US2487800A - Frequency multiplier and stabilization cavity resonator apparatus - Google Patents

Description

1949 -w. w. HANSEN FREQUENCY MULTIPLIER AND STABILIZATION CAVITY RESONATOR APPARATUS 2 Sheets-Sheet 1 Filed Jan. 22, 1943 INVENTQR WLLiAM W. HANSEN BY w/fiyfl r ATTQRNEY Nov. 15, 1949 Filed Jan. 22, 1945 w. w. HANSEN 2,

FREQUENCY MULTIPLIER AND STABILIZATION CAVITY RESONATOR APPARATUS 2 Sheets-Sheet 2 III ENVENTOR WILLIAM W. HANSEN W mA I ATTORNEY I 0301mm? Patented Nov. 15, 1949 UNITED FREQUENCY MULTIPLIER AND STABILIZA- TION CAVITY RESONATOR APPARATUS William W. Hansen, Garden City, N. Y., assignor to The Sperry Corporation, a corporation of Delaware Application January 22, 1943, Serial No. 473,254

9 Claims.

The present invention is related to the art including frequency multipliers, especially for ultra high frequencies of the order of cycles per second or higher.

The present device utilizes the principle of velocity variation or velocity modulation set forth in Varian Patent No. 2,242,275, issued May 20, 1941, but, as will be shown below, may be utilized with many other types of electron discharge devices. In this patent, an ultra high frequency oscillation generator is described in which an electron beam is acted upon by the high frequency field in a first or buncher hollow cavity resonator to produce periodic velocity variations of the electrons. These velocity-varied electrons are then projected through a field-free space in which the higher velocity electrons overtake the lower velocity electrons, producing recurrent bunching along the beam. This bunched beam is t n P jected through a second or catcher hollow cavity resonator, which abstracts energy from the I beam at the operating ultra high frequency. A portion of this energy may be regeneratively fed back to sustain and maintain the velocity variations of the beam, if the device is to act as an oscillator and the remainder of the energy in the resonator is then available for use as desired. The electrons, after giving their energy to the catcher resonator, are suitably collected and returned to the cathode.

In devices of this type, the velocity varying or buncher" resonator operates at and has the same resonant frequency as the energy pick-up or catcher resonator. It is often desirable to synchronize such an oscillator with a different source of high frequency energy. For example, sources of high frequency energy of several types producing frequencies of the order of several hundred megacycles per second are readily available, and it is often desirable to synchronize or lock-in an ultra high frequency oscillator of the above velocity-variation type with such a relatively low frequency oscillator; that is, to maintain a harmonic relation between these oscillators. By thus supplying relatively low frequency energy or medium frequency energy to the ultra high frequency oscillator and exciting or driving the oscillator in this way, larger amounts of ultra high frequency power, and improved frequency stabilization may be produced. The present invention provides apparatus for accomplishing this desirable purpose.

In the following, the term relatively low frequency is intended to designate a frequency of 300 megacycles per second or less, corresponding to wavelengths greater than one meter.

Accordingly, it is an object of the present invention to excite or drive an ultra high frequency velocity variation oscillator by means of a relatively low frequency wave.

It is a further object of the present invention to stabilize the frequency of an ultra high frequency velocity variation oscillator from a relatively low frequency source of oscillations.

It is'another object of the present invention to provide improved apparatus for producing ultra high frequency oscillations of a frequency harmonically related to that of a relatively low frequency source of oscillations.

Further objects and advantages will become apparent from the attached specification and drawings, wherein Fig. 1 shows a schematic diagram of one form of driven high frequency oscillator according to the present invention.

Fig. 2 shows a schematic diagram of a modification of the apparatus of Fig. 1, and

Figs. 3-5 show schematic diagrams of further modifications of the device of Fig. 1, and

Figs. 6 and 7 show fragmentary views of modi fications of portions of Figs. 1-5.

