A Broadband Microwave Power Monitoring Component Development

With the rapid development of science and technology, microwave signal is used more widely than before, the most important parameter of microwave signal is power. The measurement and control of microwave signal has become the most important part of microwave technology, and microwave power meter will be smaller, lower cost, wider band, and higher precision. So it is very important to construct a broadband microwave power detecting system.The objective of this dissertation is to design and manufacture8GHz-18GHz microwave power detecting system. The detecting power range is-5dBm～45dBm, and the uncertainty is less than±0.5dB. The system scheme is:a high power signal is coupled to a weak signal through broadband directional coupler, and then the weak signal is converted into a low-frequency voltage signal. At last, the voltage signal is collected and displayed. The component includes broadband double ridge waveguide directional coupler, double ridge waveguide-coaxial-microstrip line conversion circuit, microwave detector, broadband power equalizer and power indicated circuit.One of the important researches in this dissertation is the implementation of broadband high power directional coupler. The theory of directional coupler and characteristics of double ridge waveguide are analyzed. Criteria double ridge waveguide WRD6.50and cross rectangular coupling hole are used to design the directional coupler. After simulated in HFSS software, a directional coupler is successfully designed. The test results as follows:in8GHz～18GHz, the coupling coefficient is40.4±0.7dB, and the directivity is greater than15dB.In order to achieve high-performance conversion between different transmission lines, double ridge waveguide-coaxial conversion circuit is also researched specially. Based on quarter-wavelength impedance transformation method, an improved conversion circuit is designed. Insertion loss of the circuit is less than0.67dB, the input reflection coefficient is lower than-14.5dB.According to the system design requirements, an8GHz-18GHz microwave deector circuit is designed with logarithmic detector chip HMC662LP3E and external lunped elements. After analysis of detector test results, a well-matched microstrip boadband equalizer is designed by using different resistor-loaded open branch resonators. The equalized value of the power equalizer is about9.025±0.2dB and the input and output reflection coefficients are all lower than-14.2dB.At last, all microwave unit-circuits are connected and power indicated circuits are manufactured. And then the overall power detecting components are debugged and tested. Compared with criteria power meter, the test accuracy of the system is±0.5dB in-5dBm～45dBm power range. Overall, the specifications tested above approximately meet the project requirements.