Twt Helix Cold Parameters Automatic Test System

Helix traveling wave tube (TWT) is a significant microwave electronic device. Because of the advantages that wide bandwidth, high gain, wide dynamic range and low noise, it is widely used in the field of modern electronic warfare, radar, communications and weak signal reception. The low-noise and small power TWT is a widespread and important TWT which generally adopts the helical slow wave structure. Dispersion and interaction impedance are two strongly major cold parameters of helical slow-wave structure. Dispersion characteristics determine the operating voltage and frequency bandwidth of TWT, and interaction impedance determines the gain and efficiency of TWT. The measurement of two parameters occupies an important position whether in the design stage of tube or in the quality testing stage. Therefore, it is very important that developing a practical and convenient automatic measurement system for improving development level and mass process of TWT.Firstly, the paper has a further study of the development of the cold parameter measurement of TWT’helix at home and abroad and analyzes measurement principle of dispersion and interaction impedance. At the same time, the advantages and drawbacks of different test methods are compared. According to the requirements of the system and characteristics of automated testing, the measurement method of the system is determined under the existing experimental conditions.Secondly, the hardware test platform is designed and set up, which consists of helix movement subsystem, mechanical fixture subsystem, data acquisition subsystem and central control subsystem. The author plans the platform’ structure and designs the system’ fixation and fixture. In addition, probe and its mobile platform are made and the design of the hardware interfaces between the various subsystems is completed.Furthermore, the test software of the system is developed in the VC environment, which can achieve the automatic control for electronically controlled translation stage and communication with the PNA by the GPIB interface. Then, the sample’ automatic test and data processing can be completed. The software has a lot of advantages, such as beautiful interface, perfect test functions. The results are displayed and stored in the form of graphical and table form. The automatic test system is built up on the basis of hardware platform and software. It can measure the cold parameters of helix TWT at frequency from6GHz to18GHz.At last, two uniform samples are measured using the system and the measured results are compared with calculation results of dedicated CAD software. In addition, the test error has been analyzed. The experimental results show that the measured data and the calculation data of the simulation software match well, and the repeatability and consistency of the measured results are good. The system can work stable.