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Experimental investigation and design of sectoral waveguide <i>TM</i> <sub/>01</sub> to <i>TE</i> <sub/>11</sub> mode converter
摘要： In this paper, an all-metal sectoral waveguide (SWG) mode converter has been proposed for TM01 to TE11 mode conversion, suitable for high-power application with high mode conversion efficiency and beam stability. Describing its operating principle, electromagnetic (EM) analysis has been carried out to observe the propagation behaviour in the different structure regions of the mode converter. A comprehensive design methodology, experimental investigation along with its beam stability performance has been presented. This design methodology has been typically demonstrated for 2.9–3.1 GHz frequency device; the performance of the designed device has been carried out using a commercial simulation code. To validate our design methodology and simulation, the results have been compared with experimental results and found in agreement. The proposed SWG mode converter has exhibited high conversion efficiency (98.4%) along with EM beam stability, suiting for the high-power applications.
关键词： mode converter,Sectoral waveguide,high-power microwave,SWG mode converter,HPM mode converter
更新于2025-09-19 17:13:59
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Theoretical Research on Properties of Spatial Harmonics in Corrugated Waveguide
摘要： This paper investigates the dependence of the properties of the spatial harmonics on the overmoded ratio of the corrugated waveguide operating in TM01 at 30 GHz with the consideration of the effects of the ripple shape. It is found that as the overmoded ratio grows, the electric ?elds concentrate towards the ripple surface, which weakens the enhancement of the power handling capacity caused by augmentation of the overmoded ratio. As the overmoded ratio grows, the ratio between the ?eld amplitudes of the ?1st spatial harmonic and the fundamental harmonic increases monotonically. Therefore, the total electric ?elds composed of the spatial harmonics become the spatial beating-wave with the single frequency, whose amplitudes vary along z-axis with the spatial period determined mainly by the ?1st spatial harmonic and the fundamental harmonic. Researches on coupling impedances show that with the same overmoded ratio, the corrugated waveguide consisting of the improved rectangular ripples provides better synchronous coupling for the wave-beam interaction than that of the sinusoidal ripples does. Moreover, it is better to choose the fundamental harmonic close to the light line as the synchronous wave for the wave-beam interaction in the low magnetic ?eld. In that case, even if the electron beam keeps far away from the ripple surface, the synchronous wave still provides strong enough coupling for the electron beam.
关键词： ?eld distribution,coupling impedance,high power microwave generation,Corrugated waveguide,overmoded ratio
更新于2025-09-16 10:30:52
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Analysis and design of TEM-TE11 coaxial waveguide bend mode converters
摘要： Two coaxial waveguide bend mode converters that transform coaxial transverse electromagnetic mode to TE11 coaxial waveguide mode are presented in this paper. Both converters are designed and optimized on the basis of the strictly derived mode coupling coefficients. Conversion efficiencies of both converters are over 99% and the power-handling capacities reach a gigawatt level. The combined dual-bend mode converter is fabricated and tested. The experimental results coincide well with the theoretical calculations and simulations, which demonstrates the feasibility of the designed converter.
关键词： Mode converter,high-power microwave,waveguide bend,mode coupling
更新于2025-09-11 14:15:04
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Relativistic microwave oscillators with high power flux in a free space and interaction zone
摘要： In the recent two decades, high-power microwave (HPM) generators producing short Ka-band and X-band pulses were intensively investigated (see Refs. [1–6] and citation therein). For generation of HPM pulses with duration of units of nanosecond and less influence of microwave breakdowns of electrodynamics systems, expansion of cathode and collector plasmas, and electron beam structure distortions becomes insignificant. Though the pulse duration is short, the radiating energy rises if coherent summation of radiation from several generators is provided. When the power in each channel is high, the wave beam could be formed where power flux density is limited only by breakdown strength of the media. Using approaches of the phased arrays, the directional pattern (DP) of summarized radiation could be steered. This is achievable from pulse to pulse, as well as during a single nanosecond pulse if summarized wave beams have a shifted frequencies. The related experiments with Ka-band microwave pulses are presented below.
