RU2530746C1 - Ultrahigh frequency cyclotron protective device - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: ultrahigh frequency cyclotron protective device includes an electron injector with a ribbon-type cathode, focusing and extraction electrodes, input and output cavity resonators having one-way communication to each other through an electron beam and separated with a membrane with a hole forming a transit-time channel, a collector and a device for creation of a homogeneous magnetic field coaxial with electron stream, the indication level of which provides for rotation of electrons at cyclotron frequency equal to average frequency of working frequency bandwidth of the device. Each resonator is connected and matched with external UHF-lines through a signal transmission circuit that is divided into parts (vacuum and non-vacuum) with trimming elements. A focusing electrode is made in the form of a rectangular plate located in front of a ribbon-type cathode along its length, the edges of which as to length are bent at a right angle to the cathode direction. A symmetry plane of a gap of an output resonator forms angle α with the central symmetry plane of the transit-time channel, with that, 3°≤α≤5°.

EFFECT: enlarging bandwidth of working frequencies of an ultrahigh-frequency cyclotron protective device of 3-cm wave length range.

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Description

The invention relates to the field of high-frequency radio electronics, and in particular, to devices for protecting microwave radio receivers, in particular, radar receivers, from exposure to a high level of input power in the centimeter and millimeter wavelength ranges.

In modern radar systems (radar), stringent requirements are imposed on the input stages of the receiver. Along with a small noise figure in the working frequency band, they must be reliably and efficiently protected from high-level microwave power with an extremely short recovery time after the microwave pulse ends. All these requirements are largely satisfied by cyclotron protective devices (CZU), operating on a fast cyclotron wave (BCV) of the electron beam.

It is known CZU according to the patent of the Russian Federation No. 2164480, which is based on the interaction of the electrodynamic structure with a central electron beam [1]. This device provides reliable protection from high-level microwave power with a short recovery time, however, it has a narrow band of operating frequencies in the signal transmission mode, comprising 2-4% in the 3-cm wavelength range. Limitations on the bandwidth of the working frequencies are due to two physical factors: insufficient electron loading of the resonators and poor quality of matching the conductivity of the electron beam and the electrodynamic structure with the conductivity of the external input and output microwave lines. The electronic load of the resonators of this device is limited by the values of current (100 ... 200 μA) and voltage of the resonator system (20 ... 40 V), within which stringent requirements on the level of current transmission (above 99%) are still fulfilled to ensure the required noise parameters of the central memory.

Closest to the proposed invention (prototype) is the central bank according to the patent of the Russian Federation No. 2453018 [2]. Its resonator system consists of input and output resonators having unidirectional communication with each other through the electron beam and separated by a diaphragm with a hole for the passage of the electron beam. The resonators are connected to external microwave lines by their signal transmission paths, each of which is divided by a dielectric window into vacuum and non-vacuum parts. In the non-vacuum parts of each path there are tuning elements (conductive protrusions in the form of pins or longitudinal plates), with which the operating frequency band is expanded to 6%. However, in many cases this value is insufficient due to the ever-increasing requirements for modern radars. Obviously, in order to further expand the working frequency band of the CZU, it is necessary to increase the electronic load of the resonator system by increasing the current (micropervance) of the tape electron flow, increasing the current density in the resonator gaps, narrowing the resonator gaps with the mandatory strict condition that the current flow in the CZU is above 99%.

An urgent problem in the development of the centrifugal and millimeter-wave DLCs is the expansion of the operating frequency band in the input mode of a low level by increasing the electronic load of the resonator system.

The technical result of the invention is the extension of the operating frequency band of a microwave frequency DZU 3-cm wavelength range.

The proposed microwave cyclotron protective device contains an electron gun with a tape cathode, focusing and pulling electrodes, input and output volume resonators having unidirectional communication with each other through the electron beam and separated by a diaphragm with an opening forming a passage channel, a collector and means for creating a uniform magnetic field coaxial with the electron beam, the level of induction of which ensures the rotation of electrons with a cyclotron frequency equal to the average frequency p the operating frequency band of the device, with each resonator connected and matched to external microwave lines by a signal transmission path, which is divided into parts, vacuum and non-vacuum with tuning elements. The focusing electrode is made in the form of a rectangular plate located in front of the tape cathode along its length, the edges of which are bent along the length at a right angle to the cathode. The symmetry plane of the gap of the output cavity forms an angle α with the central plane of symmetry of the passage channel, with 3 ° ≤α≤5 °.

