طراحی یک آمپلی فایر لوله موج گذرا موجبر آبشاری باند V پرتوان جدید Design of a Novel High Power V-Band Helix-Folded Waveguide Cascaded Traveling Wave Tube Amplifier

The V-band frequency range (50–۷۵ GHz) is a region of the millimeter wave spectrum with great potential application for intersatellite communications and high-performance radar applications, including atmospheric studies, space debris detection, precise tracking, and high resolution imaging [1– ۳]. However, it has to face to the size and power limitation at this frequency range, when using traditional helical traveling wave tube [1, 4] and some novel structure TWTs [5–۷] on such high-frequency band. However, some metal structure TWTs (Coupled Cavity (CC) TWT [8], FWG TWT [9, 10], and so on) can obtain high power but low gains in single tube for strong backward wave oscillation (BWO) instability, also for some FWG cascaded TWTs [11, 12] and CC-FWG cascaded TWTs [13]. In order to obtain a high power and high-gain V-band traveling wave tube in feasible manufacture way, we designed a novel H-FWG cascaded traveling wave tube amplifier. In this design, we use helical traveling wave tube as a first stage amplifier, which is famous for its wide bandwidth and high gain and then exported the amplified signal into the FWG traveling wave tube to get high power. The FWG traveling wave tube has large power capability for its full metal structure and is chosen to get high power in the V-band frequency range. A digitized beam-wave interaction theory model [14, 15] is used to analyze the performance of the designed helix-FWG cascaded traveling wave tube, which has been developed and included in MTSS [16]. In this model the digitized fields, getting the data from electromagnetic (EM) simulation software for arbitrary SWSs, are used to interact with the beam keeping the energy translation and conservation between the beam and the EM wave. Due to its general way to deal with the beam-wave interaction process, this digitized theory model can be used to simulate and analyze the nonlinear performance of traveling wave tube with different SWS. A helix-FWG cascaded traveling wave tube testified the design method and is optimized. Finally, the simulation of the saturated output power is above 34 W with the saturated gain above 33 dB in 5 GHz bandwidth in the first stage helical TWT. And, for the cascaded FWG traveling wave tube in same bandwidth, the saturated gain is above 18 dB achieving the output power to be 800 W. After matching the inputoutput power in the connection, the total cascaded tube achieves 60 dB gain and 800 W in 5 GHz band. The illustration of the helix-FWG cascaded TWT model is presented in Figure 1. The rest of the paper is organized as follows. Section 2 presents the sketch of the digitized nonlinear beam-wave interaction theory model, and Section 3 introduces the principle of the TWT design. Based on the design principle and the digitized theory model, the design and analysis of the H-FWG cascaded TWT are detailed in Section 4. A conclusion is followed at the end of the paper.