基于人工表面等离激元的小型化电可调缺口带滤波器

Miniaturized electronically controlled notched band filter based on spoof surface plasmon polaritons

具有小型化的缺口带滤波器在微波集成系统中具有广泛的应用前景.本文基于倒山形单元的人工表面等离激元(spoof surface plasmon polariton,SSPP)提出了一种新型小型化电可调缺口带滤波器.与相同横向尺寸的传统SSPP单元相比,所提出的倒山形单元的色散曲线表现出更好的慢波特性,渐近频率降低至原来的55%.缺口带的频率可通过调整变容二极管两端的偏置电压来动态控制.随着偏置电压从0.5 V增至30 V,缺口带频率从2.1 GHz移动到2.3 GHz,实现动态调节.仿真结果表明,缺口带滤波器通带内实现了较低的插入损耗(S_(21)<-1 dB)和良好的回波损耗(S_(11)>-10 dB),并且具有小型化的优势,尺寸仅为0.78λ_(g)×0.35λ_(g),λ_(g)是中心频率处的波长.采用印刷电路板技术实际加工了缺口带滤波器.实物测量和仿真结果吻合较好,验证了设计的可靠性.

In this paper,a novel miniaturized electronical controlled notch band filter based on spoof surface plasmon polaritons(SSPPs)with inverted“山”-shaped unit is designed and experimentally demonstrated.The notch band filter is mainly composed of four parts:microstrip transmission line,transition structure,inverted“山”-shaped SSPPs,and split ring resonator(SRR)structure,and a varactor diode is embedded in the slit notch of the SRR structure to realize electronic control.Comparing with the traditional SSPP unit with the same lateral size,the dispersion curve of the proposed inverted“山”-shaped unit shows better slow wave characteristics,and the asymptotic frequency is reduced to 55%.The frequency of the notch band can be dynamically controlled by adjusting the external bias voltage at both ends of the varactor diode.As the external bias voltage increases from 0.5 V to 30 V,the notch band frequency can be changed from 2.1 GHz to 2.3 GHz and achieve easily electronic regulation.The simulation results show that the notched band filter achieves low insertion loss(S_(21)<–1 dB)and great return loss(S_(11)>–10 dB)in the pass band,which has the advantage of miniaturization with the size only 0.78λ_(g)×0.35λ_(g).It is worth noting that when the equivalent capacitance of the slit notch is changed,the transmission coefficient of the notched band is always less than–15 dB,showing superior bandstop performance.At the same time,by comparing and analyzing the electric field distribution of notch band filter,the transmission mechanism of microwave signal is further verified.In order to verify the its effectiveness,the traditional printed circuit board technology is used to fabricate notch band filter.The measurement results are in good agreement with the simulation ones,verifying the feasibility of the design.The electronically controlled notch band filter has higher integration and can effectively suppress the interference frequency band.