一种S波段小型宽带微带带通滤波器优化设计

基于并联短截线谐振器与联接线变换器构成的传统微带带通滤波结构,提出了一种工作在S波段的改进型宽带带通滤波器。以三阶结构为例,通过将两侧并联短截线进行弯折,形成耦合线结构;将中间并联短截线进行拆分,变为并联的短路线和开路线,实现了在通带性能基本不变的前提下,获得阻带可调控的传输零点,进而提高过渡带陡峭度。为了进一步抑制阻带,在滤波器两侧级联扇形微带低通滤波结构,改善阻带性能。利用ADS和HFSS仿真软件对滤波器结构进行仿真优化设计,并最终进行了实物加工和测试。实测结果表明,通带内2~4 GHz插入损耗小于0.7 dB,回波损耗大于17 dB,通带外4.6~6.5 GHz 阻带抑制达到20 dB 以上。

Optimized Design of an S-Band Compact and Broadband Microstrip Bandpass Filter

Based on the traditional microstrip bandpass filter structure which is composed of shunt stub resonators and admittance inverters, an improved wideband bandpass filter which operates in S-band is proposed. Taking the third-order structure as an example, the shunt stub on both sides is bent to form the coupling line structure and the intermediate shunt stub is divided into parallel short-circuited stub and open-circuited stub. By doing so, the stopband adjustable transmission zero is obtained, and then the steepness of the transition zone is improved under the condition that the passband performance remains unchanged. In order to further suppress the stopband, the sector microstrip low-pass filter structure is cascaded on both sides of the filter to improve the stopband performance. The design of the filter structure has been optimized by using ADS and HFSS, and finally the physical processing and testing have been carried out. The measured results show that the insertion loss of 2-4 GHz in the passband is less than 0.7 dB, the return loss is greater than 17 dB, and the stopband suppression of 4.6-6.5 GHz outside the passband is more than 20 dB.