US2464230A - High-frequency apparatus - Google Patents

Description

March 15, 1949. A. E. HARRISON HIGH-FREQUENCY APPARATUS Filed May 20, 1944 m UE INVENTOR ARTHUR E. HARR [SON ATTORNEY was 2 m m S no Patented Mar. 15, 194.9

HIGH-FREQUENCY APPARATUS Arthur E. Harrison, Rockville Centre, N. Y., as-

signor to The Sperry Corporation, a corporation of Delaware Application May 20, 1944, Serial No. 536,467

The present invention relates to the art including ultra high frequency electron discharge tubes, and is more particularly concerned with such tubes wherein cavity resonators are used to vary the velocity of an electron beam, and the electrons are thereafter bunched.

In prior U. S. Patent No. 2,281,935, issued May 5, 1942, to R. H. Varian and W. W. Hansen, and in U. S. Patent application Serial No. 416,170, filed October 23, 1941, in the names of W. W. Hansen, J. R. Woodyard, S. F. Varian and R. H. Varian, and now Patent No. 2,4 5,738, issued August 19, 1947, there are disclosed vacuum tubes of the above type used as frequency multipliers, in which an electron beam, velocity bunched by the action of an input resonator tunedL to and excited at a first frequency, excites an output resonator tuned to a harmonic of the energizing frequency and spaced a predetermined distance from the input resonator.

It is an object of the present invention to provide an improved cavity resonator suitable for use in such frequency multiplier vacuum tubes, and having smooth and stable frequency characteristics.

It is a further object to provide an improved cavity resonator having an effective fixed lumped capacitance and an effective variable tuning capacitance.

Another object is to provide an improved electron discharge device having a cavity resonator embodying an inner cylinder rigidly positioned with respect to the outer shell of said resonator.

A further object is to provide an improved frequency multiplier or harmonic generator having an input resonator embodying an inner cylinder rigidly positioned with respect to the outer shell of said resonator.

Still a further object is to provide an improved velocity variation frequency multiplier or harmonic generator having an input resonator embodying an inner cylindrical conductor forming an electron drift tube rigidly positioned within an outer shell of said resonator.

Another object is to provide an improved input cavity resonator for a velocity variation frequency multiplier so constructed as to insure sub stantially coaxial relation between adjacent grids of said frequency multiplier input resonator.

Other objects will become apparent from the specification, taken in connection with the accompanying drawing, wherein the invention is embodied in concrete form.

In the drawing,

31 Claims. (Cl. 315-6) Fig. 1 is an elevation, partly in cross-section, of a velocity-variation electron discharge device adapted to be used as a frequency multiplier;

Fig. 2 is a view partly in cross-section, of an improved velocity-variation frequency multiplier embodying the principal features of the present invention;

Fig. 3 is an elevation, partly in cross-section, of a portion of a velocity-variation frequency multiplier similar to that shown in Fig. 2, showing an alternative arrangement for excitation of the velocity-variation device of Fig. 2; and

Fig. 4 is an elevation, partly in cross-section, of a somewhat different arrangement of elements in a velocity-variation frequency multiplier embodying the present invention.

Like reference numerals are used throughout the four figures to refer to the similar portions thereof.

In Fig. 1 there is shown a velocity variation frequency multiplier embodying an input cavity resonator 6 of a type disclosed and claimed in pending application 416,170 referred to above. This input cavity resonator 6 comprises as its principal elements the cylindrical outer shell 9, a rigid slightly conical end Wall 1, and an inner conductive cylinder 8 connected to outer shell 9 and movably supported therein by the flexible diaphragm ll forming an end wall of the resonator opposite the rigid end wall 7.

As will be explained in detail below, the velocity variation frequency multiplier embodying input resonator 6 includes a cathode structure it positioned adjacent end wall 1 of the input resonator, an output cavity resonator ll, means for adjusting the dimensions Within resonator 3 for tuning the input resonator to an excitation signal frequency, and means for tuning resonator ii to a harmonic of this frequency.

As discussed in more detail in the above-mentioned patent, the velocity variation frequency multiplier is operated with the cathode electrically heated for electron emission and supplied with high negative potential with respect to resonator 6. With a resonant source of ultra high frequency energy coupled to resonator 6 through a coaxial line l5, l5 and coupling loop M, a high-potential ultra high frequency electric field is developed between end wall I and the end 27 of inner cylinder 8 of resonator 6. Electrons are projected from cathode structure I3 through a central circular opening in end wall 7 to be propelled along through inner cylinder 8 into resonator ll, under the influence of tween end wall I and end 21? of inner cylinder 8,

the electrons are velocity modulated by the ultra high frequency voltage field produced in this region.

