinventionhas the eil'ect of introducing a high resistance, that is the resonance resistance of'the 4secondary resonator, into the loss current path, with the result that the loss current is limited.

In order that the invention may be clearly understood and readily carried into eiect it will now be described more fully with reference to the accompanying drawing, in which Fig. 1 is a known cavity resonator.

Fig. 2 shows a cavity resonator according to the invention having il-at secondary cavity resonator.

Fig. 3 shows a cavity resonator according to the invention comprising secondary cavity resonators each of which is constituted by two conis rotation-symmetrical with respect to the axis 2 vhas apertures 4, 4' formed in its .wall 3. On excitation of the cavity resonator for example by means of a loop-like conductor 5, the edge of the' aperture 4, which edge is located in a potential antinode, will be at a high-frequency voltage relatively to the surroundings. Due to this, other parts of the external surface of the cavity resonator will also be at high-frequency voltage relatively to the surroundings and, since the outer wall, as denoted in the figure by l and 1', must be regarded as earthed by capacitative agency, a considerable loss current ensues. This loss current, which emerges over the edge 6 of the aperture, followsthe path shown in dotted lines in the ngure and is responsible for considerable lowering in quality of the cavity resonator.

According to the invention, this loss of quality is limited by the use of secondary cavity resonators, 8, 8' arranged in the manner shown in Fig. 2 so that the said loss current is con ducted via one of these secondary resonators. The latter are bored at 4, 9 and 4', 9' so that the apertures 4 and 4' of the primary cavity resonator continue accessible. The resonance resistance occurring between the ends 4 and 9 of the secondary cavity resonator 8 is thus inserted in the loss current. In the case of lossfree construction of the cavity resonator 8 this introduces substantial suppression of the loss current since due to the potential distribution now occurring in the loss current path the edges l0 and l0' of the

secondary cavity resonators

8 and 8 respectively and thus the outside of all cavity resonators will be substantially at earth potential and hence the capacity (l, 1') will have no longer any harmful eect as regards the surrounding.

If, as hitherto taken for granted, the primary cavity resonator is not excited in its fundamental frequency but in one of the higher natural frequencies, the secondary cavity resonators must obviously be tuned to this higher natural frequency. According to circumstances, it may be advantageous to cause the fundamental frequency of the secondary cavity resonator to correspond nally with with a higher natural frequency of the primary cavity resonator since the required space is thus limited. For the purpose of limiting the accuracy requirements as to the dimensions cf the cavity resonators from a mechanical point of view 1 and also for compensating circuit capacities or l the like it is desirable that use should be made of means for adjusting the natural frequencies of the secondary cavity resonators, for example a member formed of insulating-material or a conductor may for this purpose'be arrangedl in the` cavity resonator concerned.

In the form of construction vshown inFig. 2A radiation losses occur through the apertures 9, 9' of the secondary cavity resonators S, 8 as

origiapertures

4, 4. reduced by constituting the secondary cavity resonators, as shown in Fig. -3, by two concentric hollow com'iuctorsl II, ,I2 and II', I2 respectively united at corresponding, ends, the internal condctors I2, I2' comprising'an interruption I3, I3 immediately adjacent the

apertures

4, 4.

` lIf desired, adjoining cavity resonators may in this case have a common wall part, as in Fig. 2. The invention may be used with particularladvantage with devioesfor ultra-short wavesf` in which use is made ofA la discharge tube comprising means for generating an electron beam and the electron beam traverses the bore oi a cavity resonator, yeither for vthe/purpose of modulatingv the speed ofthe electron beainor to derive energy from the intensitymodulated beam. In such devices it is' often desirable or even necessary that the bore of the cavity resonator should be made comparativelyl large, it being so large that particularly with veryshortwaves the dimensions of the apertures. made in the cavity resonator are no longer, small compared with the operating wavelength, this e'ntailing great losses.

Fig. 4 shows such a device for generating ultrashort waves towhich the invention is applied;

A discharge tube I4 has arranged in it on the one side an electrode system I5 for generating the electron beam4 and on the other a collector electrode I6.

