An overmoded relativistic backward wave oscillator with efficient dual-mode operation

Compact circular waveguide TM 02 ‐TE 11 mode converter

“…HPM source plays an important role in HPM systems. The relativistic backward-wave oscillators (RBWOs), which are considered as one of the most promising HPM generators, have attracted more and more attention [3][4][5][6][7][8][9][10]. RBWOs operating in L-, S-, and C-bands often select TM 01 circular waveguide (Cir.TM 01 ) as an operation mode.…”

“…RBWOs operating in L-, S-, and C-bands often select TM 01 circular waveguide (Cir.TM 01 ) as an operation mode. However, as the HPM source has been developed gradually in high frequency, such as X-, Ka-bands, the conventional RBWOs which always operate in the Cir.TM 01 surface wave, is of smaller size and support less power-handling capability [3][4][5][6]. Compared with the Cir.TM 01 surface wave, TM 02 circular waveguide (Cir.TM 02 ) mode is considered as the volumetric wave remarked by higher power-handling capability [3][4][5][6].…”

“…However, as the HPM source has been developed gradually in high frequency, such as X-, Ka-bands, the conventional RBWOs which always operate in the Cir.TM 01 surface wave, is of smaller size and support less power-handling capability [3][4][5][6]. Compared with the Cir.TM 01 surface wave, TM 02 circular waveguide (Cir.TM 02 ) mode is considered as the volumetric wave remarked by higher power-handling capability [3][4][5][6]. In order to alleviate the explosive emission occurring on the slow wave structure (SWS) under the action of intense RF field and to increase the power-handling capability of the RBWOs, the overmoded SWS that operating at Cir.TM 02 mode is adopted [3].…”

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

“…In order to avoid mode competition, the electron beam should interact with the fundamental space harmonic of TEM mode (quasi-π mode) synchronously to realize transverse mode selection. [13][14][15] However, with surface SWSs, the TEM mode becomes surface wave, while the TM 01 mode is still volume wave. Obviously, since the power handling capacity of the volume waves is larger than that of the surface waves, the overmoded operation of TEM and TM 01 mode can gain higher power capacity than TEM single-mode operation.…”

“…In the dual-mode devices such as the 32GHz coaxial BWO proposed by Ref. 13 14) plays an important role in the high power microwave generation. According to this mechanism, we proposed a similar overmoded coaxial device in which the electron beam interacts synchronously with the fundamental mode (quasi-TEM mode).…”