Compact evanescent mode waveguide duplexers

Evanescent mode waveguide duplexer with coaxial posts and irises coupling sections was presented in this article, and the unload Q factor and power carrying capacity were discussed. Such duplexers are suitable for some integrated systems having volume constraints. One design example simulated by Mode Matching Method was also given. Example duplexer with total 14 sections having upper stopband widths of up to five times the fundamental bandpass center frequency was presented. The center frequencies of two passbands were 1.87 GHz and 2.09 GHz, and the corresponding fractional bandwidth were 6.9% and 7.7%. The insertion losses in both passband were 0.8 dB. With the irises coupling structure which was used to shrink the longitudinal dimension especially for narrow bandwidth devices, the volume of this duplexer was 183 × 30 × 17 mm³, it was 1/5 of its conventional duplexer.