During the travel of the stream of electrons from this region along the drift space bounded .f

by inner cylinder 8, the velocity modulation results in distribution of the electrons in spaced bunches. These bunches pass through an ultra high frequency, high voltage field region of the output resonator ii, and impart thereto high harmonic energy. This ultra high frequency harmonic energy may be extracted from the out put resonator ll through coupling IE3 and applied to a suitable utilization device connected thereto.

A pair of closely adjacent grids 29 and may be provided in the end 2'! of the innercylinder i3 and in the opening in rigid end wall l, respectively. Such a pair of grids, along with the closely adjacent metal areas of rigid wall i and inner cylinder 8, serve as an effective lumped or concentrated capacitance which, together with the distributed inductance and capacitance of input resonator (5, determines the frequency of resonant response of the resonator.

In practice, it is often found that in order to allow resonator B to be built as a compact unit, it is necessary to employ a large lumped capacitance at grids 29 and 3!), which normally could be provided only by decreasing the spacing between the grids to less than a reasonable minimum value. In order to increase the lumped capacitance at this point, while retaining ample spacing between grids 23 and 30, a conductive slightly conical flange 28 was attached to the end 27 of the inner cylinder 8, as described in the pending application referred to above. The member 28 cooperates with rigid end wall 7 to provide addi tional capacitance, which acts in shunt with the capacitance between grids 29 and '30 to tune resonator 6 to a desired input frequency range.

The structure provided for tuning input resonator 6 comprises a flange 23 rigidly attached to outer shell 9, and a second flange 2d rigidly connected to an extension it! of inner cylinder 8. A plurality of screws 21, ill may be provided in suitably tapped holes through flange 23 for bearing against flange 24 to adjust the separation between the flanges. Although only two such screws are shown in the view of Fig. 1, there may be three input resonator tuning screws employed in suitable threaded holes symmetrically located at 120 intervals through flange 23.

If the input tuning screws are provided with righthand threads, clockwise rotation of the screws is used to produce movement of inner cylinder 8 axially away from rigid end wall l, to decrease the capacitance therebetween and thus to tune resonator 6 to resonance at a higher frequency.

A similar structure for tuning harmonic output resonator l1 comprises a rigid metal plate 25 connected to the metal cylinder 53 extending within resonator ii to form a movably supported part thereof. This plate, also may be provided with three tapped holes spaced at 120 intervals and accommodating output tuning screws 22 which have rounded ends adapted to bear against the rigid flange 24.

Three springs 26 interspaced among output with the new frequency Was achieved.

resonator tuning screws 22 and also among the input tuning screws may be stretched between flange 23 and end plate 25, through clearance holes provided in flange 24. These springs provide axial tension for maintaining input tuning screws 2!, 2i and output screws 22 firmly seated against the flange 24 which is common to the input and output tuning structures.

In practical operation of the device shown in Fig. 1, a cathode heating supply and a high potential source are connected as described above, to provide cathode electron emission and accelerating potential along the electron path. A utilization device, such as a detector, is connected to output coaxial line it, and a source of ultra high frequency excitation energy is coupled to the input resonator 6 through a coaxial line I5, US. may be of the order of 300 megacycles per second, for example.

The input resonator 6 is then tuned. by means of adjustment screws 2i, 2! to the frequency of the excitation source coupled thereto, and the output resonator ll is tuned to the desired harmonic of the input frequency, e. g., the tenth harmonic, which in the above example would be of the order of 3000 megacycles per second.

The device shown in Fig. 1 was found to be diiiicult to adjust forbest performance; this was noted to be especially due to critical movements of the input tuning screws, 2|, 2! required. for obtaining maximum harmonic output energy from resonator l'i. When a large change of resonant frequency of the resonator 6 wasrequired to reach resonance with acoupled source of excitation signal, it was necessary to make small successive adjustments on all of the input resonator tuning screws in turn, repeating this procedure in a number of steps untilresonance Even then, the resonator. 6 often was found to perform unsatisfactorily unless minute adjustments of the different input tuning screws were made to find the most effective combination of positions of all of the input resonator adjusting screws.