Referring to Fig. 1, reference numeral ll refers to an ultra high frequency velocity variation oscillation generator of the type shown in the above-mentioned Varian Patent No. 2,242,275. This generator comprises a thermionic cathode I2 heated by filament H] and acting as a source of electrons, which are projected under the influence of a battery 33 in the form of an electron beam through grids l3 and I4 forming a portion of the walls of a hollow resonant cavity or resonator l6 having a'resonant frequency substantially the same as or close to the desired output frequency of the apparatus. Any high frequency alternating electromagnetic field existing within resonator l6 will produce recurrent velocity variations of the electrons passing between grids l3 and M. The electrons then exiting from grid l4 pass through a field-free drift tube l1 whose length is so selected that, by the time these electrons arrive at the further grid [8, they are grouped to form recurrent bunches along the electron stream. Grids l8 and 19 form portions of the walls of a further energy pick-up or catcher resonator 2| and deliver high frequency energy at the operating frequency to the field within resonator 2|. A portion of this energy is fed back to launcher resonator I6, as by way of a suitable coupling loop 23, connecting concentric transmission line 24, and coupling loop 26. A further coupling loop 21 and concentric transmission line 28 are provided, from which useful high frequency energy may be derived from resonator 2|, for use wherever desired. The electrons passing through grid l9 are collected by a suitable collector electrode 29, which may form a part of the evacuated conductive housing of the device or may be a separate insulated electrode. Preferably, the evacuated housing is substantially completely metallic and grounded, as at 3|, the cathode l2 being insulated therefrom by means of a suitable insulating seal 32 and operated at a high negative potential by means of battery 33 connected thereto through a radio frequency choke coil 33.

The circuit thus far described is essentially identical with that disclosed in the above-mentioned patent No. 2,242,275 and will operate as a self-sustained ultra high frequency oscillation generatorto produce oscillations of the frequency 'w to which resonators l6 and 2|are tuned. However, to stabilize the frequency output of this oscillator, and to increase the power output therefrom, it is desirable to excite or drive this oscillator from a further source of oscillations, which, according to the present invention, may be of a much lower frequency, for example, the frequency of the desired output frequency. Such a stabilizing frequency maybe derived from a suitable oscillator 34 of any conventional type. As an illustrativeexample, the output of oscillator 34 may have a frequency of the order of .300 megacycles per second, and the resonators l6 and 2| may be tuned to a frequency of the order of 3000 megacycles per second centimeters wavelength) whereby a 10 to 1 frequency multiplication may be obtained.

The output of oscillator 34 is coupled, as by means of a suitable radio frequency transformer 36, to a tuned circuit 31 connected between cathode l2 and grounded grid l3 through a high capacity blocking condenser 36. Accordingly, an alternating voltage of the frequency of oscillator 34 is thus impressed between cathode l2 and grid l3. Choke 30 prevents this voltage from being shortcircuited to ground through battery 33. Any other ways of impressing this Voltage between cathode l2 and grid l3, such as shown in Figs. 3 and 4, may be used here, as described. This voltage produces a modulation of the electron stream flowing from cathode [2 at a frequency corresponding to that of oscillator 34. It has been discovered that such a modulation of the electron stream permits oscillator H to operate satisfactorily only at a frequency which is an exact harmonic of oscillator 34, when the resonant frequency of oscillator II is close to a harmonic of that of oscillator 34, by virtue of the phase relations existing between the relatively low frequency modulation of the electron stream caused by oscillator 34 and the high frequency variations produced by the field within resonator By the present arrangement, therefore, the frequency output of the oscillator II, as derived by way of line 28, is accurately stabilized by that of oscillator 34. As is well known, oscillators of relatively low frequency, such as oscillator 34, are much more easily stabilized by Well-known means such as quartz crystal devices, than the ultra high frequency oscillators of the type of oscillator II. By the present circuit, therefore, the stability characteristics of oscillator 34 are transferred to oscillator H, and a greatly improved frequency stabilization of the output of oscillator I I is produced. Furthermore, by initiall modulating the electron stream from cathode [2 before it enters the space between grids l3 and I 4, the time required to build up oscillations in the oscillator II to a useful value is greatly reduced, and its power output is also increased.

