A Ka-band TM02 mode relativistic backward wave oscillator with cascaded resonators

Abstract

By combining the Cerenkov-type generator with the cascaded resonators, this paper proposes a Ka-band relativistic backward wave oscillator operating under the guide magnetic field 1.0 T with high power handling capability and high conversion efficiency. It is found that TM 02 can be selected as the operation mode in order to increase the power handling capability and provide sufficient coupling with the electron beam. In slow wave structure (SWS), ripples composed of semicircle on top of the rectangle enhance the wave-beam interaction and decrease the intensity of the electric field on the metallic surface. Taking advantage of the resonator cascades, the output power and the conversion efficiency are promoted greatly. The front cascaded resonators efficiently prevent the power generated in SWS from leaking into the diode region, and quicken the startup of the oscillation due to the premodulation of the beam. However, the post cascade slightly postpones the startup because of the further energy extraction from the electron beam. The numerical simulation shows that generation with power 514 MW and efficiency 41% is obtained under the diode voltage 520 kV and current 2.4 kA. And the microwave with the pure frequency spectrum of 29.35 GHz radiates in the pure TM 01 mode. V C 2014 AIP Publishing LLC.

Influence of SWS Size on Mode Purification in an Overmoded Ka-Band Cerenkov Oscillator

“…Similar to the performance in Fig.3 (a), in each SWS, the field strength is growing with the increase of phase shift constant. Taking the position which is 2 mm away to the surface of SWS into consideration [14], [25], the field strengths at this position for all the harmonic waves are lined out by the dash lines in Fig.3 (b). According to the analysis in Fig.2, the non-synchronic points on TM 02 have the phase shift values from 0.29 π to 0.53 π when the overmoded ratio of SWS is increased from 1.8 to 2.7.…”

Control of the Operation Mode of a Relativistic <italic>Ka</italic>-Band Backward-Wave Oscillator

“…Such a slow-wave HPM sources with quasi-rectilinear beams (see [2]- [5], and the references therein) approach by peak power to the most complicated and powerful HPM devices like K a-band free-electron laser amplifiers [6] and K a-band and X-band multiwave and overmoded Cherenkov oscillators [7]- [10]. That is why, investigations of relativistic BWOs are promising to date [11]- [13]. The advantages of BWOs are their adaptability to variations in e-beam energy, short transient times, and high efficiency.…”

A 57GHz overmoded coaxial relativistic backward wave oscillator with high conversion efficiency and pure TM01 mode output

“…As L d satisfying the equation: 3 ωl d /v 0 = 8.69 (where ω is operating frequency and v 0 is the initial electron velocity), the electron beam entering the SWS2 is most favorable for beam wave interaction with the maximum bunching and minimum velocity spread. 5 At the operating frequency, the solution of the equation is 5.9mm. Such drift length can purify the output mode as well as ensuring ideal electron bunching.…”

“…Among various kinds of HPM sources, the relativistic backward-wave oscillator (RBWO), which is considered as one of the most promising HPM generators, are of great interests for its potential application in high-energy physics, high power radar, and satellite communication due to its high efficiency and compact structures. [1][2][3][4][5] Ref. 6 shows that coaxial SWSs have an advantage over hollow SWSs in achieving high power capacity (which describes the maximum transmission power in the SWSs under the limitation of breakdown field strength) and mode control simultaneously, especially in high frequency band.…”