Practical Circuit-Based Design Approach for Waveguide Lowpass Filter With Extremely Steep Skirt Response

This paper presents a practical circuit-based design approach for a waveguide lowpass filter with a steep skirt response. For efficient filter design, the proposed structure employs a cascade of troughs with the same physical dimensions. Having identical troughs in most parts of a filter structure greatly alleviates the design difficulty. In addition, our filter design approach is largely based on circuit analysis rather than electromagnetic simulations, greatly expediting filter designs. A WR-75 waveguide lowpass filter example has been designed, fabricated, and measured for demonstration.