The Research And Design Of RF Microstrip Filter

In recent years,wireless communication technology has been widely and deeply applied and developed in all walks of life.As an indispensable device in a wireless communication system,the performance of the filter will directly affect the entire wireless communication system.As the spectrum resources become increasingly strained,the requirements for filter frequency selection characteristics become higher and higher.Therefore,researching highperformance and low-loss microwave filters is of key significance to improving the performance of wireless communication systems.This paper focuses on the research and design of the high performance and miniaturization direction of the filter.To achieve this goal,this paper first describes the importance of filter design in wireless communication systems,and introduces the current research status of filters at home and abroad,and then the basic theory and design method of the filter are analyzed in detail.Finally,based on this,we completed the design and test verification of the following four filters:(1)Based on the defected microstrip structure,a 0~4.05 GHz wide-stopband low-pass filter is designed.By cascading S-shaped defected microstrip structure with H-shaped defected microstrip structure for the purpose of increasing the stopband bandwidth of the low-pass filter and reducing the insertion loss of the filter.The designed filter is simulated by ADS software,and the designed filter is manufactured and tested.The test result shows that the passband of the designed filter is 0~4.05 GHz,the passband insertion loss is less than 1dB,return loss is less than-10 dB,and stopband rejection below-20 dB,the bandwidth is 6.5GHz.The test results are basically consistent with the simulation results.(2)Based on stepped impedance resonator,a 2.4/5.2GHz dual-frequency microstrip filter that works on WLAN system is designed.The position of the second passband of the filter is adjusted by adjusting the impedance ratio of the stepped impedance resonator.The designed filter is simulated by ADS software,the simulation results show that the first passband insertion loss of the filter is less than 0.3dB and the return loss is less than-25 dB.The second passband insertion loss is less than 0.8dB and the return loss is less than-20 dB.The designed filter basically satisfies the requirements of the WLAN system.(3)Based on the hairpin resonator,a bandpass filter with a center frequency of 2.1GHz is designed.The three-dimensional electromagnetic simulation software HFSS is used to simulate and verify the designed filter.The simulation results show that the designed filter has a passband of 1.9~2.3GHz.The passband insertion loss of the filter is less than 1.5dB,the passband return loss is less than-15 dB,and the relative bandwidth is 19%.(4)Based on the defected microstrip structure,an ultra-wideband microstrip bandpass filter is designed.The ultra-wideband filter was constructed by the short-circuit stub and the low-pass filter designed by the defected microstrip structure.The designed filter is simulated by ADS software and the designed filter is manufactured and tested.The test results show that the designed filter has a passband of 2.9~10.6GHz,a relative bandwidth of 116%,and a passband insertion loss is less than 1dB.The return loss is less than-10 dB,and the 20 dB high-frequency stopband bandwidth is 7GHz.The test results are basically consistent with the simulation results.