The implementation of the focusing electrode in the form of a rectangular plate located in front of the tape cathode in the direction of electron motion along its length, the edges of which are curved along the length at right angles towards the cathode, allows us to provide the necessary cathode current and a smooth drop in current density along the edges of the cathode emitting surface. This leads to a decrease in the S-shaped distortion of the edges of the tape electron flow under the influence of its own space charge. The optimal distribution of current density along the cathode is achieved by supplying a negative (relative to the cathode) potential to the focusing electrode, a positive potential to the pulling electrode and their subsequent adjustment to a given current value and maximum current passage.

The location of the output resonator in such a way that the plane of symmetry of its gap forms an angle α in the range of 3 ° ≤α≤5 ° with the central plane of symmetry of the passage channel makes it possible to improve the current flow to the collector and increase the micropervance of the tape electron beam, i.e., increase the electronic load of the resonators and, consequently, expand its band of working frequencies of the central bank.

The invention is illustrated by drawings.

In Fig.1 shows a structural diagram of the proposed ZZU, which shows:

1 - electron gun,

2 - tape cathode,

3 - focusing electrode,

4 - a pulling electrode (first anode),

5 - input resonator,

6 - output resonator,

7 - tape electronic stream,

8 - diaphragm with a hole (span channel),

9 - collector,

10 - means (magnetic system) for creating a uniform magnetic field with an induction level of B ₀ ,

11 - signal transmission path to the input resonator,

12 - signal transmission path from the output resonator,

13 - the gap of the input resonator,

14 - clearance of the output cavity.

Figure 2 shows a schematic representation of an electronic gun of the proposed Central memory, where

2 - tape cathode,

3 - focusing electrode,

4 - a pulling electrode (first anode),

15 - heater (holder) of the cathode.

Figure 3 shows the results of computer simulation of the electron beam in the electron-optical system of the central memory - a prototype with twice the current of the electron beam.

Figure 4 shows the results of computer simulation of the electron beam in the electron-optical system of the proposed DLC with twice the current of the electron beam.

Figure 5 shows the experimental graphs of the frequency dependencies of the VSWR input (output) of the prototype device and the experimental sample of the proposed device 3 cm wavelength range.

An example of the implementation of the proposed device can serve as the design of the Central memory of the 3-cm wavelength range (see figure 1).

The device comprises an electron gun 1, a resonator system unit containing input 5 and output 6 volume resonators having unidirectional communication with each other through a tape electron stream 7 and separated by a diaphragm 8 with a rectangular hole for passage of the electron stream 7, a collector 9 and a magnetic system 10 for the formation of a longitudinal uniform magnetic field with induction B ₀ in the region of the resonators.

In the electron gun 1 along the coordinate axis Z, successively located one after another: a focusing electrode 3, a tape cathode 2 and a pulling electrode 4 (first anode). The input 5 and output 6 resonators with capacitive gaps 13 and 14 with centers in the planes Z1 and Z2 are separated by a transverse section in the form of a diaphragm 8 with a rectangular hole, which serves as a passage channel and provides unidirectional communication between the resonators through the electron stream 7. Input 5 and output 6 resonators are connected and matched with an external microwave line by their signal transmission paths 11 and 12, respectively. Trimmer elements in the form of pins and longitudinal plates are installed in their non-vacuum parts. In order to prevent possible electron deposition on the walls of the capacitive gap 14, the output resonator 6 is installed in such a way that the plane of symmetry of its capacitive gap 14 forms an angle α = 4 ° with the central plane of symmetry of the passage channel.

