RU2516874C1 - Travelling-wave tube - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: travelling-wave tubes (TWT) based on the principle of permanent long-term interaction of the electron stream with the travelling field in a non-resonance oscillation system can be used in different communications electronics equipment. TWT contains an electron gun, a slow-wave structure that consists of the circuit of coupled resonators with sealed dielectric partitions separating the slow-wave structure from SHF links, a focusing system as a number of electric or permanent magnets and a collector. The input and output resonators of the slow-wave structure are coupled with the wave-guide ducts through slots in the end walls. Matching with SHF wave-guide ducts is carried out due to increase in size of the coupling slots at the input and output resonators, change in their diameters and selection of angle α in the wave-guide ducts between the lower edge of the coupling slots and the opposite wall of the wave-guide duct and is made by calculation or by an experiment.

EFFECT: simplifying matching with SHF wave-guide ducts.

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Description

FIELD OF THE INVENTION

The invention relates to the field of microwave technology. Lamps of a traveling wave, based on the principle of continuous long-term interaction of the electron beam with the field of a traveling electromagnetic wave in a non-resonant oscillatory system, can be used in various electronic equipment.

State of the art

The development of multi-purpose radar for long-range tropospheric and space communications of modern means of radio-electronic suppression (REP) of information channels of weapon control systems requires the creation of broadband amplifiers of high-frequency microwave oscillations of more than 100 watts.

The most promising electrovacuum devices that make it possible to create such amplifiers are O-type traveling-wave lamps with longitudinal electric and magnetic fields. Due to the interaction of the electron beam distributed over the length with the electromagnetic field of the traveling wave in devices of this type, significant gain is achieved with a relatively small beam current. Gain factors, if necessary, can reach 60 dB or more. The use of slow-wave systems with weakly pronounced resonant properties provides amplification in a wide frequency band reaching two or more octaves. Powerful TWT continuous and pulsed modes are among the fastest growing group of microwave devices. A wide band of amplified frequencies is most easily achieved by using spiral decelerating systems. In the transition to average powers of the order of kilowatts or more, one has to switch to resonator moderating systems, which when used in TWT always give a smaller band of amplified frequencies (usually not more than 10%). In modern powerful TWTs, the most commonly used slowing systems are in the form of chains of resonators with inductive coupling made in the form of a diaphragmed circular waveguide. Neighboring resonators are interconnected through slots cut in the diaphragms. To obtain the limiting parameters in terms of power and efficiency, amplification chains consisting of a preamplifier (TWT) with a large gain and an output “transparent” TWT without absorbers with a small gain (7-15 dB) were also widely used. In a “transparent” TWT, resonator slowdown systems are also most often used.

A powerful TWT usually contains a retardation system in the form of a chain of coupled resonators with inductive coupling. The electron stream is created by an electron gun. In a retarding system, the kinetic energy of electrons is converted to microwave energy. After passing through a slowing system, the "spent" electronic stream enters the collector. The first and last resonators of the retardation system are used to input the transmitted microwave signal and output the amplified signal, respectively, and are connected with waveguide microwave paths. Sealing dielectric partitions separate the evacuated retardation system from the non-evacuated microwave paths. The magnetic field that focuses the electron beam is created by a magnetic system consisting of a series of electric or permanent magnets.

For TWTs with a retardation system in the form of a chain of coupled resonators, the problem of matching the latter with transmission lines is one of the most urgent. It is extremely difficult to get good retardation between the transmission system and the transmission lines in the working bandwidth, especially at its borders. Therefore, there is a risk of internal feedback due to the reflection of the electromagnetic wave at the ends of the slowdown system, especially at the boundaries of the working passband. At the same time, TWT can stop fulfilling its functions and become self-excited. To eliminate self-excitation, either selective absorbers (for example, from ceramics of the KT-30, AN-35Zh, PMK, AN-MKH brands.) Are placed in the retarding system, which introduce losses in limited areas of the working bandwidth of the retarding system (near the boundaries of the strip), or distributed film absorbers (e.g. alsifer film).

Powerful TWT is described in the book by Katsman Yu.A. "Microwave devices. Theory, fundamentals of calculation and design of electronic devices": Textbook for universities on special. "Electronic devices". - 2nd ed., Revised. and add. - M .: Higher. Shk., 1983.- 368 p. This TWT can be considered as a prototype. It contains an electron gun, a retardation system consisting of a chain of coupled resonators, sealing dielectric partitions separating an evacuated retardation system from non-evacuated microwave paths, a focusing system in the form of a solenoid, and a collector cooled by water. The input resonator of the retarding system with screws for adjusting the matching and the output resonator with the matching diaphragm form the so-called matching devices. Absorbers with matching rings are installed in the middle part of the retarding system. Adjustment of matching with screws can only work in a very narrow frequency band, since the screws adjust the frequency of the input resonator within small limits. Therefore, with screws, it is possible to improve the matching performance only in a very narrow frequency band. The input (output) resonator is connected with the waveguide paths from the side of the cylindrical cavity wall, which significantly complicates the matching process (obtaining the minimum value of the standing wave coefficient of the VSWR). The main reason is the significantly different electromagnetic fields in the region of the coupling gap between the resonators of the decelerating system and in the region of the coupling gap of the input (output) resonator and the waveguide path. It is impossible to “separate” the reflections from the connected waveguide and the reflections from the elements of the slowing system. All this is one of the main reasons for the use of absorbers inside the retardation system.

