Physical parameters of the proposed TBSF layout.

This work presents the development of a bandstop filter with a tunable response. Varactor diodes are used as control elements. Studies and investigations demonstrate the influence of the variable capacitance on the input admittance and on the S-parameters frequency responses of the proposed square-ring resonator geometry. The design of the square-ring resonator is based on mathematical modeling of ideal transmission lines, considering parameters of characteristic admittance and electrical length for odd and even excitation modes. Based on S-parameters in ports, an equivalent circuit model of the resonator geometry is presented. The corresponding results are compared with numerical simulations. Comparative analyses are presented in order to guide the process of optimizing the physical dimensions of the layout. A prototype with dimension 0.0272 was designed, fabricated, and tested. As a measured result, a filter with two rejection bands was obtained, the first at 0.6–1.15 GHz and the second at 1.71–2.28 GHz, with 63.0 and 29.0% tuning range, respectively. In comparison with bandstop filters from the literature, the proposed reconfigurable filter presents a larger tuning range for the first band, sufficient inband rejection levels for several applications, and reduced physical dimensions. The proposed configuration is an attractive reconfigurable filtering device for use in modern communication systems operating below 3.0 GHz.

本研究提出了一款具备可调谐响应的带阻滤波器（bandstop filter）的研制过程，其中采用变容二极管作为控制元件。研究与分析表明，可变电容对所提出的方环谐振器（square-ring resonator）结构的输入导纳以及S参数（S-parameters）频响特性存在显著影响。该方环谐振器的设计基于理想传输线的数学建模，同时考虑了奇、偶激励模下的特性导纳与电长度参数。基于端口处的S参数，本研究建立了该谐振器结构的等效电路模型（equivalent circuit model），并将所得结果与数值仿真（numerical simulations）结果进行对比。为指导该版图（layout）物理尺寸的优化流程，本文开展了对比分析工作。一款尺寸为0.0272的原型样机完成了设计、制作与测试。实测结果显示，该滤波器获得了两个阻带：第一个阻带范围为0.6–1.15 GHz，第二个为1.71–2.28 GHz，二者对应的调谐范围分别为63.0%与29.0%。与现有文献报道的带阻滤波器相比，本文提出的可重构滤波器（reconfigurable filter）在首个阻带上具备更宽的调谐范围，可满足多种应用场景下的带内抑制需求，且物理尺寸更为紧凑。该设计结构是一款极具应用潜力的可重构滤波器件，适用于工作频率低于3.0 GHz的现代通信系统（modern communication systems）。