In between are arranged two mutually coupled primary cavity resonators i1 and IB respectively. The cavity resonator I'I serves for the velocity modulation of the electron beam. In the space intermediate the two cavity resonators this velocity modulation is converted into an intensity -modulation so that the cavity resonator I8 permits'ofderiving energy from the beam.

j For the purpose of improving the quality of the primary cavity resonators I1 and I8 provision is made of secondary cavity resonators I9, I9' and 20, serving solely for this purpose and conlstituted essentially, by two concentric, hollow conductors Whose interrupted internal conductors are aligned with the bores of the primary cavity resonators so that the electron beam can pass without any obstruction. If desired, the secondary cavity resonator maybe arranged, as distinguished from the embodiment illustrated, entirely'outside the surrounding envelope of the discharge tube.

In'thisconstruction, the cavity resonators I1 and I9 are not arranged in direct contact with each other but ata small distance and are interconnected by a metal tube piece 2I in order that it ,may bepossible for a concentration coil 22 to be arrangedin the spaceA thus obtained between the said cavity resonators.

In' the embodiments shown the primary cavity the cavity resonator I through the The said radiation losses can be consequently does not constitute a bore or else one or more apertures not arranged at the area of apotential'antinode and also in ,the case of the primary cavity resonator having lfor example a4 concentrated capacity.

Lastly, the secondary cavity resonator may have a.,concentratedA capacity and/or induotance in orderto'limitcthe. required space in so far as is permittedby the quality improvement aimed at of theprimaryhollow space resonator.

It is to be understood that the invention is not limited'to. those'specific embodiments herein described, but that various modifications will occur to vthose skilled in the art without departing from the spirit and the scope-of the invention.

l. Al cavity resonator system comprising a rst cavity resonator and a second 'cavity resonatorhaving a resonant frequency coi-responding to thev resonant frequency of said firstv resonator"I saidv resonators having contiguous wall portions pro'- vided withcoincident aperturesjthe diameter of said apertures being less than fthe' Aaxial dimension of said-iirst cavity resonator',ahd'said second resonator beingA` provided in lanotherwall'portion thereof with-a; second-'aperture vinline with said rstapertures. if "f 2.' A cavity resonator system comprisinga pri*- mary cavityresonator-havinglawall portion provided with -an aperturewliose Vdiameter isless than the axial dimension of said primary reso'- nator, and4 means -t'o` reduce electrical 'losses oc-I curring at saidaperture, 'svaidrnans comprising; a secondary-cavity' resonator 4having a resonant frequency corresponding 'to theres'onant frequency of saidprima-ry resonatorfawall portion contiguous to said first wall'portion a'nd provided with an aperture coincident with said aperture of said first lwall portionjand-"a" second walt-pori tion provided with'an aperture 'in 1lin'e with the apertures in saidV contiguous wall portions. f

3. A cavity resonatorsysterncoinprising apr'ii'- mary cavity resonator-having a wall portion' provided with'an aperture whose `dian'leter is smaller than the axial dimension of said-"primary'reso-I nator, and means to reduce' electrical losses occurring at'said aperture,v said meansfcomprising a secondary cavity resonator having a resonant frequency corresponding to the v 'resonant frequencyof said primary resonator, a wall portion includingsaidaperture in common withv said fpri'# mary resonator, and asecond wall `portion pro` rtriuded with Van aperture in linewitli said iirst'aper- 4. A cavity resonator system `comprising a primarycavity resonator havingspaced wall por tions each provided with an aperture, whose' diameter is small with respect to the spacing between -said wallv portions; and means'to reduce:- electrical losses occurring at said. apertures, 'said' means comprisin'ga rstisecondary cavity reso? nator: having awall portion contiguous to one. of 'said wall' portions` of said'primary resonator. and provided with arr aperture coincident with the-aperture of said wall portion of said primaryj resonatorA and a second wall portion provided with an' aperture in linewith the apertures in said. contiguouswall' fportiruas, and a 'secondsecondari cavity resonator; having a wall portion contiguous4 to the other orsaidwailpprtionsonsaid.primary resonator ancifprovidedwith an aperture coincident with the aperture of said other of said Wall portions of said primary resonator and a second wall portion provided with an aperture in line with the apertures in said second contiguous Wall portions, said rst and said second secondary resonators having a resonant frequency corresponding to the resonant frequency of said primary resonator.