After several successivev adjustments of .the input resonator tuning screws, retracting one and advancing another, an adjustment of resonator 6 eventually could be found at which very good performance was obtained.

The critical adjustment characteristics of input resonator 6 were believed to be largely due to the great axial extension of inner cylinder 8 from an effective pivotal point in the vicinity. of flexible diaphragm l l. Because of this, an advancement of a single input resonator tuning screw, e. g., 2 l, while eifective as intended to produce axial movement of inner cylinder 8 with respect to outer shell 9, also resulted in a radial movement of the end 27 of inner cylinder 3 which. was much greater than the resultant axial movement, Of course, only the axial movement was desired, since it was advantageous to retain grids 29 and 30 in substantially coaxial positional agreement, so that the respective parts of the grids would remain aligned.

Moreover, the lumped loading capacitance provided by closely spaced elements 1 and 28 varied sharply when a relative radial movement between these elements was produced by such differential adjustments of screws 2| and 2i.

Of course, in the design of the frequency multiplier electron discharge device of Fig. 1, it was intended that large axial movements of element 28 and grid 29 with respect toendwall' 1 The frequency of the excitation source movements to negligibility.

and grid 30 for tuning over a large frequency range would be accomplished with negligible radial motion of elements 28 and 29 with respect to elements 1 and 30, by successive small adjustments of each of the input resonator tuning screws in turn. Actually, however, it was found difficult to so regulate the rotary adjustments of the tuning screws as to restrict the above radial Furthermore, the alignment of the elements 8 and 28, and of elements 29 and 30 within the resonator 6 could only be estimated on the basis of the performance of the frequency multiplier tube, since these elements were hidden from view.

Then, too, while large changes of tuning of the input resonator were accomplished by small, successive movements of the difierent input resonator screws in turn, the relatively small final tuning adjustments of the input resonator usually required concentration on a single adjustment screw, as screw 2|, adjustment of which would result in greater radial movement of elements 28 and 29 than axial movement of those elements, as explained above.

Thus, the structure shown in Fig. 1 of the drawing in this case, and shown and claimed in the above-mentioned application Serial No. 416,170, operated successfully after a tedious series of adjustments, but required great care in manipulation of the individual input resonator tuning screws to obtain best performance.

The present invention, in order to overcome the disadvantages above recited, provides in the frequency multiplier or harmonic generator of Fig. 2 an improved input cavity resonator characterized by substantially fixed alignment of the input resonator grids and the cathode, and further characterized by an inner cylinder 3 rigidly positioned within shell 9. A further feature of this improved cavity resonator is the incorporation therein of a rigidly fixed capacitance loading element 33 extending between the end 27 of the inner cylinder 8 and the corresponding end of outer shell 9. This fixed capacitor is supplemented by an adjustable lumped capacitor comprising a metal cylinder 31 and element 36 movable axially in closely spaced relation to the end 21 of inner cylinder 8. Metal cylinder 31 and element 35 are separated axially from the end of inner cylinder 8 by a small annular gap which is varied by movement of element 36.

With these features the resonator 8' overcomes the critical adjustment characteristics of the operation of the resonator 6 shown in Fig. 1.

In the form of resonator shown in Fig. 2, the rigid electrically conductive cylinder 8 is rigidly connected to outer shell 9 through rigid conductive end plate 32. Cylinder 3 and end plate 32, together, form a rigid conductive re-entrant member connected to outer shell 9 at one end thereof. Such a re-entrant member may be composed of a disc portion and a cylindrical portion bonded together, or may be made as a unit by spinning or drawing a single piece of metal to the desired form. A large lumped loading capacitance is provided between the ends of outer shell 9 and inner cylinder 8 by a conductive member 33 attached to cylinder 8 and extending between cylinder 8 and outer shell 9. Preferably, element 33 may include a disc portion 33' and a cylindrical portion 33", the latter having an outer diameter slightly smaller than the inner diameter of shell 9. Such portions, if desired, may be formed as a single metallic member spun from suitable sheet metal. The cylindrical portion of element 33 provides a large capacitance concentrated between this element and the inner surface of the cylindrical shell 9.

