Switchable Diplexer Based on Coupling Control

In this brief, a switchable diplexer is presented based on coupling control. It consists of two switchable filter channels that can be reconfigured with four working states. The on- and off-states of each channel are enabled by controlling the coupling between the output feeding line and a resonator in this channel. When one channel is switched off, the resonators in this channel act as non-resonance nodes of the other channel, which can generate transmission zeros to enhance the skirt selectivity of the other channel without using additional circuits. Moreover, the second, third and fourth harmonics of each filter channel are suppressed, resulting in wide stopband responses. The detailed analysis and experimental results are given to verify the proposed ideas.