| With the development of modern military and scientific research, higher power, higher frequency and higher energy of microwave source has become increasingly urgent. As a new type of electric vacuum device, gyro-traveling wave tubes have filled the blank of millimeter and sub-millimeter wavelengths high-power devices. Because of its characteristics of high peak power, high average power, high gain and high efficiency, it can’t be matched by other devices in the aspect of microwave communication, electronic countermeasure and millimeter wave radar system. Therefore, it is receiving widespread attention.In the process of testing microwave devices, mode conversion can make the microwave source of energy transmit and transfer effectively. Therefore, it has very important research value and application value. Based on the importance of mode conversion, through designing a Q band mode converter whose mode transfer from TE10 rectangular waveguide to TE01 circular waveguide which is used for cold test, this paper makes a deep theoretical simulation, summarizing the design method of the mode converter, and applied to the scientific research. In addition, this paper carried out a large amount of experimental work. Taking the output window and the input coupler as examples, it gives the classification and summary of the de-embedding technology of microwave measurement. The main works of this paper are as follows:1. An overview of the development and application of high power microwave technology and the proposal and classification of gyro have been given. The important roles of gyro devices(output window and input couplers) were briefly reviewed. The research status and research methods of low power mode converter with cold test and de-embedding technologies have been reviewed.2. The design principles and design rules of the converter are studied.3. From the angle of calibration theory in microwave measurement, the de-embedding technology of microwave devices is analyzed. The appearance of VNA system error and its calibration steps have been given in detail, different de-embedding technologies have been analyzed, and the necessity and importance to de-embed on mode converter are also given.4. The mode converter has been simulated and optimized segment, and the influence of tiny changes of the key geometrical size of the mode converter on conversion efficiency was analyzed. From the angle of the equivalent circuit, resonance problem has been analyzed and some effective solutions have been put forward. Through comparison of simulation of different software, a Q band cross mode converter with ultra wide bandwidth and high conversion efficiency is got.5. A brief notice on VNA operation is given, and the test principle and test results of gyro device in cold test to de-embed are emphasized. Through the examples of input coupler and output window, the de-embedding technology has been tested and verified. Using port extension, time-domain function and time door way to de-embed, through the comparison of the results which are before and after de-embedding, and comparing the de-embedding and simulation results, it can be seen that the de-embedding result can significantly improve the accuracy of the test. |
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