Attached to the end of shell 9 adjacent capacitance element 33 is an end wall 34 provided with a flexible diaphragm 35 which permits movement of adjustable flanged tuning element 38 relative to the end 2? of inner cylinder 8 and also relative to the disc surface 33 of fixed capacitance loading element 33. Flange 33 is connected through cylinder 31 to rigid flange 38, which in turn is attached through metal cylinder 39 and a glass extension 4| to a conventional vacuum tube base d2. Within the metal cylinder 39 is positioned a cathode structure I 3 similar to that shown in Fig. 1. Also there is positioned within flange 38 an accelerating grid 4'4 adapted to cooperate with cathode structure l3 in projecting electrons axially along resonator 6' through the drift tube space within conductive cylinder 8.

Adjustment screws 45 cooperating with suitably tapped holes through flange 38, and compressed springs 56, provide means for adjustment of the spacing or gap between adjustable capacitor element 35 and the end 21 of inner cylindrical conductor 8. Thus, while the large lumped capacitance provided by the closely spaced element 33 and shell 9 of the cavity resonator remains substantially constant by virtue of the rigid construction of these parts of th cavity resonator, tuning element 36 may be variably positioned within the cavity resonator to provide resonant frequency adjustment throughout a predetermined small frequency range.

Th flanged tuning element 36 may be arranged to cooperate with the disc surface 33 of fixed loading capacitor element 33 as well as the end 27 of inner cylinder 3, if a moderately wide range of input resonator tuning adjustment is desired. The flanged tuning element 33 not only provides for a desired range of tuning adjustment, but also serves a very important additional purpose in the structure shown in Fig. 2, by electrostatically shielding the disc surface 33' of fixed capacitor loading element 33 from flexible diaphragm 35. Even though the position of the cylindrical member 31 is fixed with respect to shell 9 of the cavity resonator for a given adjustment of tuning screws 45 so that the outer and inner circular edges of diaphragm 35 are fixedly positioned, variations of atmospheric pressure due to barometric changes or to impinging sound waves may cause movements or vibrations of the portion of flexible diaphragm 35 intermediate the inner and outer circular extremities thereof. Without the tuning flange 36 interposed between flexible diaphragm 35 and the disc face of the capacitance loading element 33, an appreciable variation of capacitance, and accordingly, an appreciable variation of resonator tuning would be caused by such movements of the flexible diaphragm.

By virtue of the unusual arrangement of parts in resonator 6', the flanged tuning element 36 is at substantially the same ultra high frequency potential as diaphragm 35, so that small changes of capacitance between adjacent surfaces of these elements are of negligible effect on the resonant frequency of the resonator 6.

An output resonator ll comprising a cylindrical outer wall 5|, a flexible diaphragm 52 and an inner conductive cylinder 53 may be fastened to rigid end wall 32, employing the outer surface 54 of this wall of the input resonator as a conductive surface portion of cavity resonator I1.

Coaxial line l8-is sh'owrl'prcvided with a coupling loop 55 extending within cavity resonator l? for extraction of ultra high frequency energy therefrom.

Tension springs 25 and adjustment screws 22 are provided in a disc or flange 25 rigidly connected to inner cylinder 53 of the output resonator. These adjustment screws and springs permit the spacing between disc wall surface d and the inner cylinder 53 of the resonator H to be adjusted as desired for tuning the resonator H to a desired harmonic of the input resonator excitation signal. Grids fat and il may be provided Within wall surface 55; and inner cylinder 53, respectively, if desired.

In the construction of an input resonator 6 as shown in Fig. 2, care must be exercised to insure that the large capacity loading element 33 is so dimensioned, relative to the dimensions of the inner cylinder 3 and the outer cylindrical shell 9, as to tune the resonator 5 to a frequency slightly higher than the desired operating frequency. The small variable capacitance added by the flanged capacitance element then provides adjustment of the tuning of resonator B to the precise frequency desired.

