Suspended Stripline Low-pass Filter Design for Wide Stopband Attenuation Applications

Abstract

This paper involves the design of asymmetrical generalized Chebyshev low-pass filter realized with a suspended substrate stripline. The study presents the synthesis and design of an asymmetrical prototype with a degree of 11, the cut-off frequency of 2.5 GHz, better than 26 dB as passband return loss and a broad stopband rejection of 55 dB. The filter produces 11 transmission zeros (attenuation poles), one at infinity and 5 pairs located at finite frequencies offering better wide stopband attenuation performance as well as sharp selectivity. The filter is built based on suspended stripline structure (SSS) using aluminium as a cavity and with 2mm as a ground spacing. The filter measurements show a reasonable agreement has been achieved with the simulated response.An eleventh-order lowpass filter satisfying generalized Chebyshev response with asymmetrical topology, a wide stopband rejection and high selectivity has been presented. The filter has a total of 11 TZs, one is located at infinity and 5 pairs located at different finite frequencies contributing response improvements in both passband and stopband re- gions