RU2714508C1 - Miniature multi-beam klystron - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: invention relates to miniature multi-beam klystrons used as power amplifiers of electromagnetic waves of short-wave part of centimeter and long-wave part of millimeter range of wavelengths in transmitters of radar stations, communication systems and in sources of microwave power, as well as in other radio equipment operating in pulsed or quasi-pulse modes. In miniature multi-beam klystron intended for operation in short-wave part of centimeter and long-wave part of millimeter range, containing electron gun, collector and electrodynamic system located between them, including intermediate resonators, input and output active resonators with input and output nodes of microwave energy, which include vacuum-dense dielectric microwave windows, consisting of round dielectric rods and outlet diaphragm with communication slits. At that, the miniature multibeam klystron also contains sections of input and output rectangular waveguides with passive resonators in the form of tuning pins made with possibility of changing their length, as well as tuning waveguide diaphragms, at least one of which is located between the first tuning pin, which is in close proximity to the end part of the dielectric rod, and subsequent tuning pins, adjusting waveguide diaphragms are made in form of plates bent in their middle part towards dielectric rods at angle of 45÷50 degrees, and the coupling gap, at least in the microwave energy output, is configured such that transverse dimensions of said slot are selected based on the provision for additional electromagnetic coupling between the output active resonator and the pre-output intermediate resonator.

EFFECT: broadening the amplification band of a low-voltage multi-beam broadband klystron without increasing the dimensions and weight of its input and output resonator systems while maintaining the level of output power, high reliability and quality of radio communication while maintaining thermal stability of the resonator unit.

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Description

The invention relates to miniature multipath klystrons used as power amplifiers for electromagnetic waves of the shortwave part of the centimeter and longwave parts of the millimeter wavelength ranges in radar transmitters, communication systems and in microwave power sources, as well as in other electronic equipment operating in pulsed or in quasi-pulse modes.

The main problem in creating multi-beam klystron microwave amplifiers is to obtain the widest possible gain band at a given level of output power, low supply voltages, and minimum weight and dimensions.

The expansion of the band of amplified frequencies is usually achieved by using passive resonators in the output klystron circuit [Copyright certificate SU 880158 A1, publ. 03/07/1992], forming a single filter system with an output active single-gap or double-gap resonator [US Patent 3484861 A, publ. 12.16.1969], [US Patent 3,299,312 A, publ. 01/17/1967].

For example, the transition to a two-loop filter system increases the relative frequency band at the level of 1 dB by 2.4 times, and to a three-loop filter - by 2.8 times [Pasmannik V.I. Connected loop systems. M .: Fizmatlit., 2005]. However, the structural and technological complexity in the manufacture of such a system in a multipath klystron significantly increase.

Known single-beam klystron [US Patent 3375397, publ. 03/26/1968], in the resonator system of which, consisting of a set of single-gap resonators, in order to increase the gain band and efficiency while maintaining the dimensions and mass, a direct electromagnetic coupling was introduced between the output and output active resonators using an axially symmetric coupling element made in a common wall for both resonators. Due to such an element of electromagnetic coupling in the passband of the resonance system, two closely spaced modes are excited corresponding to in-phase and out-of-phase modes of high-frequency electric field oscillations in the double gap. Moreover, in order to interact with the electron beam, as a rule, the in-phase (2π) mode of vibration is used. The optimal angle of flight between the centers of the gaps is selected from the conditions for achieving the maximum value of the effective characteristic resistance ρМ ² (where ρ = R / Q ₀ is the characteristic resistance in the main mode of vibration, M is the coefficient of interaction efficiency) and the absence of spurious self-excitation in the non-main mode of vibration. To fulfill the latter condition, it becomes necessary to forcefully reduce the quality factor of the resonance on the π-type of oscillations, since the connection between the inoperative type and the output path becomes small and its loaded quality factor tends to its own. The quality factor can be reduced, for example, by placing absorbing ceramics in the resonator region. However, this causes significant structural and technological problems when creating a multi-beam device designed to operate at extremely high frequencies.

The construction of a powerful single-beam S-band klystron is also known, in which two coupled active single-gap resonators (output and pre-output) were used as elements of a filter system [Z. Zhang, B. Shen, X. Yu, F. Zhu, Y. Han, Y. Huang, F. Zhang Development of an S-band 22-kW-averadge-power-klystron with 7.14% relative bandwidth. // IEEE Transaction on Electron Devices. 2011. Vol. 58, No. 8, pp. 2789]. To obtain a symmetric amplitude-frequency characteristic, the pre-output cavity was tuned to a higher frequency than the output cavity.

