Design Of MEMS Reconfigurable Bandpass Filter

With the rapid increment in the demand of multi-functional compact devices,the design of reconfigurable filter has attracted more and more attention,however,there are still strict restrictions on the size and performance in the course of designing.The highperformance reconfigurable filter is the core component of the multi-band communication system,and there will be a broader application market in the future.Firstly,the third chapter of this paper starts from the theory of stepped-impedance resonators,improves the designing,folds the relatively long grounded high impedance lines,and uses PIN diodes to realize discrete reconfigurable filters by switching low impedance line lengths.The bandwidth in the passband of three reconfigurable filters based on this design is greater than 150 MHz,and the band outside the center frequency greater than 450 MHz is greater than 40 dB.This design makes the structure of PIN diode reconfigurable filter more compact,and also facilitates the design of the bias circuit portion.Secondly,the reconfigurable filter in the fourth chapter uses a varactor diode as a tuning element.Combined with related resonator theory,the course is verified by simulation and test.Among them,the central branch load variable-capacitance diode tuned filter has a continuous tuning frequency in the range of 1.85GHz~ 2.55 GHz,and the change of insertion loss is between 2.8 dB and 6.5 dB,also the band outside suppression is greater than 35 dB off the center frequency 500 MHz.There is also a mixed-coupling comb-line tunable filter tuning range: 0.98GHz~1.45 GHz,each bandwidth in the passband is approximately 65 MHz,and the insertion loss ranges from 4.5 dB to 6.5 dB.Finally,the MEMS reconfigurable filter in the fifth chapter uses a Cross-shape step impedance resonator as the basic unit.To realize discrete reconfiguration,the grounded high-impedance line of the resonator is folded,and a PIN diode is used to switch the electrical length at the low-impedance end.A three-channel S-band reconfigurable MEMS filter with a bandwidth of no less than 180 MHz is designed,so it is in the bandwidth of no less than 980 MHz three-channel X-band reconfigurable MEMS filter.At last,it is fabricated in the process MEMS by using silicon tech,and this design is beneficial in switching between analog and digital channels.