In Fig. 2, a coupling loop ill and a coaxial line having an inner conductor l5 and an output conductor i6 is shown inserted at a point of low potential and high current and magnetic field strength within the resonator 5. Such a coupling element is suitable for introduction of low frequency power into the resonator ii from a low impedance source. If desired, however, a high 1'. .pedance input coupler may be provided in resonator 6' as shown in the partial view in Fig. 3, wherein is shown a modification of the structure of 2 to provide a conductive lead 52 fixedly positioned in an opening through outer shell 9 by a glass seal 53 and connected to a capacitance loading element 33 as by a soldered joint 6- 5. An outer tubular conductor 65 connected to outer shell 9 as by a soldered joint may be provided along with lead to form therewith a high impe ance coaxial line for input connection to the resonator b. If an intermediate impedance coupier is desired the conductor 62 may be connected to any point along inner cylinder it instead of capacitance loading element Figure l shows a modification of the structure of Fig. 2, in which the rigid relation of the cylindrical conductor 8 and the outer shell ii is retamed a the inner cylinder 8 encloses the oathode assembly it on an insulated supporting structure 68. With this arrangement, the direction of the electron stream projected from the oathode structure 53 through the grids 29 and 3d of resonator S is substantially the opposite of that shown in Fig. 2, so that the electron drift tube til may be made external of the resonator 6 and may be made of any length shorter than resonator 5" if desired. This has the advantage of permitting greater design flexibility of resonator ii, substantially independent of the drift tube length requirements of a velocity variation frequency multiplier tube structure.

In Fig. 4, conductive cylinder 29 supporting at one end the flanged tuning member 36' is rigidly fastened to adjustable flange "l, and is extended beyond this flange to provide the inner cylindrical conductor l2 of output resonator Ii. A rigid fiange 58 is provided on output resonator l? for adjustment through screws 51 of the spacing between output resonator grids 59 and 6! for changing the lumped capacitance therebetween *to' tune the resonator. For this purpose, screws against flange ll.

*lange l l is also adjusted with respectto'end wall t l of input cavity resonator 6"by screws which are seated in threaded holes through flange H and bear against wall 34' to permit relative adjustment of the spacing betweenfiaiiged tuning element 36' and the disc portion of'the lumped capacitance loading element 33.

Otherwise than in the revision of the input resonator to permit the location of the cathode structure it within the boundaries of the resonator ii, and thus to permit a choice of drift tube length substantially independent of the length of resonator ii", the operation of the version of Fi 4 is substantially similar to that of the arrangement shown in Fig. 2, as will now'be described.

With the negative terminal of a source of high potential connected to cathode structure it '(or iii) and the positive terminal connected to the metallic resonator structure E (or t") and with a source of filament heater potential connected heat the cathode element within cathode structure ill (or E3), source of ultra high frequency energy be connected to the input coaxial line it, it or to the high impedance coaxial line '32, E5, and input resonator t (or 6") easily may be tuned by adjustment of tuning screws 45 (or iii) to resonance with said ultra high frequency source. With an ultra high frequency utilization device, such as a detector, connected to output coaxial line it, tuning screws 22 (or 5i) may adjusted to tune output resonator ll (or ll) for maximum output at a desired harmonic of the energy supplied to the input resonator.

The improved non-critical performance of the input resonator embodying the present invention may then be observed by rotation of one of the input resonator tuning screws 55 through a small angle in a clockwise direction, and a similar rotation of another input tuning screw threaded in a similar sense through an equal angle in the opposite direction. With the first of these adjustments, it will be noted that the resonator 5 is detuned from resonance with the source connected to coaxial line I5, H5, resulting in a marked decrease of output from coaxial line it. With the second of these adjustments, the axial alignment of cathode structure it andcylindrical structure 3? is shifted only very slightly with respect to the axis of shell 8 and inner cylinder 8, and the tuning of resonator B is readily restored to resonance with the source connected to coaxial line l5, It without any detectable relative radial displ-..c merit between grids 29 and fill, and thus without appreciable impairment of performance of the electron discharge device.

Thus, by the rigid positioning through end wall 32 of inner conductive cylinder 3 and capacitor loading element with respect to outer shell 9, and the very short axial length of the structure connecting flange 3a (or ill) and the adjustable flange (or $33) the radial movement of flange element at resulting from rotation of a tuning screwiii to obtain desired axial movement of this element with respect to the end 21 of inner cylindrical conductor i2 is greatly reduced. This results in high, mechanical and electrical stability of input resonator and permits greatly improved ease of timing adjustment of the input resonator. u I

Along with this improved. arrangement of elements in resonator 6', the radial extension of the flanged tuning element 35 is made sufficient to efiectively shield the flexible diaphragm 35 from the relatively high potential surface of fixed capacitor element 33 and the end 21 of inner cylinder 8, thus safeguarding against vibration and pressure-responsive modulations of the energy supplied to input resonator 6.

