Research On Microstrip Filters Based On Parallel Coupled Lines And Spoof Surface Plasmon Polaritons

With the rapid development of wireless communication technology,integrated and high-performance RF transceiver systems have been paid more and more attention.As the basic component of the system,the performance of the filter will affect the working quality of the whole system to a great extent.The miniaturization and high-performance filters have been the focus of the researchers.In recent years,with the emerging of new concepts and the needs of practical engineering,a series of filters with superior performance(wide-stopband filter,absorbable filter,spoof-surface-plasmon-polarized filter)come into being,triggering a new round of hot topics.Based on the above situation,we have done a series of works,as follow:(1)Two high-performance microstrip bandpass filters are designed and analyzed by odd-and even-mode method.Multiple in-band transmission poles and out-of-band transmission zeros ensure the good performance of the filters.(2)A kind of compact wide-stopband filter is introduced,which is composed of a fifth-order coupled line(total electric length λ/4)and two shorted stubs.The fifth-order coupled line can effectively suppress the harmonics up to 7fo or even up to 9f0,and the shorted stub is able to introduce the transmission zeros to improve the frequency selectivity of the passband.(3)A series of simple absorptive filters(|S11|<10 dB@0～2f0)are designed.Based on the complementary-duplexer architecture,the single-port(dual-port)absorptive bandpass(bandstop)filter is obtained by combining the coupled line and T-shaped microstrip structure.Additionally,the design steps are summarized to facilitate the rapid design of the required bandwidth of the absorptive filters.(4)The research on spoof surface plasmon polaritons has been carried out in depth.Firstly,two compact spoof-surface-plasmon-polariton transmission lines have been designed,which occupy a smaller transverse space and achieves a low pass band with good performance.Secondly,a bandpass filter with notched band is designed by using the high-order mode of spoof surface plasmon polaritons.