Figure 2 shows a schematic illustration of an electronic gun 1 of the proposed Central memory. The axes of the Cartesian coordinate system X, Y and Z are oriented respectively along the width and length of the emitting surface of the cathode and in the direction of electron motion. Elements 2, 3, 4 of the miniature design of the gun 1 are spaced along the Z axis for clarity of the picture. The tape cathode 2 is mounted on the holder 15, made in the form of a U-shaped frame made of round wire, which is also a cathode heater. The focusing electrode 3 has the form of a rectangular plate, the longitudinal edges of which are bent on two sides at right angles to the tape cathode 2. The focusing electrode 3 is installed in front of the cathode 2 and has a shielding effect on the three outer surfaces of the tape cathode 2 facing it. Narrow rectangular surface of the cathode 2 facing toward the pulling electrode 4 serves as an emitter. The pulling electrode 4 is the first anode of the electron gun 1 and is made in the form of a thin plate with a longitudinal rectangular hole oriented along the length of the cathode 2.

The proposed microwave supervisor is as follows.

In the transmission mode, the input signal enters the device from the external line through the input path 11 connected to the resonator 5. The electron gun 1 generates an electron stream 7, which passes through the gap 13 of the input resonator 5, the passage channel of the diaphragm 8, the gap 14 of the output resonator 6, and captured by the collector 9. The induction level B _{0 of a} uniform magnetic field provides the cyclotron frequency of rotation of the electrons in the long resonator gaps 13 and 14, approximately equal to the average frequency in the matching band of the resonators 5 and 6, n loaded with an electron beam 7, with external microwave lines. In the electron stream 7, an MFB of the electron stream is excited, which transfers signal energy from the input resonator 5 to the output resonator 6. From the output resonator 6, the signal is transmitted to the external microwave line through the output path 12.

The tape electronic stream 7 is formed as follows. Adjustable potentials from two independent power sources are supplied to the focusing electrode 3 and the first anode 4: the negative (with respect to the zero potential of the cathode) potential Ufoc of the focusing electrode 3 in the range of -50 V <Ufoc <0 and the positive potential Ua1 of the first gun anode in the range 0 <Ua1 <+50 B. By adjusting these potentials, the electric regime of gun 1 is adjusted to the required current (micropervance) of the electron beam 7 and the maximum current passage (above 99%).

The main difficulties in solving the problem of the qualitative formation of a thin high-performance ribbon electron stream are associated with perturbations of its cross section during its movement in a uniform longitudinal magnetic field [3]. They manifest themselves in the form of two simultaneously acting factors: an S-shaped bend of the edges of a tape electron stream of finite length and its monotonous rotation (rotation around the central axis of symmetry X = Y = 0 of the passage channel) as it approaches the collector. The combined effect of these factors reduces the current flow and limits the electronic load of the resonators.

The S-shaped distortion of the edges of the tape electron stream is due to the action of the space charge at the edges of the tape electron stream of finite length. In the proposed design of the electron gun by adjusting the potentials of the focusing and pulling electrodes, the optimal distribution of the density of the emission current along the length of the electron emitter is achieved: a constant current density in the central part of the emitter and gradually decreases to zero at the edges of the emitter. This weakens the action of the forces of the intrinsic space charge of the ribbon electron stream and the S-shaped distortion of its edges.

Rotation of the plane of symmetry of the gap 14 of the output resonator 6 by an angle α relative to the central plane of the passage channel in the diaphragm 8 reduces the deposition of electrons on the walls of its resonator gap, increases the current flow to the collector 9 and provides low noise parameters of the central memory. The numerical value of the range of variation of the angle α is obtained by computer simulation with the subsequent approximation of the results by an analytical expression:

α ° = kZ ₂ (P _µ t / w) ^1/2 (B ₀ / B _Br ) ^-1 , 5≤k≤7, where α ° is the angle between the symmetry plane of the capacitive gap 14 of the output resonator 6 and the central plane of symmetry of the span channel in aperture 8 (degrees). Z ₂ is the distance from the center of the emitting surface of the cathode 2 to the center of the capacitive gap 14 of the output resonator 6 (mm), P _µ is the micropereance of the tape electron flow 7 (μA / B ^3/2 ), t / w is the ratio of the width of the emitting surface of the cathode 2 to its length, B ₀ / B _Br - the ratio of the induction of the current B ₀ magnetic field to Brillouin B _Br (the value of the "margin" in the magnetic field).