However, in this design, as well as in the previous analogue, there is a need to suppress spurious self-excitation by forcibly reducing the quality factor of an inoperative mode of vibration, which is not used for interaction with electrons.

A well-known design of a multi-beam miniature low-voltage klystron of 2 cm wavelength range, which uses the traditional method for klystrons to expand the band of amplified frequencies, based on the use of a passive resonator in the output klystron circuit, forming a single filter system with an output active two-gap resonator [Vostrov M.S. . Broadband miniature multi-beam klystron of 2 cm wavelength range with a working frequency band of at least 300 MHz and uneven output power of not more than 1.5 dB // Actual problems of electronic instrumentation APEP - 2018: materials of the 13th international scientific and technical conf., Saratov, September 27-28. 2018 - T. 1. S. 232-237].

In order to provide a passband of the output resonant system of at least 300 MHz, a double-gap resonator operating at the first spatial harmonic of the in-phase mode of vibration is used as an active output resonator in the klystron. It has a height of 3.4 mm and an angle of passage between the clearances of 5.6 radians.

However, the possibility of further increasing the operating frequency to 35-40 GHz while maintaining the output pulse power, the band of amplified frequencies, small dimensions and mass of the device is almost exhausted. This is due to the fact that with an increase in the frequency due to a decrease in the size of the resonators, the effective characteristic resistance of the output double-gap resonator ρМ ² sharply decreases and its resistance to thermal loads decreases. In addition, in order to maintain the gain band at 300 MHz, it is necessary to increase the number of passive resonators. At the same time, the mass and size characteristics of the klystron deteriorate, and the technological difficulties in manufacturing such a resonant system, which increase sharply when moving into the millimeter range, cause a low percentage of suitable devices and their high cost. Also, in a complex system of one active and several passive resonators of the filter system connected in series, it is difficult to ensure a minimum difference in the microwave power transfer coefficient from the active output resonator to the output path in a wide frequency band.

Closest to the claimed invention is the design of a broadband multi-beam klystron with a multi-link filter system [RF Patent No. 2645298, publ. 02/20/2018].

The klystron is designed to operate in the shortwave of the centimeter and longwave of the millimeter range. It contains an electron gun, a collector, and an electrodynamic system located between them, including intermediate resonators, input and output active resonators with microwave energy input and output nodes, which include: vacuum-tight dielectric microwave windows, consisting of round dielectric rods and diaphragms in which slots for coupling passive resonators with output and input active resonators are made; segments of the input and output rectangular waveguides with passive resonators in the form of tuning pins made with the possibility of changing their length, as well as with tuning waveguide diaphragms, at least one of which is located between the first tuning pin located in the immediate vicinity of the end part of the dielectric rod, and subsequent tuning pins.

Changing the length of the first tuning pin allows you to configure a rectangular waveguide with a dielectric inhomogeneity to the resonant frequency of the active output resonator or with a given offset from this frequency. However, in such a device, it is difficult to ensure, without the use of additional passive resonators, the minimum difference in the microwave power transfer coefficient from the input path to the input active resonator and from the output active resonator to the output path in a wide klystron frequency band. In addition, achieving a band of amplified frequencies in the Ku band of more than 1.5% at an output pulse power level of more than 500 W is difficult due to the small effective characteristic resistance ρМ ^{2 of the} output active single-gap resonator (of the order of 15–20 Ω).

The technical result of the present invention is to expand the gain band of a low-voltage multipath broadband klystron without increasing the size and mass of its input and output resonator systems while maintaining the output power level, increasing the reliability and quality of radio communications while maintaining the thermal stability of the resonator block.