5. A cavity resonator system comprising a primary cavity resonator having spaced wall portions each provided with an aperture having a diameter which is small with respect to the spacing between said wall portions, and two secondary cavity resonators each positioned adjacent to one of said wall portions, said secondary resonators each having a rst wall portion contiguous to said wall portions of said primary resonator and provided with an aperture coincident with said aperture of said contiguous wall portion and a second wall portion provided with an aperture in line with said apertures of said contiguous wall portions, each of said secondary resonators having a resonant frequency corresponding to the resonant frequency of said primary resonator.

6. A cavity resonator system comprising a primary cavity resonator having spaced wall portions each provided with an aperture having a diameter which is small with respect to the spacing between said wall portions, and two secondary cavity resonators each positioned adjacent to one of said wall portions, said secondary resonators each having a irst wall portion contiguous to said wall portions of said primary resonator and provided with an aperture'coincident with said aperture of said contiguous wall portions and a second wall portion comprising a tubular member extending within said second secondary resonator, said tubular member being provided with a bore an axis of which is coincident with the axis of the apertures of said contiguous wall portions, and said secondary resonators having a resonant frequency corresponding to the resonant frequency of said primary resonator.

7. A cavity resonator system comprising a primary cavity resonator having spaced wall portions each provided with an aperture having a diameter which is small with respect to the spacing between said wall portions, and two secondary cavity resonators each positioned adjacent to one of said wall portions each of said secondary resonators having a first wall portion contiguous to one of said wall portions of said primary resonator and provided with an aperture coincident With said aperture of said contiguous Wall portions and a second wall portion, said second wall portion comprising a tubular member extending within said second secondary resonator to an antinode potential region and provided with a bore an axis of which is coincident with the axis of the apertures of said contiguous wall portions, said secondary resonators having a resonant frequency corresponding to the resonant frequency of said primary resonator.

8. A cavity resonator system comprising a primary cavity resonator having spaced wall portions each provided with an aperture having a diameter which is small with respect to the spacing between said wall portions, and two secondary cavity resonators each having a wall portion including said aperture in common with said primary resonator, each of said secondary resonators comprising two concentric conductors the axes of which are coincident with the axis of said apertures of said common wall portions, and means interconnecting said conductors at the ends thereof remote from saidy common wall por-l tions said secondary resonators having a resonant frequency corresponding to the resonant frequency of said primary resonator.

9. A cavity resonator system comprising a primary cavity resonator having spaced wall portions each provided with an aperture having a diameter which is small with respect to the spacing between said Wall portions, and two second--v ary cavity resonators each having a wall portion including said aperture in common with said resonator, each of said secondary resonators comprising two concentric conductors, the axes of which are coincident with the' axis of said apertures of said common wall portions, and means interconnecting said conductors at the ends thereof remote from said common wall portions, the inner conductor of said conductors ter-z minating at an antinode potential region in the secondary resonator, said secondary resonators having a resonant frequency corresponding to. the resonant frequency of said. primary resonator.

10. A cavity resonator system comprising a primary resonator having spaced wall portions each provided with an aperture having a diameter which is small with respect tothe spacing between said wall portions, and two secondary cavity resonators each having a wall portion including said aperture in common with said primary resonator, each of said secondary resonators comprising two concentric cylindrical conductors the axes of which are coincident with the axis of said apertures of said common wall portions, and a `disc member interconnectingv said conductors at the ends thereof remote from the common wall portion, said secondary reso'- nators having a resonant frequency corresponding to the resonant frequency of said primary resonator.

