Coupling matrix sign reversal transformation

This paper explores a new transformation of coupling matrix (CM) called sign reversal technique. It is mathematically proved that, sign reversal transformation holds S-parameter invariant property by preserving eigen values and eigen vectors of original CM. It is also showed that, sign reversal operation offer another type of similarity transformation. Proposed sign reversal technique is independent of filter order and coupling topology. Also, this technique is equally applicable to resonating as well as non-resonating nodes which provide more degree of freedom for design. Two different lossless filter examples are examined to verify this technique. Finally, a 4-order inline bandpass filter is designed and simulated to illustrate sign reversal technique in bandpass frequency domain.