Ensuring the coupling of the input (output) resonator with the waveguide paths from the side of the end walls of the input and output resonators will make it possible to create almost identical conditions for the interaction between the waveguide path and the input (output) resonators and between the resonators of the retardation system and significantly simplify the process of matching the retardation system.

SUMMARY OF THE INVENTION

An urgent problem is obtaining good agreement between the slowing system and the transmission lines (obtaining the standing wave coefficient of VSWR ≤1.5) in the working bandwidth of the slowing system.

The indicated problem is solved as follows. A powerful LEV contains an electron gun, a slowing-down system in the form of a chain of coupled resonators, a magnetic system, a collector, and input and output short-circuited waveguides with sealing dielectric partitions.

The electron stream is created by an electron gun. Passing through the retardation system, the beam is braked and transfers part of the energy to the electromagnetic field, and the unused part of the beam enters the collector. The input and output waveguides associated with the slowdown system through the slit, and sealed from the microwave paths by sealing dielectric partitions, serve to input the transmitted microwave signal and output the amplified signal, respectively. The magnetic field that focuses the electron beam is created by a magnetic system consisting of a series of electric or permanent magnets.

The connection of the input and output resonators with the waveguide paths through the slot in the end wall will greatly simplify the task of obtaining good coordination (VSWR ≤1.5) in the working bandwidth of the slow-wave system. To eliminate reflections from the shorted segment of the waveguide, the waveguide wall opposite from the slit is connected to the lower edge of the communication slit by a truncated cone with an angle of inclination of the generatrix α, which is selected by calculation or experimentally.

From the point of view of the distribution of the electromagnetic field in the slowing-down system, the coupling elements (coupling gaps) with the waveguides will be in the same conditions as the gaps between the resonators of the slowing-down system. This will make it possible to apply a matching method that is simple in terms of implementation — increasing the coupling gap with the waveguide and adjusting the frequency of the input cavity.

List of drawings

Figure 1. A traveling wave lamp in which the input and output resonators are connected to the waveguide paths through slots in the end walls.

Figure 2. Slowing system of a traveling wave lamp, in which the input and output resonators are connected to the waveguide paths through slots in the end walls, and the waveguides end with a truncated cone with an angle α.

Figure 3. Estimated characteristic of the dependence of the magnitude of the VSWR on the frequency for a broadband slowdown system of a single-section traveling wave lamp.

Information confirming the possibility of carrying out the invention

The traveling wave lamp shown in FIG. 1 contains the following devices:

- electronic gun 1;

- a retarding system in the form of a chain of coupled resonators 2;

- magnetic system 3;

- collector 4;

- input resonator 5;

- output resonator 6;

- input shorted waveguide 7;

- output shorted waveguide 8;

- input sealing window 9;

- outlet sealing window 10.

The electron flux generated by the electron gun (pos. 1) propagates along the retardation system (pos. 2) and interacts with the longitudinal component of the electric field and the longitudinal focusing magnetic field created by electric or permanent magnets (pos. 3). Electrons in the process of interaction are modulated by speed, which leads to modulation of the flux in density. Due to the mutual connection between the field and the flow during its movement from the input of the slowing system to the output, this process increases, and the kinetic energy of the electrons is transferred to the field when they are braked. As a result of this process, the input microwave signal is fed into the input resonator (pos. 5) from the input shorted waveguide (pos. 7). The output of the microwave amplified signal is carried out from the output resonator (pos. 6) through the output shorted waveguide (pos. 8). The retardation system is separated from the microwave paths using sealing dielectric partitions (keys 9, 10). The "spent" electron stream enters the collector (item 4), where the kinetic energy of the electrons is converted into thermal energy.

Figure 3 shows the calculated dependence of the magnitude of the VSWR on the frequency for a broadband slowdown system of a single-section traveling wave lamp. The retardation system consists of thirteen resonators. The retardation system was matched with microwave paths by increasing the size of the coupling slits in the input and output cavities, changing their diameters and selecting the angle α. The working band of the retarding system is of the order of 20%, the value of VSWR in the working band is ≤1.5. The coordination results confirm the operability of the proposed design.

Claims (1)

 A traveling wave lamp containing an electron gun, a slowing down system consisting of a chain of coupled resonators, sealing dielectric partitions separating the slowing down system from microwave paths, a focusing system in the form of electric or permanent magnets and a collector, characterized in that the input and output resonators are connected to the waveguide paths through the slots in the end walls, and the waveguides end with a truncated cone with an angle of inclination of the generatrix α between the lower edge of the communication gap and the opposite wave wall water.

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