Synthesis of Wideband Bandpass Filter With Optimized Matrix Scaling for Direct Circuit Implementation Using Lumped Elements

This letter describes a synthesis method for wideband bandpass filters (BPFs) that uses an optimized matrix scaling technique for direct circuit implementation. The method commences with constructing filtering polynomials in the bandpass domain tailored for bandwidth, passband response, and the locations of transmission zeros (TZs). Then, the in-line lumped-element prototype is realized through a simple implementation. Subsequently, the proposed scaling matrix with solvable restraints and a tuning process is employed to adjust practical component values while maintaining the predetermined responses flexibly. The complexity of the circuit can be reduced by selecting critical values of the scaling factors. Finally, the proposed method is validated by several synthesis examples and measured results.