Microwave Dual-Band Bandstop Filter with Improved Spurious Resonance Behavior
A design technique to improve the spurious resonance behavior of dual-band bandstop filters is presented. A compact dual-band bandstop filter with two stop bands that can be controlled independently with improved passband frequency response is designed. The operational bandwidth of the proposed compact dual-band bandstop filter is increased by pushing the first spurious resonance from being about twice the resonance frequency to more than three times the resonance frequency. Stepped impedance open loop resonators with substantially increased outer-edge width are used to improve the spurious resonance response. Both simulation and measured results are presented and good agreement is obtained between the results. The fabricated filter exhibits dual operating frequencies at 1460 MHz and 2640 MHz with 5.5% and 5% stopband fractional bandwidths, respectively. (c) 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE 23: 627-633, 2013.
bandstop filters dual-band filters microstrip filters open-loop resonators spurious response