采用复合左右手结构的微型基片集成波导滤波器设计

为了降低滤波器尺寸以适应sub-6 GHz小型化便携式通信设备的要求，提出一种新型锯齿形的叉指电容复合左右手结构，从而提升传统矩形叉指复合左右手结构的耦合电容。相比于传统结构，该新型结构增大了叉指电容值，降低了谐振频率，减小了滤波器的尺寸，可为sub-6 GHz无线通信系统提供工作频段仅为3.3~3.5 GHz的微型滤波器。为了进一步验证新型滤波器的设计理论和性能，设计、加工一款基于该结构的微型化基片集成波导(SIW)滤波器。测试结果表明：改进型结构滤波器的中心频率为3.35 GHz，工作带宽为200 MHz，插入损耗为2.4 dB，滤波器尺寸仅为10.0 mm×7.4 mm；相较于传统复合左右手结构滤波器（中心频率为6.8 GHz），该滤波器的中心频率降低了50%。新型锯齿形叉指复合左右手结构能有效降低射频滤波器的工作频率，减小滤波器尺寸，适用于工作在6 GHz以下频段的微型滤波器设计。

Design of compact substrate integrated waveguide filter based on composite right/left-handed structure

A novel composite right/left-handed (CRLH) structure with zigzag interdigital capacitor structure was proposed to improve the coupling capacity of conventional rectangular CRLH structure, in order to minimize the filter size to meet the requirement of sub-6 GHz compact portable communication devices. Compared with the conventional CRLH structure, the proposed zigzag interdigital CRLH structure can increase the capacitance of interdigital capacitor, reduce the resonant frequency and miniaturize the filter size, which makes it possible for sub-6 GHz wireless communication system to have a compact filter with working frequency band of 3.3 to 3.5 GHz. A SIW filter based on zigzag interdigital CRLH structure was fabricated and tested, to further demonstrate the designed theory and performance of the structure. Results show that the proposed filter works at the center frequency of 3.35 GHz with bandwidth of 200 MHz; and the insertion loss is 2.4 dB, and the filter size is only 10.0 mm × 7.4 mm. The proposed filter reduced center frequency by 50%, compared with the filter using the traditional CRLH structure (the center frequency is 6.8 GHz). The novel zigzag interdigital CRLH structure can effectively reduce the resonant frequency and the filter size, which is suitable for the design of compact filters for sub-6 GHz wireless communication system.