US2521719A - High-frequency electron discharge apparatus frequency control - Google Patents

Description

Sept' 12, 1950 L. R. HILDEBRAND 2,521,719

HIGH-FREQUENCY ELECTRON DISCHARGE APPARATUS FREQUENCY CONTROL Filed March 14, 1944 2 Sheets-Sheet 2 gli i 36 24 l s L INVENTOR LYNN R. HILDEBRAND yTTORNEY Patented Sept. 12, 1950 HIGH-FREQUENCY ELECTRON DISCHARGE APPARATUS FREQUENCY CONTR/OL Lynn R. Hildebrand, Hempstead, N. Y., assigner to The Sperry Corporation, a corporation of Delaware Application March 14, 1944, Serial No. 526,455

18 Claims.

This invention relates to electron discharge hollow resonator apparatus and more particularly to thermally responsive frequency control arrangements for such apparatus.

According to the invention, exceptionally speedy frequency control of a hollow resonator device is accomplished by providing within an evacuated envelope containing the resonator a plurality of thermally sensitive 4and electrically controlled members which act independently to vary the resonator frequency in opposite directions. Also a special resonator frequency adjustment operated by a manual control externally of the envelope is provided for obtaining frequency regulation independently of energization of the thermally responsive members.

It is therefore a major object of the invention to provide a hollow resonator electron discharge device having novel thermally sensitive frequency control arrangements.

Another object of the invention is to provide a cavity resonator electron discharge device having novel electrical frequency control arrangements.

A further object of the invention is to provide a novel compact and efficient association of hollow resonator and associated frequency control elements within an evacuated envelope.

It is a further object of the invention to provide a novel electron discharge hollow resonator device having special electrically controlled thermally sensitive means Within van evacuated envelope containing the resonator for independently varying the resonator frequency in opposite directions, and associated externally accessible manual frequency control means for preselecting a reference frequency condition independently of energization of said thermally responsive means.

A further object, of the invention is to provide -a novel manually operable external frequency control for varying the frequency of a hollow resonator mounted within an evacuated envelope.

It is a further object of the invention to provide novel cavity resonator electron discharge tube structure.

Further objects of the invention will presently appear as the description proceeds in connection with the appended claims and the annexed drawings wherein:

Fig. 1 is an elevation partly in section illustrating frequency control mechanism of a hollow resonator device according to a preferred embodiment of the invention viewed along line l-l of Fia B;

Fig. 2 is an elevation partly in section of a portion of the frequency control mechanism of Fig. l as viewed at about right angles to the showing in Fig. l and along line 2-2 of Fig. 3;

Fig. 3 is -a section in plan along line 3--3 of Fig. 1;

Fig. 4 is a fragmentary elevation partly in section illustrating a further embodiment of thermally responsive frequency control structure which may be employed in lieu of that of Figs. l and 2, viewed along line ll-ll of Fig. 5;

Fig. 5 is a section in plan taken along line 5-5 of Fig. 4;

Fig. 64 is a fragmentary elevation partly in section illustrating the frequency control mechanism of Fig. 4 as viewed at about right angles to the showing in, Fig. 4, along line 6-6 of Fig. 5.

Referring now to Figs. 1 to 3, a cylindrical envelope ll, which may be of metal, is secured aS by a vacuum tight jointindicated at I2 to a pronged base i3 of the usual vacuum tube type. A base structure lll is rigidly fixed to envelope Il and base i3. Passing through base structure l are the lead-in connections, one of which is shown at 5. Connection 5 is sealed into base structure l0 by a suitable insulating seal 6. To prevent strains from being transmitted to seal 6, connection 5 is formed with recesses l at either side of seal 6, providing reduced diameter bending sections. This permits ready slight bending of connection 6, should that be necessary, as for connecting to prong 8, and also prevents strain by expansion of rigid connections such as 9.

A plurality of spaced posts lli and I5 upstanding from the base structure lil within envelope l I rigidly carry an insulating support member I6 on which is mounted a suitable cathode or electron gun or electron emitter assembly Il for projecting a stream of electrons coaxial with envelope Il.