Fig. 2 shows the application of the same principle to a slightly different type of velocity variation oscillator 4|, known as the reflex type which is described more in detail in Varian et al. Patent No. 2,250,511, issued July 29, 1941, and

vand a further resonator 2| l0 especially with respect to Fig. 2 thereof. In this type of oscillator, the electron beam from cathode I2 is projectedthrough the grids l3 and 14 of a single resonator 42 containing an alternating Thigh frequency electromagnetic field, whereby velocity variations of the electrons of the beam are produced as in Fig. 1.

However, instead of providing a drift tube I! as in Fig. 1, the electron stream is caused to reverse its direction by .means of a' suitable reflecting electrode 43 having a potential substantially the same as or only slightly more positive than the potential of cathode l2. By properly spacing electrode 43 from grid l4, the electron beam is bunched as it re-enters resonator 42, and sustained oscillations are maintained within the resonator 42 whereb ultra high frequency energy may be supplied to an external utilization device by means of a suitable connecting line 44.

The oscillator H of Fig. 2 may be synchronized with and multiplies the frequency of the relatively low frequency oscillator 34 in much the same -manneras in Fig. 1, by choosing the resonant frequency of resonator 42 close to a harmonic of the frequency of oscillator 34. Thus, the voltage output of oscillator 34- is impressed between cathode l2 and grounded grid I3 'of oscillator 4! by way of transformer 36, tuned circuit 31 and coupling and blocking condenser 38, as in Fig. 1. The device of Fig. 2 will therefore operate in the same manner as that of Fig. 1, to produce an ultra high frequency output which is harmonically related to the relatively low frequency of oscillator. 34, and which is stabilized by the oscillator 34.

Fig. 3 shows a further modification of the present invention in which the same principles are applied to yet another type of velocity variation oscillator 46 known as the Monotron, which is described more fully in Hansen et al. Patent No. 2,269,456, issued Januar 13, 1942. In this type of oscillator, the electron beam from cathode I2 is projected into a hollow cavity resonator 41 through grid 13 by means of the accelerating voltage derived. from battery 33. The transit time of the electron beam within the resonator 41 is selected and adjusted in accordance with the principles set forth-in the above-mentioned Patent 2,269,456, to set up oscillations within the resonator 41. These oscillations may be fed to any suitable load device by means of .a coupling line 44. The frequency stabilizing and multiplying features of Figs. 1 and 2 may also be applied to the oscillator 46 of Fig. 3, by impressing the relatively low frequency voltage derived from oscillator 34 between the cathode l2 and grid l3 of oscillator 46, whereby the output of oscillator 46 is again stabilized at a harmonic of the output of oscillator 34. It will be noted thata slightly different coupling for low frequency oscillator 34 is used. However, this is equivalent to and interchangeable with that of Figs. land. 2.

In addition to the frequency multiplication provided by the devices of Figs. 1, 2 and 3, a n additional stage of multiplication may be incorporated in the device, in the manner'show n in Fig. 4. Thus, in this figure, there is shown the same type of oscillating and frequency multiplying system as in Fig. 1. However, the electron beam passing through grid I9, instead of being collected by collector 29 as in Fig. 1 is passed through the grids 5| and 52 of a further resonator 53 whose resobetween oscillator 34 and cathode I2.

. 2,281,935, issued May 5, 1942, the output ultra high frequency energy derived from resonator 53 by way of coupling line 28' will be harmonically related to the frequency of oscillations produced in resonators I6 and 2| which, as already discussed with respect to Fig. l, is in turn harmoni cally related to the output of oscillator as. In this way, a double frequency multiplication may be provided in a single device providing still higher frequencies while maintaining the same frequency stability.

