Wideband Equalizer with Cascaded Band-stop Filter Design for Radiometer Applications

This article presents a novel design approach for a wideband passive microstrip network, comprising a cascaded bandstop filter and equalizer, to improve the performance of passive radiometer systems. The proposed network enhances the gain flatness, particularly at the input of the low-noise amplifier (LNA) in the radiometer receiver, and optimizes the output spectrum by reducing frequency-dependent distortions. The cascade architecture also contributes to a more uniform spectrum in the operating bandwidth, improving the overall image quality of the radiometer and ensuring more accurate detection of objects in passive imaging applications. Simulations and momentum analysis are performed using Advanced Design System (ADS) software, while the design is fabricated on a ROGERS 4350B substrate. In addition, a sensitivity analysis is performed to minimize the impact of manufacturing tolerances on the final performance, ensuring the reliability and precision of the proposed structure. The results demonstrate a significant improvement in the radiometer output response, with a gain flatness of up to 5-7 dB in the desired frequency range.