A further plurality of spaced posts, two of which are illustrated at IS in Figure 2, also upstand rigidly from the base structure Il). Preferably three equally circumferentially spaced posts i8 are provided, and the upper end of each such post is reduced at i9 to extend through a suitable aperture in an annular resonator support 2 l. Beyond support or ring 2 l, each reduced post end i9 is threaded as at I9 to t into a tapped axial bore at the lower end of a short post 22 so that support 2l is rigidly clamped between posts I8 and 22. The upper end 23 of each post` 22 is reduced at 23 to extend through a suitable aperture in a second annular support member 2t, and threaded for receiving a nut 25 whereby 3 support member or ring 24 is fixed to the top ends of post 22.

Posts I8 and 22 and support members 2l and 24 thus provide a sturdy non-microphonic frame upstanding from the base, and substantially all the parts within envelope l, except the reilector to be described, are mounted on this frame. Annular members 2| and 24 are parallel to each other, and preferably coaxial with the electron stream from cathode Il.

A flat shallow cylindrical hollow or cavity resonator member 25 is xed to support ring 2|, as by soldering its peripheral side wall 2l directly to the annular internal surface of support ring 2|. Resonator 26 is thereby mounted on ring 2| with its axis coincident with that of the electron stream.

Opposite resonator end walls 2S and 29 are flexible, preferably comprising generally parallel, annularly crimped, integral radially inward extensions of side wall 2. Walls 28 and 29 are of resilient highly conductive material, such as beryllium copper, phosphor bronze, other copperplated metals or even copper itself, so as to be suiciently resilient to tend to retain its illustrat'ed preformed shape against small displacements, a useful property in the invention, as will appear.

Walls 28 and 29 are centrally apertured in alignment, and the aperture in lower wall 28 has secured thereto a small collar insert 3| on which is mounted a wire mesh or other form of grid 32. Similarly a collar 33 secured Within the aperture in upper wall 29 has secured thereto a second similar grid 35. Grids 32 and 3d are portions of two similar translated spheres and coaxial with the electron stream, and are thus prebowed so as tov prevent undesired distortion by buckling when heated by electron impact.

A centrally apertured radially extending plate 35 has its inner periphery suitably clamped by collar 33 to the central region of upper resonator wall 29. An inverted U-shaped bracket Sil has the ends of its depending legs fixed as by welding to plate 35. Bracket 38 is resiliently connected to support ring 24;. as by a pliuality of radially extending spring levers 3l having their outer. ends staked c-r similarly fixed to ring 24 (Fig. 3) and their inner ends slidably projecting through suitable parallel longitudinal slots 38 formed in a small tubular collar 39 rigid with the bridge of bracket 35. Each spring lever 31 is preferably formed with an intermediate coil fil so as to increase its effective lengthand strength.

Spring levers 3'! combine to urge bracket 36 downwardly, thereby tending to urge grid 3i! toward grid 32. This downward displacement of grid 34 is resisted by the resiliency of wall 29 and also by a pair of thermally-extensible flexible wires or strips 4-2 which have their lower ends anchored to plate 35 as at 43 (Fig. 2) and their upper ends welded or similarly xed to opposite ends of a short conductor bar 44 centrally imbedded in an insulating body 45 of glass or the like.

A tension spring 46 is connected at its lower end to an eye member 4l rigid with glass body 45 and at its upper end to a suitable pin 48 rigid with the bridge of an elongated bifurcated support 49 which has the lower ends of its arms secured to ring 2.6i as by nut 2E and machine screw l.

A second conductor bar 52 centrally imbedded in glass body 65 has its opposite ends welded to 4 the upper ends of a second pair of thermally responsive flexible wires or strips 53 which have their lower ends anchored to ring 2|, as by suitable terminals clamped at 5!! between post 22 and ring .l and at 55 by machine screw 5S (Fig. 2).

