A Novel Unbalanced‐to‐Balanced Switchable Quadruplexer With High Off‐State Suppression

In this paper, a novel unbalanced‐to‐balanced switchable quadruplexer with high off‐state suppression is proposed. Four channels are realized through four pairs of step impedance resonators and uniform impedance resonators with different center frequencies in the quadruplexer. Furthermore, the flexible and controllable channel switching function is achieved through loading PIN diodes and their bias circuits at the open‐circuited ends of the resonators. To verify the feasibility of the proposed design, a quadruplexer with center frequencies of 1.227, 1.575, 1.9, and 2.3 GHz, respectively, is designed and fabricated. Measurement results indicate that the proposed quadruplexer achieves four independently controllable channels with an off‐state suppression of up to 51 dB. It is expected to be applicable to combined applications of global navigation satellite systems and mobile communication systems.