Since many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

l. Cavity resonator apparatus comprising a conductive outer shell havin a flexible wall at one end, a rigid conductive inner member fixed to said shell at the other end thereof and extending toward and adjacent to said flexible wall, conductive means supported at the central portion of said flexible wall and opposite the end of said inner member and defining a gap therebetween, for controlling the resonant frequency of said resonator, and shielding means adjacent said flexible wall for preventing vibration of said wall from modulating said resonant frequency, said shielding means comprising a disc positioned adjacent said gap.

2. Cavity resonator apparatus comprising a conductive outer shell having a flexible wall at one end, a rigid conductive inner member extending from the other end of said outer shell toward said flexible wall, conductive means supported at said flexib e wall and opposite the end of said inner member and defining a gap between said inner member and said conductive means, and shielding means adiaccnt said flexible wall and extending radially a distance smaller than the inner diameter of said shell and intermediate said flexible wall and said end of said inner member for preventing distortion of said wall from affecting the resonant frequency of said resonator.

3. Apparatus as in cTaim 2 further including means connected between said conductive means and said shell for varying said gap whereby the resonant frequency of said resonator may be varied.

4. Cavity resonator apparatus comprising a conductive outer shell having a flexible wall at one end, a rigid conductive inner member fixed to said shell at the other end thereof and extending toward and adjacent to said flexible wall, conductive means supported at the central portion of said flexible wall and opposite the end of said inner member and defining a gap therebetween, means connected between said latter conductive means and said shell for varying said gap to vary the resonant frequency of said resonator, and shielding means adjacent said flexible wall for preventing distortion of said wall from affecting said resonant frequency, said shielding means comprising a conductive disc member located adjacent said gap and connected to said flexible wall and between said flexible wall and said inner member.

5. An ultra-high frequency cavity resonator comprising a conductive cylindrical outer shell having a rigid conductive wall attached at one end and a flexible conductive diaphragm attached at the opposite end, a conductive inner cylinder positioned within said outer shell and rigidly connected at one end to said rigid Wall and extending toward said flexible diaphragm and providing lumped capacitance therewith, a fixed capacity-loading element extending between said inner cylinder and said outer shell and fixedly positioned with respect to said cylinder and said outer shell and means for varying said lump capacitance, comprising means connected to said flexible diaphragm for axial adjustment thereof toward said inner cylinder.

6. An ultra high frequency cavity resonator comprising a conductive outer shell having a rigid conductive wall attached at one end and a flexible conductive diaphragm attached at the opposite end, a conductive inner cylinder positioned within said outer shell and rigidly connected to said rigid end wall and extending toward said flexible diaphragm, a fixed capacitance loading element extending between said inner cylinder and said outer shell and fixedly positioned with respect to said cylinder and said shell and providing a large capacitance therebetween and a movable shielding flange connected to said diaphragm and extending radially between said diaphragm and said conductive inner cylinder whereby the direct capacitance between said flexible diaphragm and said inner cylinder is rendered substantially ineffective.

7. Apparatus as in claim 6, wherein said fixed capacitance loading element comprises a conductive cylinder positioned adjacent the inner surface of said outer shell at said opposite end thereof and connected to the end of said inner cylinder adjacent said diaphragm.

8. Ultra-high frequency electron discharge apparatus comprising a conductive cylindrical shell, a flexible conductive diaphragm connected to said shell at one end and having an opening through the central portion thereof, a rigid conductive disc connected to said shell at the other end, a conductive tube coaxially positioned within said shell and fixedly connected to said disc and also extending therefrom substantially the length of said outer shell toward said flexible diaphragm, a fixed capacitance loading element fixedly positioned coaxially with said shell and said tube adjacent said flexible diaphragm through at least part of the radial spacing between said shell and tube, means including a cathode for projecting electrons through said conductive tube substantially parallel with the axis of said shell, and means coupled between said diaphragm and said conductive tube for varying the axial spacing between said flexible diaphragm and said conductive tube for varying the tuning of said apparatus.