Referring again to Fig. l, a centrally apertured plate 5'! has its inner periphery clamped by collar 3| to the central region ol lower resonator wall 28. At diam'etrically opposite regions, plate 5l has riveted thereto the lower ends of upstanding push rods 5B and 59 which extend freely through suitable apertures in rings 2l and 2f; and have their upper ends similarly riveted to the lower terminals of the diverging arms of a second bifurcated support 6| disposed in a plane perpendicular to that of support 49. Supports 49 and 6| are arranged in substantially nested relation for economy in space and material.

A compression spring 52 is interposed between the adjacent bridge portions of supports 49 and 5|, and' reacts against support lltv to urge support 6| upwardly. Thus spring 52 tends to urge grid 32 toward grid 34.

Upward displacement of support 6| is opposed and controlled by externally accessible manually adjustable arrangements. The upper end of envelope is sealed vacuum tight by a flexible diaphragm 63 which may be an annularly crimped disc (preferably steel for greater ilexibility and longer life before mechanical rupture) similar to walls 28 and 29. Diaphragm 93 carries a central button GG having a recessed lower face 64 within envelope adapted to t with an upstanding conical seat 65 on the bridge of support (il.

Externally of envelope Il, button E4 carries a rigid upstanding threaded post 6G which may be integral with button till if desired. A rigid end closure member 61 protectively encloses the end of envelope ll beyond diaphragm G3, and the shank S8 of an external manual control knob 59 is rotatably mounted on closure member 6l. Shank 58 has an internal threaded bore fitting with post 6E and is held against axial displacement when rotated. Hence, when knob 69 is rotated, button 64 is positively axially displaced relative to envelope and this motion is positively transmitted within envelope I by support di', push rods 58, 59, and plate 5l to displace grid 32 toward or away from grid 34'. Closure 6l is formed with an air escape aperture 7| to permit this adjustment.

The above manual adjustment is made independently of any other frequency control provision. A differential screw arrangement may be used here to gain ner control.

A suitable arcuate metal reflector electrode l2 is rigidly mounted within envelope in axial alignment with the electron stream emerging through grid 3d. Reflector I2 is xed to an insulation disc 73 secured as by a sheetI metal rim 'M upon a support plate 'l5 which extends through the space within bracket t6 and is secured as by fastening elements 'I8 upon the upper ends of a pair of posts '11 upstanding from the base structure Ill. A suitable potential is applied to reflector l2, as by lead 78.

The various elements adapted for electrical energization within envelope are suitably connected to base prongs, and these connections are not shown since their details do not comprise part of the present invention. A suitable coaxial line 'E9 coupled to the resonator field by a loop 8| extends through the base in vacuum tight relation and enables extraction of high frequency energy from resonator 26.

In operation, with wires 42 and 53 de-energized, the gap between grids 32 and 34 may be varied micrometrically by manipulation of knob 69 to preset the natural frequency of the resonator at an operating point from which the thermally sensitive wires 42 and 53 may be selectively effective to change the resonator frequency in opposite directions, as will appear. Compression spring 62 insures that this adjustment has no mechanical play or lost motion.

Assume that wires 42, which are electrically and mechanically in parallel for uniformly distributing the frequency control forces, are heated by passage of current therethrough while wires 53 remain unenergized. Wires 42 elongate, thereby permitting radial springs 37 to displace grid 34 against the resistance of flexible wall 29 to decrease the gap between grids 32 and 34 and thus decrease the resonant frequency of resonator 26, with a corresponding change in output frequency of the device. During this action glass body 45 is held against displacement due to wires 53 which oppose the pull of spring 46, so that the upper ends of wires 42 are effectively stationary.

A decrease in energization of wires 42 will permit them to contract and thus will cause grid 34 to move away from grid 32, thereby increasing the resonant frequency of the resonator 26. This type of action is used in prior devices, but has several disadvantages. Firstly, it is necessary to maintain the thermal wires at half energization, when at normal or mid-frequency, in order to be able to tune in both directions by increase or decrease of their excitation. This causes an undesirable continuous power drain, and also renders the device sensitive to changes in ambient temperature, since the length of the thermal Wires depends on their temperature, which in turn depends on their power dissipation and thus on the ambient temperature.

