Design Method of Frequency-Reconfigurable Filtering Couplers

A design method of frequency-reconfigurable filtering coupler is proposed. Two kinds of reconfigurable filtering transmission lines (RFTLs) with 90° or -90°phase shift are designed. By substituting the conventional λ/4 transmission lines with the proposed RFTLs, the reconfigurable filtering rat-race coupler and quadrature coupler are achieved.