Fig. 4 also shows a different form of coupling In this instance, the output of the oscillator 34 has one terminal grounded and the other terminal con nected directly to cathode I2 through a coupling and blocking condenser 38. The choke coil 39 in series with battery 33 prevents the alternating voltage on cathode I2 from being short-circuited to ground through battery 33. This coupling may be used interchangeably with the preceding couplings of Figs. 1 to 3.

Still another form of the present invention is shown in Fig. 5, where the same principle is shown applied to a velocity variation device of the type 7 shown in Hansen et al. Patent No. 2,259,690, issued :October 21, 1941, and termed a floating kidney device. In this device, the two resonators I 6 and 2| of Fig. l are merged into a single resonant space 55, by suitably suspending the drift tube I'I" within an outer envelope 56. Electrons projected from cathode I2 are velocity varied as they pass between grids I3" and I4, become grouped during passage along drift tube I1, and give up ultra high frequency energy to the field of resonator 55 upon passage through grids I8" and I9.

The relatively low frequency wave from oscillator 34 is again impressed between cathode I2 and grounded entrance grid I3" together with the accelerating voltage from battery 33, and the same type of operation ensues, to produce a frequency-multiplied and stabilized output at line 57.

. In each of the preceding figures the relatively low frequency voltage has been applied between cathode I2 and the entrance grid I3, I3 or I3" of the resonators of Figs. 1 to 5. Fig. 6 shows an alternative way of applying this relatively low frequency voltage, applicable with any of the elec tron beam devices of Figs. 1 to 5. In this figure, an added control grid 58 is inserted between the cathode I2 and the entrance grid I3, I3 or I3" of any of the modifications of Figs. 1 to 5, and the relatively low frequency voltage from oscillator 34 is connected between cathode I2 and grid 58, as by way of transformer 36 or any other suitable connection. The principle of operation of the devices of Figs. 1 to 5, modified as in Fig. 6, is exactly the same as that already described, and will produce the same results.

Fig. '7 shows a further modification applicable to any of Figs. 1-5. Here the relatively low frequency energy from oscillator 34 is led through a concentric line or other conductor 6| to a resonant cavity 62 preferably tuned to the frequency of oscillator 34. Resonator 52 is formed to provide a relatively narrow gap 63, between cathode I2 and the entrance grid I3, I3 or I3" of any of the resonators of Figs. 1 5. Cathode I2 is insulated from resonator 62 but is capacitively coupled thereto by way of sleeve 64 connecting cathode I2 with reentrant pole 65 of resonator 62 in a high frequency sense only, whereby the direct potential of battery 33 may be applied to cathode I2 despite the grounding of resonator 62 and without impairing the action of the resonator.

6 Resonator 62 operates functionally the same as tuned circuit 31, and the use of the modification of Fig. 7 with any of the devices of Figs. 1-5 will produce the same results already described above.

Thus, it will be seen that there has been provided an improved and novel apparatus for producing ultra high frequency energy having a frequency harmonically related to a relatively low control'frequency and stabilized by the low frequency source.

As 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:

1. Ultra high frequency apparatus comprising means for producing a beam of electrons, means in said apparatus including a circuit having a predetermined resonant frequency for periodically varying the velocity of the electrons of said beam and for utilizing said velocity-varied electrons for producing oscillations, and means including means along the beam path for modulating on said beam before said velocity-variation for controlling said beam at a frequency substantially sub-harmonically related to said first-named frequency, whereby frequency stabilized energy harmonically related to said controlling frequency may be obtained.

2. Ultra high frequency apparatus comprising means for producing a beam of electrons, means including means along the path of said beam for varying said beam at a predetermined frequency, self-oscillating electron-beam-utilizing means along the path of said beam for producing oscillations at an operating frequency substantially harmonically related to said predetermined frequency, said self-oscillating means being energized by said varied beam, whereby frequency stabilized energy harmonically related to said predetermined frequency is produced.