The technical result is achieved by the fact that in a miniature multipath klystron designed to operate in the short-wavelength part of the centimeter and long-wavelength parts of the millimeter ranges, containing an electron gun, a collector and an electrodynamic system located between them, including intermediate resonators, input and output active resonators with input and output nodes Microwave energy, which includes vacuum-tight dielectric microwave windows, consisting of round dielectric rods and output diaphragm Agma with communication slots. Moreover, the miniature multipath klystron also contains segments of the input and output rectangular waveguides with passive resonators in the form of tuning pins made with the possibility of changing their length, as well as with tuning waveguide diaphragms, at least one of which is located between the first tuning pin located in the immediate proximity to the end part of the dielectric rod, and subsequent tuning pins, tuning waveguide diaphragms are made in the form of plates curved in the middle its parts to the side of the dielectric rods at an angle of 45 ÷ 50 degrees, and the coupling gap, at least in the output of microwave energy, is made so that the transverse dimensions of this gap are selected from the condition of providing additional electromagnetic coupling between the output active resonator and the pre-output intermediate resonator, and the distance between the centers of the gaps of these resonators S and the maximum longitudinal size of the slit L _max in the diaphragm are selected from the following relations:

d - длина зазора, м;

- длина пролетной трубы, м; β_е=2πƒ₀/ν₀ - постоянная распространения электронного потока, ƒ₀ - центральная частота полосы усиления, Гц; ν₀ - скорость электронного потока, м/с.where R is the radius of the dielectric rod, m;

d is the length of the gap, m;

- the length of the span pipe, m; β _e = 2πƒ ₀ / ν ₀ is the propagation constant of the electron beam, ƒ ₀ is the center frequency of the gain band, Hz; ν ₀ - electron flow velocity, m / s.

Another difference from the prototype is that the width of the coupling slit has a different shape at different distances from the center of the output resonator, so that in the region adjacent to the center of the gap of the output cavity, it has the shape of an ellipse, the large axis of which is oriented in the perpendicular direction with respect to the line passing through the centers of the gaps, and in the region adjacent to the center of the gap of the output cavity, the slit has the shape of a rectangle, the vertical side of which is equal to the distance between the foci of the ellipse; and the dimensions of the ellipse are selected from the following relationships:

where b is the semimajor axis of the ellipse, a is the semimajor axis, c is half the focal length.

Another difference from the prototype is that the resonant frequency of the pre-output intermediate resonator f _{5 is} selected higher by 3-4% in frequency than the frequency of the output active resonator f ₆ ; the resonant frequency of the tuning waveguide diaphragm corresponds to the frequency f _{n the} lower edge of the passband, and the resonant frequency of the dielectric rod f _c is located on the slope of the left branch of the amplitude-frequency characteristic.

These essential features distinguish the claimed solution from the prototype and determine the compliance of this solution with the criterion of "novelty."

The present invention allows, when working in the Ku-range, to approximately double the wide band of amplified frequencies without increasing the size and mass of its input and output resonator systems while maintaining the level of output power and thermal stability of the resonator block.

The invention is illustrated by drawings. In FIG. 1 shows a General view of the multipath klystron. In FIG. 2a shows a cross section of the output part of the klystron with a new configuration of the tuning waveguide diaphragm. In FIG. 2b shows the appearance of vacuum-tight dielectric microwave windows with segments of the input and output rectangular waveguides. In FIG. 3a shows the appearance of the output diaphragm, and FIG. 3b shows the cross-sectional shape of the communication slots in this diaphragm and its characteristic dimensions. The dependences of the interaction coefficient M and the relative electron conductivity Ge / Go on the angle of flight between the centers of the gaps of the output and pre-output cavities are shown in FIG. 4. This figure shows the optimal span selection angles for I and II (work area) spatial harmonics, respectively.

In FIG. Figure 5 shows the amplitude-frequency characteristic of the output resonance system experimentally obtained at the stage of “cold” measurements, confirming the expansion of the gain band. In FIG. 6 shows the experimentally measured amplitude-frequency characteristics (AFC) of the device: 1 - AFC of the device without a chain of passive resonators in the absence of electromagnetic coupling between the output active and pre-output intermediate resonators; 2 - frequency response of the device with a multi-link filter system at the output of the device in the presence of electromagnetic coupling between the output active and the output intermediate resonators (the resonant frequency of the dielectric rod f _c is on the slope of the left branch of the amplitude-frequency characteristic); 3 - frequency response of the device with a multi-link filter system at the output of the device in the presence of electromagnetic coupling between the output active and pre-output intermediate resonators (the resonant frequency of the dielectric rod f _c is in the center of the amplitude-frequency characteristic).

