Research on High Precision Modeling and Design Method of Microstrip Adjustable Filter

ABSTRACT This paper introduces a highly accurate equivalent circuit extraction method for microstrip filters, capable of producing precise equivalent circuit models with a normalized mean square error (NMSE) of less than 0.003. The extracted equivalent circuit models are well‐suited for circuit simulations and serve as a powerful tool for the simplified design of tunable filters. To demonstrate the effectiveness of the method, a fourth‐order tunable filter with fixed bandwidth and adjustable center frequency, as well as a fifth‐order tunable filter with adjustable center frequency and bandwidth, was designed and implemented. The results from circuit simulations, electromagnetic field simulations, and experimental measurements exhibit strong consistency, confirming the reliability and practicality of the proposed method.