11. A cavity resonator system comprising a rst group of cavity resonator elements, a second group of cavity resonator elements spaced from and axially aligned with said rst group, each of said groups comprising primary cavity resonator having spaced wall portions each provided with an aperture, and a first secondary cavity resonator each having a wall portion including said aperture in common with said primary resonator and comprising two concentric tubular conductors the axes of each are coincident with an axis of said aperture of said common Wall portions and means interconnecting said conductors at the ends thereof remote from said common wall portions, said first group of cavity resonators further comprising a concentrator solenoid positioned adjacent to said primary resonator, and a second secondary cavity resonator comprising a wall portion positioned adjacent to said solenoid and provided with an aperture axially aligned with the apertures of 60 the primary cavity resonator, said second secondary resonator further comprising two concentric tubular conductors the axes of which are coincident with the axis of said apertures of said common wall portions and means interconnecting 65 said conductors at the ends thereof remote from said common wall portions, a tubular conducting member interposed between said primary resonator and said second secondary resonator and through said solenoid said second group of cavity 7o resonators comprising a second secondary cavity resonator comprising two concentric tubular conductors the axes of which are coincident with the axis of said aperture of said common wall portions and means interconnecting said conductors 75 at the ends thereof remote from said common andere wall portions; theinner conductor of saidisecondary Ycavity resonators 4extending within the resonator to anantinode potential region, means electrically coupling the'primary cavity resonators of each of said groups,the resonant frequency of the resonator of said first group corresponding to the resonant frequency of the resonator of said second group, and the resonant frequency of said secondary resonatorsof each of said groups corresponding to the resonant frequency of the primary resonator of said groups.

12. A cavity resonator .system comprising a first group of cavity resonator elements, a second group of cavity resonator elements spaced from and axially aligned with said rst group, each of said groups comprising primary cavity resonator having spaced wall portions each provided with an aperture and a rst Secondary cavity resonator each having a wall portion including said aperture in common with said primary resonator and comprising two concentric tubular conductors the axes of each are coincident with the axis of said aperture of said common wall portions and means interconnecting said conductors at the ends thereof remote from said common wall portions, said rst group of cavity resonators further comprising a concentrator solenoid positioned adjacent to said primary resonator, and a second secondary cavity resonator comprising a wall portion positioned adjacent to said solenoid and provided with an aperture axially aligned with the apertures of the primary cavity resonator, said second secondary resonator further comprising two concentric tubular conductors the axes of which are coincident with the-axis of said apertures of said common wall portions and means interconnecting said conductors at the ends thereof remote from said common wall portions, a tubular conducting member interposed between said primary resonator andsaid second secondary resonatorand through said solenoid, said second group of cavity resonators comprising a second secondary cavityresonator comprising two concentric tubular conductors the axes of which are coincident with the axis of said aperture of said common wall portions and means interconnecting said conductors at the ends thereof remote from said common Wall portions, the inner con-` ductor of said secondary cavity resonators extending within the resonator to an antinode potential region, means electrically coupling the primary cavity resonators of each of said groups, the resonant frequency of the resonator of said iirst group corresponding to the resonant frequency of the resonator ofsaid second group, the resonant frequency of said secondary resonators of each of said groups corresponding to the resonant frequency of the primary resonator of said groups, means to generate an electron beam axially aligned with and arranged on the side of said first group of cavity resonator elements remote from said concentrator solenoid, focusing means interposed between said generator means and said side of said rst group to traject said beam into the apertures of said groups of cavity resonator elements and means to collect electrons from said beam axially aligned and :arranged at the end of said groups remote from said generator means.

FREDERIK COETERIER.

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

UNITED STATES PATENTS Number Name Date 2,242,275 Varian May 20, 1941 2,263,648 Salzberg Nov. 25, 1941 2,280,824 Hansen et a1 Apr. 28, 1942 2,323,729 Ryan July 6, 1943 2,391,016 Ginzton et al Dec. 18, 1945 2,403,795 Hahn July 9, 1946 2,409,179 Anderson Oct. 15, 1946