Slow-wave Structure Of The Line Cold Measurement System Study

Traveling wave tubes (TWT) are broadband, high efficiency, high power microwave amplifiers, which are widely used in many electronic equipments, such as radars, communications, television, radio and electronic warfare.Two cold-test parameters determine the working voltage, frequency band, efficiency and gain of TWT. They are dispersion and interaction impedance of the slow-wave structures (SWS) in TWT, which are very important targets for TWT. At the time of design, the measurement of dispersion and interaction impedance will be used as design verification and improvement. At the time of manufacture, the measurement will find the problems of the slow-wave structures in machining, weld and fitting.In the domestic factories of TWT manufacture, the data of dispersion and interaction impedance are usually obtained by simulation. Although the measurement of beam-wave interaction can get the data, which including large and expensive equipments. But it can not find the blemish of SWS as early because it must wait until the finishing of whole manufacture. Because of the disadvantages such as low automatism, timeworn, the foreign measurement equipments can not meet the demands of measurement on-line.The aim of this dissertation is to develop a measure system of dispersion and interaction impedance, which has high measure precision and automatism. In this dissertation, different theories of measurement are discussed. Through the comparison, we use traveling-wave method to measure dispersion and nonresonant perturbation method to measure interaction impedance.The measure system is based on virtual instrument technology. Its hardware includes measurement flat, servo motor, vector network analyzer (VNA) etc. And its software is programmed by LabView. The measurement system can automatically control the movement of servo motor and communicate with VNA through GPIB bus to setup the measurement variable automatically, measure the phase of S parameter. It also can progress the measurement data on the background, display the results by graph data, store them in the data files.The system has practically measured three SWS samples. Through the comparison with the results simulated by HFSS and CST Microwave Studio, validate its good measure repetition, measure consistency and high precision.The measure system has already gotten authorization from the relative factory. Its practical usage will accelerate the design and manufacture of TWT.