Microstrip switchable filtering balun with three operating modes

A microstrip switchable filtering balun with three operating state is presented in this paper. Three operating modes are dual-band filtering balun operating at 1.43 GHz and 1.76 GHz, low-band filtering balun centering at 1.43 GHz for WMTS application, and high-band filtering balun working at 1.76 GHz for wireless communication. Three operating modes can be independently switched by controlling the voltages of PIN diodes loading at the open-ended of dual-mode resonator. The dual-band bandpass filtering responses are achieved by embedding two pairs of dual-mode resonators. The simulated result shows good performance.