3. Ultra high frequency apparatus comprising a cavity resonator having a pair of electronpermeable walls, a cathode on one side of said resonator, a reflector electrode on the other side of said resonator, means in said apparatus for projecting an electron stream from said cathode through said resonator by way of said electronpermeable walls toward said reflector electrode, said means comprising a source of accelerating potential between said cathode and said resonator, means coupled to said cathode and said resonator for varying said potential at a frequency substantially subharmonically related to the resonant frequency of said resonator, and means coupled to said resonator for extracting high frequency energy at a harmonic of said subharmonic frequency from said resonator.

4. High frequency apparatus comprising a cavity resonator having an electron-permeable wall, a cathode opposite said wall, a second cavity resonator having said wall as a portion thereof and capacitively coupled to said cathode, the resonant frequency of said second resonator being substantially subharmonically related to that of said first resonator, means coupled to said resonator for projecting an electron stream from said cathode through said second resonator and said wall, and into said first resonator, and means coupled with said apparatus for excitin tially subharmonically related to said first resonator resonant frequency, whereby energy may be taken from saidflrst resonator at a harmonic of said exciting frequency.

5. A velocity modulation electron beam vacuum tube having a cathode, a control grid, a repeller electrode and a plurality of grids connected to a cavity resonator, a source of potential connected between said cathode and said resonator, a source of potential of lower value connected between said cathode and said repeller electrode, a source of high frequency energy connected to said grid, said source of high frequency energy being a sub-multiple of the resonant frequency of said resonator.

6. A velocity modulation vacuum tube having acathode, a control grid, a repeller electrode, and a plu1a1ity of grids connected to a cavity resonator, a source of potential connected to said resonator and said repeller electrode, means connected with said source for adjusting the potential of the repeller electrode to a value less than that applied to said resonator, and a source of high frequency energy connected between said grid and another point of said vacuum tube, said resonator being tuned to a high harmonic of the frequency supplied by said source of high frequency energy.

7. The method of generating harmonics with a velocity modulation vacuum tube having a cathode, a control grid, a repeller electrode, and a cavity resonator, comprising applying a direct current potential between said cathode and said resonator, applying a direct current potential of lesser value between said cathode and said repeller electrode, and applying to said cathode high frequency energy which is a sub-multiple of the resonant frequency of said resonator.

8. The method of generating harmonics with a velocity modulation vacuum tube having a cathode, a control grid, a repeller electrode, and a plurality of grids connected to a cavity reso- 8 nator, comprising applying a certain direct current potential between said cathode and said resonator, applying a direct current potential of lesser value than said certain direct current potential between said cathode and said repeller electrode, applying between said grid and said cathode high frequency energy, and adjusting said resonator to a frequency which is a higher harmonic of the high frequency energy applied to said grid.

9. A method of generating harmonics with a velocity modulation vacuum tube having a control grid, a repeller electrode, and a. cavity resonator, comprising applying a direct current potential between the cathode of said tube and said resonator, applying a direct current po. tential of lesser value to said repeller electrode, applying between said grid and another electrode of said vacuum tube high frequency energy, and adjusting said resonator to a frequency which is a higher harmonic of the energy applied to said grid.

WILLIAM W. HANSEN.

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

UNITED STATES PATENTS Number Name Date 2,067,366 Whitaker 'Jan. 12, 1937 2,075,112 Harmon Mar. 30, 1937 2,200,986 Fraenckel May 14, 1940 2,222,899 'Fraenckel Nov. 26, 1940 2,237,878 Haeff Apr. 8, 1941 2,245,627 Varian June 17,1941 2,250,511 Varian July 29, 1941 2,280,026 Brown Apr. 14, 1942 2,280,824 Hansen et a1 Apr. 28, 1942 2,281,935 Hansen et a1 May 5, 1942 2,293,151 Linder Aug. 18, 1942 2,350,907 Kroger June 6, 1944 2,401,945 Linder June 11, 1946

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