The technical advantages of the proposed design of the central bank in comparison with the prototype are confirmed by computer simulation and experimentally.

Computer models and calculations were performed in the Cartesian coordinate system XYZ (see Fig. 1 and Fig. 2). The axes of the Cartesian coordinate system X, Y and Z are oriented, respectively, along the width t and length w of the emitting surface of the cathode 2 and in the direction of electron motion (see figure 2).

Figure 3 shows the results of computer simulation of the electron flow in the electron-optical system of the central memory of the prototype. In the assembled gun assembly of this device (with fixed interelectrode gaps), changes (increases) in the cathode current can be achieved only by changing (increase) the potential of the drawing electrode (the first anode of the gun) located at a fixed distance from the emitting surface of the cathode. Therefore, the distribution of the density of the emission current along the cathode is not controlled in this gun, which tends to increase at the edges of the cathode and increase the S-shaped distortions of the edges of the tape flow. To increase the electron flux current (micropervance) to the level I _о = 400 μA (P _μ = 4.47 μA / B ^3/2 ) in this device, the potential of the extracting electrode was set to Ua1 = + 9.5 B. The potentials of the resonators and collector were set to Uo = + 20 B and Ucol = + 250 V. Figure 3a shows the distribution of current density on the emitting surface of the cathode in the form of a volume mathematical surface S. The dimensions of the emitter (emitter length w and width t) are set relative to the cavity gap width d and are equal to w, respectively / d = 75, t / d = 2.2. On the left in FIG. 3, a black-and-white scale of current density is given, which allows determining the density of the emission current in the central part (1.5 A / cm ² ) and its increase to 2.2 A / cm ² at the edges of the emitter. Figure 3, b shows the trajectories of electrons (their projection onto the plane Z = 0) along the entire length of the formation of the electron beam in a uniform magnetic field with a magnitude of "margin" of ₀ / V _Br = 4.2, corresponding to a 3-cm wavelength range. It can be seen that the trajectories of the electrons located on opposite edges of the tape flow deviate in the direction of the X coordinate in mutually opposite directions, forming an S-shaped distortion of its edges. Figure 3, in the upper part of the figure shows the "trace" of the tape electron stream in the form of a current density distribution over its cross section in two Z planes: at the entrance to the gap (P5, input) and at the exit from the gap (P5, output) of the input resonator. In the lower part of the figure in Fig. 3, c, similar "traces" of the electron beam are shown at the entrance to the gap (P6, entrance) and at the exit from the gap (P6, exit) of the output resonator. It is seen that the perturbation of the flow structure due to the S-shaped distortion of the edges and the rotation of the entire ribbon stream leads to a partial deposition of electrons on the walls of the gap of the output resonator. The estimated value of the current flow to the collector in this case is 90%, in which the operation of the device is disrupted.

Figure 4 shows the results of computer simulation of the EOS of the proposed design of the central memory. At the same relative emitter sizes (w / d = 75, t / d = 2.2), to achieve twice the current value (I _о = 400 μA) and micropervance (P _μ = 4.47 μA / V ^3/2 ), the negative focusing potential was set electrode 3 (Ufoc = -43 V) and the positive potential of the pulling electrode 4 (Ua1 = + 9.5 V). The calculation of the formation of the tape flow 7 in the region of the resonator system was carried out in a longitudinal magnetic field with the same “margin” (B ₀ / B _Br = 4.2) for the 3 cm wavelength range and at the potentials of the resonators 5, 6 and aperture 8 (Uo = + 20 B) and collector potential 9 (Ucol = + 250 V). The angle between the symmetry plane of the gap 14 of the output resonator 6 and the central plane of symmetry of the passage channel in the diaphragm 8 was set equal to α = 4 °.

