Research On Miniaturized Microstrip Filter Of Spoof Surface Plasmon Polaritons

Spoof surface plasmon polaritons is a kind of surface wave existing on the surface between medium and metal.Due to its special dispersion characteristics,ability to break through the diffraction limit and strong field-limiting ability,it has been intensively studied,and is widely used in microwave devices such as antennas,filters,frequency selectors,mixers and power dividers to achieve the device's miniaturization.However,the gradual transition structure in the SSPPs structure leads to the large transverse size of the model,which affects the process of device miniaturization and greatly limits the engineering application of SSPPs devices.In this paper,the SSPPs filter is taken as an example to study the structure of SSPPs,and the specific work is as follows:(1)First of all,a novel transition structure is designed,which is composed of an anti-clockwise "eight" shape structure and two right triangle patches.Then,the transition structure is applied to the general SSPPs model and adjusted and optimized appropriately.Finally,a miniaturized wide-band low-pass filter with a working bandwidth of 13 GHz and the size of 47.52 × 7.47mm2 is designed.(2)A certain number of interdigital-capacitor loop resonators are loaded on the miniaturized wide-band low-pass filter in(1)to achieve the effect of notch in a specific frequency band.The influence of the number,length and branch length of resonators on the filter is studied.A miniaturized SSPPs notch filter with a notch center frequency of 6.9 GHz and a band width of 400 MHz is designed.(3)A composite grating composed of a short grating and a long grating is designed.The filter composed of the composite grating can transform the quasi TEM wave in the microstrip line into the TM wave in the SSPPs without the transition structure,so that the transverse size of the filter reduces two transition structures compared with the original structure.A low-pass filter with the working bandwidth of 7.5 GHz and the size of 33.5 × 7.4mm2 is designed.In this paper,the miniaturization of the SSPPs filter is studied by two ways:designing a novel transition structure and designing a model of no loading transition structure.Three miniaturized filters are designed to verify the effectiveness of the design method,which provides a reference for the miniaturization of SSPPs devices in microwave integrated circuits.