A further and more serious disadvantage resides in the fact that unequal rates of tuning are obtained in the two directions. Tuning .by increasing excitation is quite fast, as is desirable in such uses as automatic frequency control Where it provides a sensitive and accurate frequency adjustment without substantial overshooting of the final desired frequency. However, tuning by decreasing excitation is relatively slow with corresponding disadvantages.

These disadvantages of the prior devices are substantially overcome by the present invention, in which, as will be seen, tuning in both directions is effected by increase in thermal wire excitation. Thus, assume that wires 53, which are also electrically and mechanically in parallel, are heated by passage of electric current therethrough while wires 42 remain iixedly energized. Wires 53 elongate, thereby permitting tension spring 46 to displace glass body 45 upwardly. This motion is transmitted through wires 42 and plate 35 to increase the gap between grids 32 and 34 and thus increase the frequency of resonator 26.

Any suitable electrical circuit connected to the socket into which the base prongs are inserted can be employed to selectively pass current through either of the conductor pairs 42 or 53, or to energize one more than the other as desired. No illustration of such circuits is here necessary to understand the present invention which concerns improved frequency control and other 'structural features of the hollow resonator device.

Thus, after the operating frequency point of the resonator has been mechanically preset, manual or automatic selective energization of the thermally sensitive wire pairs 42 or 53 may be utilized for quickly varying the resonator frequency within an appreciable range. The use of pairs of symmetrically disposed wires 42 and 53 insures that relative displacement of grids 32 and 34 is substantially parallel which is helpful to reliable frequency control.

The invention enables a saving in power over prior thermal tuning employing single directional tuning with one or more wires or struts which must be kept energized to substantially half normal full elongation in order to maintain the desired operating point, since in the present invention both wires are normally unenergized, and the normal frequency is set manually.

Also, better temperatinre stability is mentioned, since any change in normal temperature of wires cl2 is accomplished by a corresponding change for wires 53. Thus wires 42 and 53 extend substantially equally, resulting in no frequency change.

It will be noted that in the embodiment discussed above with respect to Figs. 1-3, the thermal tuning wires 42 and 53 act to change the tuning in respective dierent directions while actuating the same grid 34 of resonator 26, and the mechanical tuning by control 65 operates only on the other grid 32 of resonator 26. The modification illustrated in Figs. 4-6, on the other hand, utilizes respective different grids for thermally tuning in respective directions and has the mechanical or manual tuning control operative together with one of the thermal controls upon one grid, but independently thereof.

Thus, referring to Figs. 4 6, elements corresponding to those of the prior figures are given the same reference character. In Figs. 4 6, the tuning wires 53 have been replaced by corresponding tuning wires 53', and a single tuning Wire 42', which may be also a rigid thermally f expansible strut where desired, replaces wires 42.

The support 43 of Figs. 1-3 has been replaced by a ring having a large internal opening :which is supported upon the rods 85, fixed to support 24. Ring 85 is thereby rigidly supported from the base. Ring 85 is preferably of insulating material and rigidly supports one end of each of the wires 53. These wires 53 extend freely through openings 9| and 92 in supports 24 and 2|, respectively, and are fixed at their ends ren mote from ring 85 to the conducting plate 57 which, in turn, is xed to the grid 32. In the present embodiment, plate 5'! is urged toward the lower support i6 by means of tension springs such as 93. Wires 53 have their upper ends suitably connected to an energization conductor 6I passing through one of the base prongs 6, as in the prior modifications. The lower ends of wires 53 are then grounded by connection to the plate 51 which supplies a ground return for the energizing current, so that wires 53' are electrically in parallel. It will be seen that by supplying suitable excitation to the wires 53', they will be caused to increase in length, permitting springs 93 to draw plate 5l and grid 32 downward and away from grid 34, whereby the resonant frequency of resonator 26 and consequently the out-y put frequency from the device is increased.

The thermal frequency control of the resonator in the opposite sense is entirely independent from that just described. Thus, the insulating bloc-k 45', corresponding to block 45 of preceding figures, is hung directly from the button 64 in diaphragm 63, as by means of the loop fl'l fixed to the block 45 and a loop S4 fixed to button 64, replacing the conical seat 54 of prior gures.

