Abstract
In this paper, a novel angular log-periodic folded groove waveguide (ALFGW) slow-wave structure (SWS) has been investigated theoretically and experimentally for application in Ka-band traveling-wave tubes (TWTs). The dispersion relation for the ALFGW is derived analytically, and the dispersion characteristics are calculated for a Ka-band design. The designed SWS is fabricated using oxygen-free-copper that is silver electroplated. The measured cold-test parameters show good agreement with the simulation results, with S21 varying from −2.7 dB to −4.8 dB and S11 better than −13.6 dB over the frequency range of 30–38 GHz. Simulations of beam–wave interactions using a 4850 V and 0.4 A sheet beam with a high aspect ratio of 28:1 indicate an output power of 128 W, corresponding to a maximum gain and electronic efficiency of 18.1 dB and 6.6%, respectively. Due to the log-periodic form, a higher output power, higher efficiency, wider bandwidth, and lower operating voltage are achieved as compared to a TWT based on the conventional folded groove waveguide (FGW) SWS. These results show that the proposed ALFGW SWS has good potential for application in relatively high-power wideband TWTs.
Highlights
As our information society progresses, the need for electromagnetic signals of increasingly higher frequency and power becomes urgent.1,2 In the past few decades, traveling wave tubes (TWTs) have played a key role in fulfilling this need
These results show that the proposed angular log-periodic folded groove waveguide (ALFGW) slow-wave structure (SWS) has good potential for application in relatively high-power wideband traveling-wave tubes (TWTs)
IV, we show the results of beam–wave interactions to predict the performance of a TWT based on the ALFGW SWS and compare it with that based on a simple folded groove waveguide (FGW)
Summary
As our information society progresses, the need for electromagnetic signals of increasingly higher frequency and power becomes urgent. In the past few decades, traveling wave tubes (TWTs) have played a key role in fulfilling this need. Planar SWSs, such as microstrip, slot-line, and metallic meander line, offer low operating voltage and are easy to fabricate at high frequencies, and they accommodate a sheet electron beam. Between the folded waveguide and the folded groove waveguide SWSs, the latter is attractive since it allows the use of a sheet beam and has the potential to provide higher power.16,17 In this context, a novel angular log-periodic folded groove waveguide (ALFGW) SWS has been introduced by our group recently.
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