9. Ultra-high frequency electron discharge apparatus comprising a conductive cylindrical shell, a flexible conductive diaphragm connected to said shell at one end and having an opening through the central portion thereof, a rigid conductive end wall connected to said shell at the other end, a first conductive tube coaxially positioned within said shell and fixedly connected to said end wall and also extending therefrom substantially the length of said shell toward said flexible diaphragm, a second conductive tube coaxially positioned within said shell and connected to said diaphragm and extending therefrom toward said first conductive tube, a first conductive disc located adjacent one end of said first conductive tube and extending radially to almost contact said shell, said first disc having an axially extending flange positioned at the periphery thereof parallel to and spaced from said shell, 2. second conductive disc located adjacent one end of said second conductive tube, said first and seca r-cease conductive discs forming a variable lumped c acitance, saidfiange portion of said first disc and: the adjacent portion. ofsaid shell formin a fixed lumped capacitance, means including a cathode for projecting electrons through said conductive tubes Substantially parallel with the axis of said shell, and means for varying the axial spacing between said first and second conductive tubes for varying the tuning of said apparatus.

10. Ultra high frequency apparatus comprising a resonator comprising a conductive outer shell having a rigid end wall and an opposite-end wall, a conductive cylinder fixedly positioned within said shell by a connection to said rigid end wall-and extending axially within said shell to ward'sald opposite wall-to substantially the axial extent of said shell, a fixed capacitance loading element extending substantially between said shell-and the end of saidiinner cylinder adjacent:

said opposite end wall, and an axial tuning ele ment supported in said opposite end wall and movable for adjustment relative to the adjacent end of said inner cylinder whereby the tuning of said resonator may be varied through a narrow frequency range.

11. Apparatus as in claim 10, wherein said tun ing element includes a radially extending conductivefiange between said opposite wall and saidinner: cylinder for electrostatically shielding said opposite wall from said innercylinder.

12. Ultra highirequency electron discharge apparatus comprising a conductive outer shell having a rigid endwall and an opposite end wall', a

conductive cylinder fixedly positioned with respect tosaid shell by aconnection to said end wall= within said tuning eiement, a second grid posi tioned' in the end of saidinner cylinder adjacent said tuning element, and means. including a source of electrons positioned coaxially with said inner cylinder and for projecting said electrons through said grids and said inner cylinder for oscillatory coupling therewith.

13.- In a velocity variation harmonic generator comprising an ultra high frequency input resonator, an output resonator or positioned coaxially with said input resonator and adapted to be tuned to harmonic relation with said input resonator means including, a cathode positioned adjacent said inputresonator for projecting electrons along an axial path through said input resonator and said output resonator in turn, the input resona tor comprising a conductive outer shell having a rigidendwall, a conductive cylinderfixedlypositioned within said shell'by a connection to said end'wall andextending axially within saidshell to substantially the axial extent of said shell, a

fixed capacitance loading element extending be of said inner cylinder wherebythetuning of said 12 l; resonator may be varied through a narrow frequency range.

14:. A velocity variation harmonic generator as in claim 13 wherein said cathode is positioned adjacent tuning element for projecting electrons through said tuning element and said inner cylinder in turn whereby said inner cylinder provides an electron drift space.

15. A velocity variation harmonic generator as in claim 14 wherein cathode is positioned within said inner cylinder for projecting elec rons therefrom through said tuning element.

16. An ultra iiin frequency'cavity resonator corn; i conductive wail attached at one end and a flexible conductive diaphragm attachedat the opposite end, conductive inner cylinder positioned within said outer bell and rigidly connected one end to said. rigid "wall and extending substantially of said shell toward said fiexible diaphragm to form an inner conductive surface of said resonator, and" means attached to said flexible diaphragm and extending toward said inner cylinder a stream of eiectrons therethrough; said cavity resonator comprising a conductive outer shell having a flexible wall at one end, a rigid holiow conductive 'innermember fixed to said shell at supported at thecentral portionof flexible wall and opposite the end of said inner member and defining a resonant-frequency-controlling gap therebetween for traversal by said electron stream,- and shielding means adjacent said flexiole wall for preventing distortion of said wall from affecting said resonant frequency.

18. Cavity resonator apparatus comprising a conductive outer shell having a flexible wall at one end, a rigid conductive inner member fixed to said shell at the other end thereof and extending toward an'd'adjacent to said flexible wall, conductive means supported at the central portion of said fiexible wall and opposite the end of said inner member and defining a gap therebetween, for controlling the resonant irequencyof said resonator and shielding means adjacent said flexible wall for preventing distortion. oi said wall from affecting said resonant frequency, shielding comprising a flanged member connected'to said flexible wall and between said flexible wall and said inner member.

