CN106128914A - A kind of novel gyrotron traveling wave tube input coupler - Google Patents

Abstract

A kind of novel gyrotron traveling wave tube input coupler of this disclosure of the invention, belongs to microwave, millimetric wave device technical field.Including coaxial configuration, it is respectively arranged at ending circular waveguide and exporting circular waveguide and be arranged at the rectangular input waveguides of coaxial configuration side of coaxial configuration two ends, wherein being provided with several coupling gaps on coaxial configuration inner wire, rectangular input waveguides E face is provided with short circuit branch rectangular waveguide.The present invention, on the basis of tradition gyrotron traveling wave tube, arranges a short circuit branch waveguide in rectangular input waveguides E face.By position and the structural parameters of appropriate design short circuit branch waveguide, it is possible to the effective reflection offsetting input coupler, increase the efficiency of transmission of front end, thus effectively extension inputs bandwidth.

Description

A New Input Coupler for Convolutional TWT

technical field

The invention belongs to the technical field of microwave and millimeter wave devices, and in particular relates to a novel gyrotron traveling wave tube input coupler and a design method thereof.

Background technique

In the cyclotron traveling wave tube, the input electromagnetic wave interacts with the electrons in spiral motion. At this time, due to the influence of relativistic negative mass effect, the electron beams form angular clusters in the lateral direction, and continue to spiral forward to reach the high-frequency interaction. The area of effect falls into the deceleration field. In the high-frequency deceleration field, part of the energy of the electron injection is converted to the high-frequency field to realize the amplification of the high-frequency field, so that high-power microwaves and millimeter waves are obtained at the output end.

The gyrotraveling wave tube input coupler is a coupling input device. Its function is to convert the microwave signal output by the pre-amplifier into the working mode in the gyrotraveling wave tube through the mode conversion structure, so as to input the microwave signal into the gyrotraveling wave Tube. When the performance of the input coupler is poor, due to the high-gain characteristics of the gyrotron, not only the echo will cause certain damage to the pre-amplifier, but also the low purity of the input mode will have a relatively large impact on the output power, efficiency and gain of the gyrotron. Significant effects, severe cases will make the gyro TWT unable to work. Therefore, it is necessary to optimize the input coupler. The traditional gyrotron TWT input coupler is shown in Figure 5. It consists of a cut-off circular waveguide, an output circular waveguide, a coaxial structure, and a rectangular input waveguide. Several coupling slots are set on the inner conductor of the coaxial structure. The TE10 mode of the input signal is input from the rectangular input waveguide to the coaxial structure, the TE10 mode is converted into the TEmn1 mode in the coaxial cavity, and the TEmn1 mode is input into the output circular waveguide through the coupling gap of the conductor in the coaxial cavity, and the mode is converted by the TEmn1 mode The TE01 mode in the output circular waveguide is formed, so as to provide the circular waveguide TE01 mode required for the work of the convoluted traveling wave tube. However, this structure usually has large reflection and low transmission rate at the high end of the frequency band, resulting in narrow bandwidth. Can not meet the requirements of broadband.

Contents of the invention

In order to eliminate the reflection between the input rectangular waveguide and the coaxial cavity of the traditional gyrotron TWT input coupler, expand the bandwidth of the input coupler and increase the microwave transmission efficiency. The invention proposes a new type of convoluted traveling wave tube input coupler. On the basis of the traditional convoluted traveling wave tube, a short-circuit branch waveguide is arranged on the E surface of the rectangular input waveguide. By rationally designing the position and structural parameters of the short-circuit branch waveguide, the reflection of the input coupler can be effectively offset, the transmission efficiency at the high-frequency end can be increased, and the input bandwidth can be effectively expanded.

Concrete technical scheme of the present invention is as follows:

A new type of gyrotron TWT input coupler, the structure of which is shown in Figures 1 and 2. It includes a coaxial structure, a cut-off circular waveguide and an output circular waveguide respectively arranged at both ends of the coaxial structure, and a rectangular input waveguide arranged on the side of the coaxial structure, wherein the inner conductor of the coaxial structure is provided with several coupling slots, which are characterized in that : The E-side of the rectangular input waveguide is provided with a short-circuit branch rectangular waveguide.

The TE10 mode of the rectangular waveguide is used as the input signal to enter between the inner and outer conductors of the coaxial structure from the rectangular input waveguide, and the signal mode is transformed from the TE10 mode of the rectangular waveguide to the TE411 mode in the coaxial cavity. The coaxial TE411 mode is input into the output circular waveguide through the coupling gap of the inner conductor of the coaxial structure, and the mode is transformed into the circular waveguide TE01 mode at the same time, and the output circular waveguide provides the required TE01 mode input signal for the convoluted traveling wave tube.

When the input signal of the rectangular waveguide in the background art is input into the coaxial cavity, reflection is inevitably generated due to the change of the structure form, which reduces the input coupling efficiency, which has a significant impact on the output power, efficiency and gain of the gyrotron. At the same time, the bandwidth may be reduced and the flatness of the gain in the band may be reduced. In severe cases, the TWT may not work. The present invention arranges the short-circuit branch waveguide on the wide side of the rectangular waveguide, and uses the principle of equal-amplitude anti-phase superposition to make the coaxial reflected wave and the reflected wave of the rectangular short-circuit branch cancel each other, thereby reducing the reflected wave from the coaxial structure and achieving the improvement Mode purity, beneficial effect of extending operating bandwidth.

