Coupled resonator slow wave structures for millimetric wave TWT

TWT based on coupled resonator slow wave structure (SWS) is capable of handling high peak and average power with higher efficiency and hence well suited for high power millimetric wave applications. In this paper, three different types of coupled resonator structures are discussed that can be used for millimetric wave TWTs. The three types are namely, Square coupled cavity SWS (CC SWS), inductively loaded inter-digital (ILID) SWS and inverted slot mode (ISM) SWSs, which operate in cavity mode, coalesced mode and slot mode respectively. All the three structures have been designed at W-Band and they are compared to find out the suitability of the structures for high power, wide bandwidth operation at mm wave frequencies. ILID structure gives 14.2% greater interaction i mpedance whereas ISM structure gives 18.96% lower interaction impedance when compared with square double staggered CCSWS. It was also found that ILID SWS gives an improved bandwidth by 4.08% and ISM SWS gives 5.2% more bandwidth as compared to square CCSWS.