19. An ultra high frequency cavity resonator comprising'a conductive outer shell having a wall at one end, a conductive inner member rigidly connected to said shell at the other end thereof and extending toward said wall, a capacity-deading element extending between said inner member near an end'thereof and said shell and rigidly fixed with respect to said member and said shell, and a movable member connected to the central portion of said end wall and defining a variable gap with the inner end of said inner member.

20. Anultra high frequency cavity resonator sing a conductive outer shell having a rigid ig effectively lumped. capacitance therewith, said capacitance means 1e other end thereof and extending toward and adjacent to said flexible wall, conductive means said comprising a conductive outer shell having a first conductive Wall attached at one end and a second conductive wall attached at the other end, an inner conductor coupled to said first wall and ex-- tending toward said second Wall and providing a lumped capacitance therewith, and a capacity loading member connected to said inner conductor and forming lumped capacitance with said second wall and said outer shell.

21. Apparatus as in claim 20 in which one of said lumped capacitances is variable.

22. Apparatus as in claim 26 in which one of said lumped capacitances is fixed.

23. Electron discharge apparatus comprising an ultra high frequency cavity resonator means a cathode positioned adjacent to said i for projecting a stream of electrons therethrough, and means for coupling a source of high frequency oscillations to said cavity resonator for velocity modulating said stream of electrons; said cavity resonator comprising a conductive outer shell having a wall at one end, a hollow conductive inner member rigidly connected to said shell at the other end thereof and extending toward said end wall, a capacity-loading ele ment extending between said inner member near the end thereof and said shell and rigidly fixed with respect to said inner member and shell, and a movable member connected at the central portion of said end Wall and defining a variable gap with the inner end of said inner member.

24. A high frequency cavity resonator comprising a rigid outer shell, an inner member connected to said rigid outer shell and extending axially therewithin, means extending between said inner member said outer shell for providing fixed efiective lumped capacitance therebetween, and further means extending between said inner member and said outer shell for providing variable eiiective lumped capacitance therebetween.

25. A resonator comprising a conductive outer hell, an inner conductor coaxial with said outer shell and connected therewith, conductive means connected to said inner conductor for providing a fixed lumped capacitance between said outer shell and said inner conductor, and further means extending between said outer shell and said inner conductor for providing variable lumped capacitance therebetween.

26. An electron discharge device comprising a cathode an output resonator, and an input resonator ing a pair of electron-permeable wall portions positioned intermediate said output resonator and cathode, and comprising a pair of rigidly connected coaxial members having rigidly fixed lumped capacitance and variable lumped capacitance therebetween.

27. A resonator device comprising a pair of rigidly connected coaxial members having distributed capacitance, fixed lumped capacitance and variable lumped capacitance therebetween.

28. An ultra-high frequency cavity resonator comprising a conductive outer shell having a first conductive wall attached at one end and a second conductive wall connected to the other end, an inner conductor coupled to said first wall and extending toward said second wall, and a capacity loading means connected to the inner conductor and extending radially to almost contact the outer shell, 2. part of said capacity loading means forming lumped capacitance with the said outer shell, and a iurther part of said capacity loading means forming a variable lumped capacitance with said second wall.

29. Apparatus as in claim 28 in which means are provided for varying with a minimum of radial displacement the axial spacing between the end of inner conductor extending toward said second wall and said capacity loading means.

39. An ultra-high frequency cavity resonator comprising a conductive outer shell having a rigid conductive wall attached at one end and a flexible conductive diaphragm attached at the opposite end, ccndt ive inner cylinder positioned within said outer shell and rigidly connected at one end to said rigid wall and extending substantially the length of said shell toward said flexible diaphragm to form an inner conductive surface of said resonator, a movable conductive disc spaced from said flexible diaphragm and adjacent the end of said inner cylinder adjacent said diaphragm, and a capacity loading means connected to said one end of said inner conductor and extending almost to the inner surface of said outer shell, 9. part of said capacity loading means forming fixed lumped capacitance with said outer shell, and a part of said loading means formin variable lumped capacitance with said disc.

31. Apparatus as in claim 39 wherein positioning means having a substantial pivotal point are provided for regulating with a minimum of radial movement the axial spatial separation of said disc and said capacity loading means, the axial distance from the end of said disc to said pivotal point being small, whereby said radial movement is minimized.

ARTHUR E HARRISON.

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

UNITED STATES PATENTS 2,408,355 Turner Sept. 24, 1946

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