关键词： directional pattern,Ka-band,phased arrays,superradiance,microwave breakdowns,backward-wave oscillators,X-band,coherent summation,high-power microwave
更新于2025-09-10 09:29:36
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Investigation of an $X$-Band Long Pulse High-Power High-Gain Coaxial Multibeam Relativistic Klystron Amplifier
摘要： Increasing the output power of the microwave is one of the most important development directions for high-power microwave (HPM) technology. However, when the output power is increased, the radio frequency breakdown would occur owing to superhigh electric field strength. This problem limits the power handling capability of a single-HPM generator, and this problem becomes more serious for high-frequency bands and long pulse. One solution to overcome this problem is coherent power combining, and coherent power combining can achieve an equivalent power of the order of TW. The relativistic klystron amplifier (RKA) is a promising candidate for coherent power combing owing to its character of controllable frequency and steady phase. However, the radiation power of RKA quickly decreases when the source is scaled up to higher frequencies such as X-band, and moreover, the multigigawatts long pulse radiation from RKA at the X-band has not yet been obtained experimentally. In this paper, we present investigations into an X-band coaxial multibeam RKA, The power handling capability was increased by introducing 20 electron drift tubes and a four gaps extended interaction output cavity. The amplitude uniformity of the multiple electron beams was improved by optimized the anode and cathode configuration. Then, a radiation power of 2.2 GW with pulsewidth of 120 ns is generated experimentally; the working frequency and amplifier gain are 9.4 GHz and 50 dB, respectively.
关键词： Coaxial multibeam relativistic klystron amplifier (CMB-RKA),X-band,long pulse,high-power microwave (HPM)
更新于2025-09-10 09:29:36
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A Ku-band coaxial transit-time oscillator with Pierce-like cathode under permanent magnet packaging
摘要： A novel Ku-band coaxial transit-time oscillator (TTO) with Pierce-like cathode is proposed in this paper. TTO has the characteristics of low space-charge effect and short interaction distance. Combining with these features, we design a novel Pierce-like cathode to lower the demand for the guiding magnetic field. The guiding magnetic field intensity is reduced to about 0.32T by loading the Pierce-like cathode, but the magnetic field intensity is not a stable value, it fluctuates at 0.32T because of the properties of permanent magnet. To achieve the light and small goals of TTO, we design a novel permanent magnet structure with NdFeB. Based on the research, the typical simulation result is that when the diode voltage is 440kV, the beam current is 11kA, the guiding magnetic field is about 0.32T, the device can output 1.46GW microwave pulse at 14.2GHz. The power conversion efficiency is about 30%.
关键词： coaxial transit-time oscillator,Pierce-like cathode,permanent magnet packaging,Ku-band,high power microwave
更新于2025-09-10 09:29:36
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Electromagnetic Wave Theory for Calculation of Exact Magnetic Field in Case of BWO
摘要： Overall efficiency of high power microwave generating device depends upon input current in the form of electron beam and currents required for electromagnets. In order to increase the efficiency of device, if electromagnets are replaced by permanent magnets, overall efficiency of device shall increase. So, calculation of exact magnetic field is required. In this paper, the exact relation of magnetic field required in high power microwave generation using Backward Wave Oscillator (BWO) is found. BWO interacts with slow waves and is the most promising device to produce high power microwaves. The interaction involves the beams from high current density and the waveguide mode. An exact relation that specifically relates the various parameters of the waveguide like slow wave structures (SWS) dimensions, input beam voltage and operational frequency with axial magnetic field is derived. The derived equation gives calculation of exact values of magnetic field for focusing of beams. Theoretical and simulated work show good agreement with the previously available experimental data. So, with the derived electromagnetic wave relation exact value of magnetic field is calculated for desired frequency and power regime.
关键词： High current electron,High power microwave,Wiggler,Magnetic field,Oscillator
更新于2025-09-04 15:30:14