Thermal wire 42' is then rigidly fastened at one end to the insulating block 45. The other end of wire 42' is centrally xed to the bridge 3G which is rigidly connected vto the grid 34 through the plate 35 as in the prior figures. It will be seen that effectively the present modification merely has replaced the wires 42 of the prior gures which were connected to plate 35, with a single wire 42 connected to the bridge 35. The springs 3l again urge bridge 3E and grid 34 downwardly toward grid S2. The upper end of Wire 42 is again suitably connected to an energization lead and one ci the base pins. The lower end is grounded by connection to bridge 3B. Upon energization of wire 42', it will increase in length, permitting spring 31 to urge grid 34 toward grid 32 thereby decreasing the output frequency from the device. This is seen to be independent from the control of grid 32.

For manual control of the output frequency, it is merely necessary to actuate knob 69, which causes displacement of button til as discussed with respect to the prior figures. Wire 42 is now of xed length, so that any displacement of button 64 permits springs 31 to produce a, corro-- sponding displacement of bridge 35 and grid 3i. Springs 3l assure positive motion of grid 3Q in both directions without backlash. The remaining portions of the device of Figs. 3-6 are similar to those of the prior figures and need not be repeated in detail.

If desired, of course, wire 42 could be replaced by a rigid strut 4which is also thermally extensible in the same manner. When such a strut is used, its upper end may be connected to button 64 and then the springs E? may be eliminated, since positive action is obtained in both directions of motion. However, it is still preferable to utilize the spring 37 in this case, in order to overcome any slack in the threads of screw 6G and to help centralize the bridge 33 and grid 34.

Also, if desired, the upper end of wire 42 could be maintained fixed as by connection t0 a member rigid with supports Zfl and 2i. In such case, ring 85 would no longer be rigidly supported from 24, but would be supported from button G4. in this way, the manual control 59 would actuate grid 32 instead of grid 34 as illustrated in the drawings.

In referring to the change of the resonant frequency of resonator Z in one sense, it will be understood that such a change in frequency may involve either an increase or decrease of the resonant frequency oi resonator 2li. However, a change in the resonant frequency in an opposite sense implies that the frequency is changed in a direction opposite to that specified in connection with the frequency change in one sense. For instance, if the change of frequency in one sense is considered to be an increase of frequency, then a change of frequency in an opposite sense indi- Cates a decrease or" frequency.

Since many changes could be made in the above construction and many apparently widely dierent embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above descriy 'ion or sla in the accompanying dranings shall be inte ated as illustrative and nit in a limiting sense.

lill

What is claimed is:

1. High frequency apparatus comprising a hollow resonator mounted on a support and having two spaced wall portions each movable relative to said support, a manual control member, motion-transmitting means connecting said member with one of said wall portions, said motiontransmitting means comprising thermally extensible means to elongate upon electrical energizetion thereof to move one of said wall portions in a given direction, and further similar thermally extensible means operably connected to the other of said wall portions for selectively moving said other wall portion independently and in an opposite direction from the movement of said one wall portion produced by said first thermally extensible means upon the electrical energization of said further extensible means, whereby the frequency of said resonator may be independently varied in opposite directions by said two thermally extensible means and may be further adjusted by said manual member.

2. High frequency apparatus comprising a hollow resonator mounted on a support and having two spaced wall portions each movable relative to said support, a manual control member, motion-transmitting means connecting said member with one of said wall portions, said motion-transmitting means comprising thermally extensible means adapted to vary in length in response to varying electrical excitation thereof, and further similar thermally extensible means operably connected to the other of said Wall portions for selectively moving said other Wall portion independently and in an opposite direction from the movement of said one wall portion produced by said first thermally extensible means upon the electrical energization of said further extensible means, whereby the frequency of said resonator may be independently varied in opposite directions by said two thermally extensible means and may be further adjusted by said manual member, said last-named means including a manually actuatable control member external of said envelope, and motiontransmitting means connecting said member to one of Said walls, said motion-transmitting means including said thermally extensible means, whereby said one wall may be actuated selectively by said manual member or by energizing said thermally extensible means.

