Research On Microwave Carrier Suppression Technology

Carrier suppression can cancel in radar,radio frequency identification system leakage transmitter to the receiver carrier power so as to improve the receiver sensitivity,also can improve the sensitivity of the phase lock loop feedback to reduce the phase noise of signal source,can also reduce the useless when signal amplitude modulation power proportion to improve the efficiency of transmission,Therefore,this technology is of great significance in the design of Internet of Things,wireless communication and radar system.In this thesis,based on the principle of vector superposition,the basic framework of carrier suppression system was built,and related components were designed and made by using ADS,HFSS and other software.The hardware circuit of carrier suppression with high suppression degree was constructed by using microwave components with high performance indicators.On this basis,a digital control circuit is designed to realize the automatic control of large carrier suppression and the adaptive adjustment of cancellation circuit when the external environment changes.The specific research includes the following aspects:1.Introduced the research background and basic principle of carrier suppression technology,built the basic model of the system according to relevant theories,designed the basic structure of the circuit and analyzed the indicators of each component.2.Analyze the carrier suppression circuit,and then use ADS and HFSS simulation software to design a coupler with high isolation degree,an electric phase shifter with a high phase shift range,and an electric attenuator with a high attenuation range.After testing each component,connect and test each component,and the carrier suppression degree can reach 80 dBc.The carrier cancellation of hardware circuit is realized.3.Analyze the carrier suppression control system,select the required high dynamic range geophone and high precision ADC and DAC chips,design the hardware and software of the relevant control system,and realize the automatic control function of the system and the adaptive adjustment when the external environment changes.The measurement results show that the carrier suppression system designed in this paper can suppress the 10 GHz 5 dBm single-frequency signal to below-90 dBm,and the carrier suppression degree is stable more than 95 dBc.