Study Of The Filters Based On Complementary Split Ring Resonators (CSRR)

Filter is of great importance to the wireless communication circuits. It is widely used in the mirror frequency suppression, noise reduction, FDM and mixer, amplifier, oscillator. Smaller and better filters are eagerly required with development of the communication system, and many kinds of filters are studied to satisfy small and light microwave system.The analyzing and designing of a novel kind of filter based on the complementary split ring resonators (CSRR) are presented in this dissertation. First of all is that the equivalent circuit of both the split ring resonators(SRR) and microstrip loaded with SRR are investigated as the complementary parts of SRR. Secondly, the equivalent circuits of the CSRR are studied and the microstrip loaded with CSRR and microstrip with gap loaded with CSRR are simulated. It is found that the important parameters (the out radius, the gap between the inner ring and the outer ring, the width of the gap) have great impact on the resonate frequency. Based on the coupling between the strip and the CSRR, the configuration of the low pass filter and the high pass filter are designed, and both of the low pass filter and the high pass filter have better performance. The band pass filter with good results can be obtained by combining the low pass filter with the high pass filter. Through numerical simulation, proper parameters are chosen. The pass-band of the band pass filter is from 1.6 GHz to 2.9 GHz, the out-band suppression is nearly -60dB, and the rectangle coefficient is almost 2. It is also found that bandwidth of the band pass filter is controllable by adapting the radius of the CSRR. Finally, the filters with CSRR etched on the ground are made. The band pass filter has a bandwidth of 1.5 GHz to 3.15 GHz with the rectangle coefficient of near 2, the group delay is less than 10ns. It shows that the measured data is agreeable with the simulated data.