3. High frequency apparatus comprising a support, a hollow resonator mounted on said support having a first Wall portion movable for varying the oscillation frequency of said resonator, a mounting member disposed adjacent said support, first means including a rst flexible thermally sensitive expansible and contractibie member for increasing the frequency of said resonator upon energization of said iirst member, second means including a second flexible thermally sensitive expansible and contractible member for decreasing the frequency of said resonator upon energization of said second member, each of said members having one end anchored to said mounting member in electrically insulated relation, means connecting the other ends of said flexible members to said support and said first movable resonator wall portion respectively, means resiliently connecting said mounting means to said support for maintaining said flexible members taut; and manually operable means opor ily connected to very thc oscillation frequency ol said resonator independently of actuation ol' said thermally sensitive 9 means, said last-named means comprising a second movable wall portion on said resonator and a manually manipulatable device operably connected to said second wall portion; said second wall portion being spaced from said first wall portion.

4. High frequency apparatus comprising a support, a hollow resonator mounted on said support having rst and second spaced wall portions separately movable for independently varying the oscillation frequency of said resonator, a mounting member disposed adjacent said support, a pair of flexible thermally sensitive expansible and contractible members each having one end anchored to said mounting member in electrically insulated relation, means connecting the other ends of said flexible members to said support and said rst movable resonator wall portion respectively, means resiliently connecting said mounting means to said support for maintaining said flexible members taut, said members varying upon energization the fre quency of said resonator in opposite senses, manually operable means operably connected to said second wall portion to vary the oscillation frequency of said resonator independently of actuation of said thermally sensitive means, and a second pair of flexible thermally sensitive members each being electrically and mechanically in parallel with one of said rst pair.

5. High frequency apparatus Comprising a support, a hollow resonator `mounted on said support and having two spaced wall portions movable relative to said support, a body of in sulating material resiliently connected to said support, two thermally sensitive expansible and contractible flexible frequency control members having corresponding spaced ends secured to said insulating body, means securing the other ends of said flexible members to said support and one of said movable resonator wall portions respectively, one of said members varying upon energization the frequency of said resonator in a first direction, the other of said members varying upon energization the frequency of said resonator in a second direction, said second direction being opposite to that of said first direction, and means for independently moving the other of said resonator wall portions for effecting further frequency control of said resonator.

6. High frequency apparatus comprising an evacuated envelope, a support, a hollow resonator mounted on said support within said envelope and having two spaced wall portions each movable relative to said support, thermally sensitive means within said envelope operably connected to one of said wall portions for selectively oppositely moving upon energization said one wall portion for independently varying the resonator frequency in opposite directions, and externally accessible manually operable means on said envelope connected through said envelope to the other of said movable wall portions for further independently varying the resonator frequency.

'7. The apparatus defined in claim 6, wherein said thermally sensitive means comprises two independently energizable sets of expansible and contractible flexible conductors operably connected to said support and said one wall portion respectively at corresponding ends and having their other ends resiliently connected to said support.

8. High frequency electron discharge apparatus comprising an evacuated envelope, a conductive hollow resonator body within. said envelope and having independently movable, generally parallel end walls formed with aligned electron-permeable regions, means in said envelope for projecting an electron stream through said regions, and means including a pair of separately acting thermally actuatable longitudinally extensible members and motion transmitting means Within said envelope for independently displacing each of said regions with respect to said body, whereby the width 'of the gap between said regions may be varied to selectively vary the resonator frequency. v

9. Apparatus as in claim 8, wherein a manually actuatable means external of said envelope is provided for cooperating with said motion transmitting means for displacing one of said walls, and said extensible members are adapted to independently displace the'other of said walls.

10. High frequency apparatus comprising a support, a hollow resonator mounted on said support and having two spaced wall portions each movable relative to said support, and a pair of thermally sensitive independently actuatable means for selectively independently moving saidI two wall portions for independently varying the" resonator frequency in opposite directionsjthe ends of each independently actuatable means being connected to said wall portions respectively.