Figure 4a shows the distribution of current density along the length of the emitter: a uniform current density in the central part and its smooth decline along the edges of the emitter, which reduces the effect of the repulsive forces of the own space charge and the S-shaped distortion of the edges of the tape electron beam. Figure 4, b shows the projection of the electron trajectory, the plane Z = 0 in the region from the cathode 2 to the collector 9. At the top of figure 4, c shows the "traces" of the tape electron stream 7 at the entrance to the gap 13 (P5, entrance) and the output from the gap 13 (P5, output) of the input cavity 5. The “traces” of the flow at the entrance to the gap 14 (P6, input) and the output from the gap 14 (P6, output) of the output cavity 6 are shown below.

The obtained results of computer simulation confirmed 100% current flow to the collector 9 of the tape electron flow 7 in the proposed cyclotron device at twice the current (micropervance) compared to the prototype device.

The measurements of the frequency dependences of the VSWR input (output) were carried out on an experimental sample of the proposed design of the central memory, the results of which were compared with similar measurements on an industrial model of the prototype device.

The comparison results are shown in figure 5 in the form of graphs 1, 2, 3. The abscissa axis shows the frequency bandwidth (ff ₀ ) / f ₀ ,%, where f is the frequency of the input signal, f ₀ is the frequency of the input signal in the center of the working band frequencies. The bandwidth of the working frequencies was determined by the level of VSWR input (output), equal to 1.25.

Schedule 1 relates to a prototype device with standard values of current I _о = 200 μA and micropervance Р _μ = 2.23 μA / V ^{3/2 of the} electron beam doubled (compared with the proposed device) by the width of the resonator gaps and tuned signal transmission paths from the resonators to external microwave lines. In accordance with schedule 1, the working bandwidth of this prototype device is 6.4%.

Graphs 2 and 3 relate to the experimental model of the proposed cyclotron device. For the same current values I _о = 200 μA (micropervance Р _μ = 2.23 μA / V ^3/2 ) and all other conditions being equal, the operating frequency band in it increased to 7.8% (see graph 2). In addition, in the same sample, in full accordance with the above results of computer simulation, the current Io = 400 μA and the micropervance P _μ = 4.47 μA / V ^{3/2 of the} electron flow were doubled, and 100% current transfer to the collector was ensured. As a result of the increase in the electronic load of the resonator system, the operating frequency band in the proposed device expanded to 9.8%. (see chart 3).

Thus, the proposed design of the cyclotron protective device allows 1.5 times to expand the operating frequency band in comparison with the existing cyclotron prototype device 3 cm wavelength range.

Information sources

1. Patent of the Russian Federation No. 2164480, IPC Н02Н 7/12.

2. Patent of the Russian Federation No. 2453018, IPC Н02Н 7/00.

3. I.I. Golenitsky, N.G. Dukhina, E.I. Kanevsky. Comprehensive calculation of three-dimensional electron-optical and magnetic focusing systems of microwave electron-beam composites. Section 4. Tape electronic flow in the central memory. // Electronic equipment. Ser. 1. Microwave technology. Materials of the Jubilee Scientific and Technical Conference on Microwave Technology (FSUE NPP ISTOK, May 29-30, 2003, Part 2, Issue 2 (482). 2003, pp. 55-65.

Claims (1)

Microwave cyclotron protective device containing an electron gun with a tape cathode, focusing and pulling electrodes, input and output volume resonators having unidirectional communication with each other through the electron beam and separated by a diaphragm with an opening forming a passage channel, a collector and means for creating a uniform magnetic field coaxial with the electron beam, the level of induction of which provides the rotation of electrons with a cyclotron frequency equal to the average frequency of the working field the frequency axis of the device, with each resonator connected and matched to external microwave lines by a signal transmission path, which is divided into parts, vacuum and non-vacuum with tuning elements, characterized in that the focusing electrode is made in the form of a rectangular plate located in front of the tape cathode along its length, the edges of which are bent along the length at right angles to the cathode, the plane of symmetry of the gap of the output cavity forms an angle α with the central plane of symmetry of the passage channel, with 3 ° ≤ α≤5 °.

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