Research And Design Of Multimode Reconfigurable Microstrip Filter

With the rapid advancement of wireless communication technology,the performance and complexity of communication systems are constantly improving.The reconfigurable filter can replace the filter bank in the system and has the advantage of reducing system complexity,which has piqued the interest of researchers both at home and abroad.Two multi-mode reconfigurable microstrip filters are realized using varactor diodes based on related theoretical research.The paper’s research work is summarized as follows:A single-band multimode reconfigurable filter structure based on an open-loop aperture resonator is proposed and designed to meet the multi-mode,multi-modulation,and high integration requirements of modern wireless communication systems.To achieve its band-pass characteristics,the reconfigurable filter employs the structure of a half-wavelength transmission line centrally loaded with a hole resonance unit,and loads varactor diodes at both ends of the open-loop transmission line and the hole resonance unit to control the odd and even modes of the resonator,respectively.By adjusting the bias voltage,the resonant frequency and center frequency can be reconfigured.The results of field and circuit co-simulation and physical testing show that its center frequency can be continuously adjusted in the range of 2.04～2.5GHz,which covers the corresponding frequency bands of FDD,TD-LTE,and ISM.The insertion loss is between 1.9～2.5d B and the return loss is less than 25 d B during the adjustment process.The proposed reconfigurable filter can meet multi-standard communication requirements with a single filter,which aids in communication system integration.To meet the requirements of multi-standard GNSS RF signal receivers,a dual-band multimode reconfigurable filter structure based on parallel dual resonant units is proposed and designed.To achieve the dual-frequency bandpass characteristics,the reconfigurable filter employs two resonant units that share mutual folded π-shaped I/O feed lines,with the upper passband realized by a stub-loaded step impedance resonator and the lower passband realized by a pair of coupled quarter-wave uniform impedance resonators.These two resonant units are fed via folded-shaped feed lines.The two passbands can be reconfigured by using two sets of varactor diodes.Furthermore,the passband selectivity is improved by introducing source-load coupling to increase the transmission zero points and adding a DGS structure to suppress harmonics.The simulated and measured results show that the filter’s two passbands achieve center frequency tuning ranges of 1160～1280 MHz and 1530～1630 MHz,respectively,and that each passband can cover GPS,GLONASS,Galileo,and BDS signals.In all tuning ranges,The insertion loss is better than 2.1 d B and the return loss is better than 26 d B.The proposed dual bandpass filter design demonstrates the flexibility of independent passband control to be compatible with multi-standard signals and adaptable to the deployment of new GNSS standard specifications.The paper has 40 pictures,4 tables,and 102 references.