Design of Bandpass Filter at 3 GHz for S-Band Radar Application

Bandpass filters play a crucial role in S-band radar systems, commonly used for military surveillance, weather monitoring, and other radar applications. These filters enhance signal clarity by suppressing unwanted frequencies while allowing desired signals to pass through. Designing a high-performance filter within the $2-4 \mathrm{GHz}$ range, specifically at 3 GHz, is challenging due to trade-offs between return loss, insertion loss, and bandwidth. Achieving a design that balances these parameters is critical for optimal radar functionality. This paper presents the design of a 3 GHz bandpass filter using an FR4-epoxy substrate with a 200 MHz bandwidth. A lumped element circuit was developed and later converted into a microstrip layout to facilitate precise fabrication. Electromagnetic simulations were conducted to evaluate the filter’s performance. The filter was designed using the Chebyshev approximation to minimize insertion loss and optimize the sharpness of the roll-off. ADS (Advanced Design System) simulation software was employed to validate the performance, focusing on achieving a return loss of $\mathrm{- 1 0} \mathrm{dB}$ or better across the passband. The design achieved minimal insertion loss and satisfactory return loss across the passband, demonstrating its effectiveness for radar applications. Comparative analysis with existing literature further validates the proposed design’s superior performance.