With reference to FIG. 1, FIG. 2 a-b, FIG. 3 a-b, FIG. 4, FIG. 5, FIG. 6 are indicated:

1 - electron gun;

2 - collector;

3 - intermediate resonators;

4 - input active resonator;

5 - output active resonator;

6 - node input microwave energy;

7 - node output microwave energy;

8 - round dielectric rod;

9 - output aperture;

10 - coupling gap of the input active resonator;

11 - coupling gap of the output active resonator;

12 - input rectangular waveguide;

13 - output rectangular waveguide;

14 - passive resonators in the form of tuning pins;

15 - tuning waveguide diaphragms;

16 - the first tuning pin.

The operation of the miniature multipath klystron is as follows. Using an electron gun (1), under the influence of an accelerating voltage, a multipath electron beam is formed, which is passed through channels for the passage of electron beams made in the input (4), intermediate (3) and output (4) active resonators. After the passage of the resonators, the electron beams are scattered on the collector (2).

The input microwave signal is supplied to a segment of a rectangular waveguide (12), which is part of the energy input unit (6), and excites in it an electromagnetic field of an H ₁₀ type wave, which, in turn, excites a multi-link broadband filter system consisting of passive resonators in the form of a tuning waveguide diaphragm 15 and a first tuning pin 16, forming together with a round dielectric rod 8 a tunable metal-dielectric resonator, the resonant frequency of which f _c tunes to the slope of the left branch of the amplitudes frequency response characteristics.

The excitation of the active input resonator occurs through a coupling slit 10, which provides additional electromagnetic coupling between the input active resonator and the second intermediate resonator. The width of the coupling slit has a different shape at different distances from the center of the input resonator. In the region of the second resonator, it expands. In this case, the loaded Q factor of the second resonator decreases and becomes approximately equal to the Q factor of the input active resonator associated with the load.

The distance between the centers of the gaps of these resonators is chosen from the condition of lack of self-excitation, which corresponds to positive values of the relative electronic conductivity of Ge / Go (Fig. 4).

When these conditions are met, the input resonant system provides excitation in the input double RF gap of the longitudinal electric microwave field of approximately the same intensity at all frequencies of the operating range of the klystron. The formation of dense electron bunches occurs when the electron beams pass sequentially through the intermediate resonators (3), where the electrons are additionally modulated by velocity, and drift tubes in which the electrons are modulated by density.

To create approximately the same amplitude of the first harmonic of the induced current in the output klystron oscillatory system at all frequencies of the working range using the frequency tuning mechanisms, the resonant frequencies of the intermediate resonators are adjusted accordingly (3). Passing through the gap of the output active resonator (5), electron bunches fall into the braking phase of the microwave field of the double RF gap formed between the output and pre-output resonators.

Due to the strong deceleration of the bunches by a high-frequency field, the electron velocity in this interaction region decreases by about 1.2-1.3 times in comparison with the region of the input resonator. This leads to an increase in the angle of flight. Therefore, in the output region, the distance between the centers of the gaps of these resonators is chosen from the condition of the absence of self-excitation corresponding to negative values of the relative electron conductivity Ge / Go (Fig. 4).

The optimal operating mode for implementing broadband amplification is the choice of the resonant frequency of the pre-output intermediate resonator f ₅ 3-4% higher in frequency than the frequency of the output active resonator f ₆ . In this case, the resonant frequency of the tuning waveguide diaphragm corresponds to the frequency f _{n of the} lower edge of the passband, and the resonant frequency of the dielectric rod f _c can be tuned to the slope of the left branch of the amplitude-frequency characteristic using the first tuning pin 16 (see Fig. 5). In this case, a single-band amplification mode is implemented with a wide band of amplified frequencies of more than 2%.

A tuning mode of the output filter system is also possible, in which the resonant frequency of the dielectric rod f _c can be mechanically (or electrically) tuned to the first operating pin in the gain band using the first tuning pin 16. In this case, the operation mode of the klystron in two closely spaced gain bands is possible (Fig. 6).

Since the design of the output filter system of the multi-beam broadband klystron is completely identical to the input, in it, thanks to the optimal shape of the coupling gap 11, electromagnetic waves are transmitted from the output active resonator through the energy output unit 7 to the output rectangular waveguide 13, connected by the load with a given transfer coefficient in the entire working klystron range.

The transition to a multi-link filter system consisting of a pre-output intermediate 3, an output active resonator 4 and passive resonators 14, 16 and tuning waveguide diaphragms 15 located in the energy output unit leads to the expansion of the gain band of this device (by about 2.8-3 times) without increasing its dimensions and mass.

