Wide Stopband Microstrip Triplexer Using Common Crossed Resonator and Uniform Impedance Resonator

A novel microstrip triplexer with a common crossed resonator and some uniform impedance resonators (UIR) is proposed in this paper. The crossed resonator is theoretically analyzed and proved to be able to resonate at three different frequencies. By using the crossed resonator as the common resonator, a compact structure can be gained as no extra matching network is needed, and the number of the resonator can be reduced effectively. Moreover, a wide stopband is obtained by setting the crossed resonator and UIRs working at the same fundamental frequencies but different higher order resonant frequencies. To demonstrate the design procedure, a triplexer with a third order Chebyshev response in each channel is fabricated and measured. The measured result is in good agreement with the simulated one, showing an attenuation of 20 dB up to 8 times the first channel frequency.