ABSTRACT
This paper proposed an X-band compact efficient rectangular waveguide TE10-circular waveguide TE01 mode converter and conducted its structure design, theoretical analysis, numerical simulation, and experimental research. This mode converter is composed of a rectangular waveguide TE10-TE20 mode converter and a rectangular waveguide TE20-circular waveguide TE01 mode converter. In the design of the rectangular waveguide TE20-circular waveguide TE01 mode converter, a rectangular waveguide step is used to counteract the microwave reflection due to the discontinuity of the rectangular-circular waveguide connection, and two choke slots are involved to suppress the TE21 mode in the circular waveguide by cutting off the axial component of its surface current on the waveguide wall, so as to improve the TE01 mode conversion efficiency. The simulation results show that the reflection coefficient of the mode converter is less than 5% and the TE01 mode conversion efficiency is about 98.4% at the operation frequency of 9.3 GHz. The bandwidth with a transmission coefficient greater than 98% is about 200 MHz. The back-to-back experimental system is demonstrated, and the experimental results show that the measured TE01 mode conversion efficiency is about 98.2%, which is consistent with the simulation result.
ABSTRACT
A novel T-shaped high-power waveguide phase shifter is investigated in this paper. The phase shifter consists of straight waveguides, four 90° H-bend waveguides, a stretching metal plate, and a metal spacer linked with the stretching metal plate. The entire structure for the phase shifter is symmetrical along both sides of the metal spacer. The phase-shifting principle for the phase shifter is to change the microwave transmission path by moving the stretching metal plate and then realize the linear phase adjustment. An optimal design approach of the phase shifter based on the boundary element method is described in detail. On this basis, a T-shaped waveguide phase shifter prototype with a center frequency of 9.3 GHz is designed. Simulation results show that the phase shifters can achieve 0°-360° linear phase adjustment by altering the distance of the stretched metal plate to 24 mm, and the efficiency of power transmission is more than 99.6%. In the meanwhile, experiments were conducted and the test results are in good agreement with simulation results. The return loss is more than 29 dB, and the insertion loss is less than 0.3 dB at 9.3 GHz in the entire phase-shifting range.
ABSTRACT
A high power microwave source based on energy storage switching pulse compression technology can produce a high power microwave pulse with good repeatability and frequency stability for a long time and has a good development prospect. In order to improve the power gain, this paper studies the working characteristics of the energy extraction structure of the X-band energy storage switching pulse compression device. The theoretical analysis results show that the impedance mismatch exists in the traditional energy extraction structure after the pulse compression is transferred to the energy extraction stage and the energy extraction efficiency is not high, which results in the power gain limitation. Therefore, through theoretical calculation and simulation, an improved scheme based on output inductance diaphragm is proposed in this paper. The scheme has high power capacity and can achieve impedance matching without changing the resonant frequency of the energy storage cavity, so as to improve the power gain of the pulse compression device. The high power experimental results show that the power gain of the pulse compression device can be increased from 6.24 times to 7.22 times and the energy extraction efficiency can be increased by 17.5% by placing 17 mm slot spacing inductance diaphragm at 45 mm of the H-T arm of the waveguide, which verifies the feasibility of the improved scheme.
ABSTRACT
A compact, high-directivity, weak-coupling directional coupler with coaxial-coplanar waveguide structure and diamond-shaped coupling slot was developed at L band for a high-power microwave measurement by both theoretical analysis and experiments. The relation between the dimension of the coupling slot and the characteristic parameters of the coupler was studied by the small-hole coupling theory and the infinitesimal method. According to the analysis results, the directivity could be better than 20 dB while the length of the slot is just less than a single λ because of the use of the diamond coupling slot. For demonstration, a 45-dB L band coaxial-coplanar waveguide directional coupler was designed and verified by test. The experiment results and the theoretical analysis are in good agreement, which indicates that in the range of 1-2 GHz, the coupling was approximately -45 dB and the directivity was better than 17 dB. The power-handling capacity was demonstrated to reach 2 MW with a length (150 mm) of less than λ and a cross section (46 mm × 55 mm) of less than one-twelfth of the BJ-14 waveguide directional coupler.
ABSTRACT
Based on measurement of the volume increment of polar liquid that is a result of heating by absorbed microwave energy, two types of calorimeters with coaxial capacitive probes for measurement of high-power microwave energy are designed in this paper. The first is an "inline" calorimeter, which is placed as an absorbing load at the end of the output waveguide, and the second is an "offline" calorimeter that is placed 20 cm away from the radiation horn of the high-power microwave generator. Ethanol and high density polyethylene are used as the absorbing and housing materials, respectively. Results from both simulations and a "cold test" on a 9.3 GHz klystron show that the "inline" calorimeter has a measurement range of more than 100 J and an energy absorption coefficient of 93%, while the experimental results on a 9.3 GHz relativistic backward-wave oscillator show that the device's power capacity is approximately 0.9 GW. The same experiments were also carried out for the "offline" calorimeter, and the results indicate that it can be used to eliminate the effects of the shock of the solenoid on the measurement curves and that the device has a higher power capacity of 2.5 GW. The results of the numerical simulations, the "cold tests," and the experiments show good agreement.