11. High frequency apparatus comprisinga conductive hollow resonator body having exible generally parallel end walls formed with aligned electron-permeable regions, and means coupled to said walls for independently displacing each of said regions with respect to said body, yfor varying the width of the gap between said regions to selectively vary the resonator frequency.

12. Apparatus as in claim l1, wherein vsaid displacing means includes two thermally actuat" able longitudinally extensible means, one of said"V means for displacing one of said walls and the" other for independently displacing the other of said walls.

13. Apparatus as in claim 11, wherein said motion transmitting means includes manually actuatable means for displacing one of said walls and means for energizing one of said longitudinally extensible means for independently displacing the other of said Walls.

14. High frequency apparatus comprising a cavity resonator having a pair of flexible wall portions separately movable for independently varying the resonant frequency of said resonator, means including a thermally extensible member coupled to one of said flexible wall portions for flexing said wall portion upon electrical energi- Zation of said member to produce tuning of said resonator, manually adjustable means coupled to said one wall portion through said extensible member for manually adjusting said one wall portion and thereby. independently tuning said resonator, and a further thermally extensible member coupled to said resonator for exing the other of said flexible wall portions upon electrical energization of said further member, whereby further tuning of said resonator is effected.

15. High frequency apparatus comprising a cavity resonator having a pair of independently movable flexible wall portions each adapted to vary the resonant frequency of said resonator upon exing thereof. manually adjustable tuning control means coupled to said resonator for flexing one of said wall portions to produce tuning of said resonator, and bi-directional electrically excited thermally actuatable tuning means including a pair of electrically excited thermally extensible members coupled to the other of said Wall portions for producing movement thereof in one direction upon increase in excitation of one of said members and in opposite direction upon increase in excitation of the other member.

16. High frequency resonator apparatus comprising a cavity resonator having a pair of ilexible Wall portions independently movable for separately adjusting the resonant frequency of said resonator, manually actuated means coupled to one of said wall portions for producing controllable flexing thereof for tuning said resonator, a linearly extensible thermally actuatable electrically excitable member coupled to one of said Wall portions, means connected to said member for causing said member to produce move ment of said last-named one wall portion in a given direction upon increase in excitation of said member to vary tuning of said resonator in. one sense, a further linearly extensible thermally actuatable electrically excitable member coupled to one of said wall portions, and means coupled 1 to said latter member for causing said latter one wall portion to flex upon increase in excitation of said further member in a direction to produce variation in tuning of said resonator in the opposite sense, said manually actuated means being connected to one of said Wall portions through one of said linearly extensible thermally actuatable electrically excitable members, whereby tuning of said member may be independently effected either by said tWo members or by said manually controllable means.

17. High frequency resonator apparatus cornprising a cavity resonator having a xed body portion and a pair of independently exible wall portions, bi-directional thermally actuated tuning means having a pair of independently electrically excitable thermally extensible elements coupled to said resonator for producing variation in resonant frequency thereof in one sense upon increase of excitation of one of said members and for producing variation of said resonant frequency in opposite sense upon increase of excitation of the other member, and manually controllable means coupled to said resonator for producing tuning thereof independently of the excitation of said members.

18. Apparatus as dened in claim 17 wherein said pair of thermally extensible elements are connected to one of said flexible wall portions of said resonator, said manually controllable means being connected to the other of said Wall portions of said resonator.

LYNN R. HILDEBRAND.

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

UNITED STATES PATENTS Number Name Date 1,658,953 Theremin Feb. 14, 1928 1,884,591 Davis Oct. 25, 1932 2,079,809 Kul-lle May 11, 1937 2,146,365 Batchelor Feb. 7, 1939 2,183,215 Dow Dec. 12, 1939 2,251,085 Unk July 29, 1941 2,259,690 Hansen et al. Oct. 21, 1941 2,380,496 Beard July 31, 1945 2,408,817 Snow Oct. 8, 1946 2,414,496 Varian et al. Jan. 21, 1947 2,414,785 Harrison et al Jan. 21, 1947 2,434,294 Ginzton Jan. 13, 1948 2,468,145 Varian Apr. 26, 1949 FOREIGN PATENTS Number Country Date 537,518 Great Britain June 25, 1941

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