Due to the fact that the proposed low-voltage klystron operates at the second spatial harmonic (zone II in Fig. 4), the heights of the pre-output intermediate and output active resonators, as well as the thickness of the partition between them, can be increased by about 1.5 times. This makes it possible to increase the effective characteristic resistance of these resonators in the short-wavelength part of the centimeter and millimeter wavelength ranges, where the dimensions of the resonators are small. Ultimately, this contributes to the achievement of a wide band, without increasing the dimensions and mass of the device, while maintaining the level of its output power of the order of 300-500 watts.

Sources of information

1. Copyright certificate SU 880158 A1, publ. 03/07/1992.

2. US patent 3484861 A, publ. 12/16/1969.

3. US patent 3299312 A, publ. 01/17/1967.

4. Pasmannik V.I. Connected loop systems. M .: Fizmatlit., 2005.

5. US patent 3375397 A, publ. 03/26/1968.A

6. Z. Zhang, B. Shen, X. Yu, F. Zhu, Y. Han, Y. Huang, F. Zhang Development of an S-band 22-kW-averadge-power-klystron with 7.14% relative bandwidth. // IEEE Transaction on Electron Devices. 2011. Vol. 58, No. 8, pp. 2789.

7. Vostrov M.S. Broadband miniature multi-beam klystron of 2 cm wavelength range with a working frequency band of at least 300 MHz and uneven output power of not more than 1.5 dB // Actual problems of electronic instrumentation APEP - 2018: materials of the 13th international scientific and technical conf., Saratov, September 27-28. 2018 - T. 1. -. S. 232-237.

8. RF patent No. 2645298, publ. 02/20/2018.

Claims (9)

1. A miniature multipath klystron containing an electron gun, a collector, and an electrodynamic system located between them, including intermediate resonators, input and output active resonators with microwave energy input and output nodes, which include vacuum-tight microwave dielectric windows, consisting of round dielectric rods and an output diaphragm with communication slots, characterized in that it further comprises segments of the input and output rectangular waveguides with passive resonators in the form of settings pins made with the possibility of changing their length, as well as with tuning waveguide diaphragms, at least one of which is located between the first tuning pin located in the immediate vicinity of the end part of the dielectric rod and the subsequent tuning pins, tuning waveguide diaphragms are made in the form plates bent in their middle part towards the dielectric rods at an angle of 45 ÷ 50 degrees, and the coupling gap, at least in the output of microwave energy, is made so that the transverse dimension s of this gap are selected from the condition of providing additional electromagnetic coupling between the output active resonator and the output intermediate resonator, and the distance between the centers of the gaps of these resonators S and the maximum longitudinal size of the gap L _max in the diaphragm are selected from the following relations:

where R is the radius of the dielectric rod, m;

d is the length of the gap, m;

- the length of the span pipe, m; β _e = 2πƒ ₀ / ν ₀ is the propagation constant of the electron beam, ƒ ₀ is the center frequency of the gain band, Hz; ν ₀ - electron flow velocity, m / s. 2. The miniature multipath klystron according to claim 1, characterized in that the width of the coupling slit has a different shape at different distances from the center of the output resonator, so that in the region adjacent to the center of the gap of the output cavity, it has the shape of an ellipse, the major axis of which is oriented in perpendicular to the line passing through the centers of the gaps, and in the region adjacent to the center of the gap of the output cavity, the slit has the shape of a rectangle, the vertical side of which is equal to the distance between the focuses of the ca, wherein the dimensions of the ellipse are selected from the following relations:

where b is the semimajor axis of the ellipse, a is the semimajor axis, c is half the focal length. 3. Miniature multipath klystron according to paragraphs. 1, 2, characterized in that for the implementation of the wideband amplification mode in one band, the resonant frequency of the pre-output intermediate resonator f _{5 is} selected 3-4% higher in frequency than the frequency of the output active resonator f ₆ , the resonant frequency of the tuning waveguide diaphragm corresponds to the frequency f _n the lower edge of the passband, and the resonant frequency of the dielectric rod f _c using the first tuning pin is tuned to the slope of the left branch of the amplitude-frequency characteristic. 4. Miniature multipath klystron according to paragraphs. 1, 2, characterized in that for the implementation of the two-way amplification mode, the resonant frequency of the dielectric rod f _{c is} tuned to a predetermined operating frequency located within the amplification band using mechanical or electrical tuning of the first tuning pin.

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