Compared with the traditional gyratory traveling wave tube input coupler, the present invention introduces a short-circuit branch waveguide to absorb the reflected wave of the input signal; by adjusting the length of the narrow side of the short-circuit branch waveguide, the longitudinal length and the distance from the coaxial cavity, the reflection waveguide is satisfied. The condition of phase reversal and equal amplitude of the wave and the wave of the short-circuit branch waveguide, so as to absorb the reflected wave, and then realize the broadening of the working frequency band.

Description of drawings

Fig. 1 is a front view of a section view of an input coupler for a gyrotron traveling wave tube provided by the present invention.

Fig. 2 is a top view of a cross-sectional view of the input coupler of the gyrotron traveling wave tube provided by the present invention.

Fig. 3 is a schematic diagram of the principle of the input coupler of the gyrotron traveling wave tube provided by the present invention.

Fig. 4 is a comparison diagram of S11 parameters obtained from tests of the new gyro TWT input coupler provided by the embodiment of the present invention and the conventional gyro TWT input coupler.

Fig. 5 is a schematic diagram of a three-dimensional model of a traditional input coupler structure of a gyrotron TWT.

detailed description

Below in conjunction with design example and accompanying drawing, the present invention will be described in further detail.

This embodiment provides a convoluted traveling wave tube input coupler working in the Ku band and TE01 mode, and its technical specification requirements are as follows:

Main waveguide working mode: circular waveguide TE01 mode.

Input signal mode: rectangular waveguide TE10 mode.

Working frequency band: Ku band, namely 12.4GHz-18GHz.

Standard rectangular waveguide model: BJ180, wide side size 12.954 mm, narrow side size: 6.477 mm.

The structure of the input coupler of the gyrotron traveling wave tube provided in this embodiment is shown in Figure 1 and Figure 2. The main structure and specific dimensions are as follows: 1 is a coaxial cavity structure, the inner radius of the inner conductor is 12.3mm, and the thickness is 0.5mm , the inner radius of the outer conductor is 16mm, and the length of the gap between the inner and outer conductors is 14mm; 2 is the cut-off circular waveguide, the radius is 10mm, and the length is 10mm; 3 is the output circular waveguide, the inner radius is 12.3mm, and the length is 21.88mm; 4 For the input rectangular waveguide, the standard rectangular waveguide model BJ180 is used, the wide side is 12.954mm, the narrow side is 6.477mm, and the length is 20.33mm; 5 is the short-circuit branch waveguide, the wide side is 12.954mm, the narrow side is 4mm, and the length is 16mm; 6 is the inner conductor coupling gap , width 0.8mm, length 8mm, distance from the upper and lower edges of the coaxial inner conductor is 3mm, a total of 4 coupling slots, the angle between the first coupling slot and the center of the rectangular input waveguide is 45 degrees, the angle between adjacent coupling slots is 90 degrees.

Suppose the phase of the wave coming out from point A and returning to point A after being reflected by the coaxial inner conductor is but

The reflection field E1 generated at the coaxial structure can be expressed as

The phase when the wave enters the short-circuit branch waveguide and returns to point A is set to

The reflection field E2 in the short-circuit branch waveguide can be expressed as

To enhance the transmission and reduce the reflection, it is necessary to

E1+E2＝0 ⑸

If the reflected wave cancels the outgoing wave of the branch waveguide, the phase condition is

The amplitude condition is

Er1＝Er2⑺

in, is the phase of the electromagnetic wave emitted from point A and returned to point A after being reflected by the coaxial inner conductor, k _z1 is the propagation constant of the rectangular input waveguide, L ₁ is the distance from point A to the coaxial structure electromagnetic wave propagation, θ is the wave in the coaxial The angle of the phase shift generated when the structure reflects, k _z2 is the propagation constant of the short _- circuit branch waveguide, L2 is the length of the short-circuit branch waveguide, and ω is the angular frequency of the electromagnetic wave. Er1 is the magnitude of the reflection field generated at the coaxial structure, and Er2 is the magnitude of the reflection field in the short-circuit branch waveguide. is the phase when the electromagnetic wave enters the short-circuit branch waveguide and returns to point A.

Er1 is determined by the established coaxial structure and cannot be changed. Er2 is determined by the value of the narrow side width b of the short-circuit waveguide. The design can meet the requirements of constant amplitude inversion by optimizing the value of narrow side width b.

The reflection coefficient test results of the new type of gyro-traveling-wave tube input coupler and the general-type gyro-traveling-wave tube input coupler provided in this example are shown in Fig. The reflection coefficient within 17.4GHz is greater than -8dB, of which the 2dB bandwidth is 1.96GHz, and the 2dB bandwidth of the traditional structure is 1.3GHz, which is about 50% of the bandwidth increase of the traditional structure; the 3dB bandwidth is 2.12GHz, and the 3dB bandwidth of the traditional structure is 1.66GHz , relative to the bandwidth increment of the traditional structure is about 27.7%.

Claims (1)

1. The utility model provides a novel travelling wave tube input coupler circles round waveguide and output round waveguide including coaxial structure, set up respectively in the ending at coaxial structure both ends and set up in the rectangle input waveguide of coaxial structure side, wherein is provided with a plurality of coupling gap, its characterized in that on the coaxial structure inner conductor: the E surface of the rectangular input waveguide is provided with a short-circuit branched rectangular waveguide.