Low-pass filter of suspended stripline design with finite transmission zeros for stop-band rejection improvement

In this article, we present the design of the suspended stripline low-pass filter (LPF) with finite frequency transmission zeros for enhancing band-edge roll-off and increasing stop-band signal rejection levels. The proposed LPF is a seventh-order circuit which exhibits two transmission zeros in the stop-band region. The LPF has achieved the benefits of size compactness, low dispersion, high immunity to the noise inference, and low insertion losses. An equivalent circuit model composed of lumped elements is developed to predict filter's characteristics, and ultimately it is used to calculate the LPF's frequency responses during the design. The equivalent circuit model is used to accelerate the proposed LPF design in the early stage with its calculated data validated by a commercial electromagnetic software simulation. Experiment is conducted to verify the LPF's design and its performance.