High rejection planar diplexer on liquid crystal polymer substrates using oversizing techniques

An original planar dual behavior resonator (DBR) diplexer operating at 18 GHz is discussed in this paper. The effort lies in the implementation of oversizing synthesis techniques on a low-cost high-performance liquid crystal polymer (LCP) substrate for accessing to high isolation level between adjacent frequency bands. Artificial high Q factor structures can be reached using oversized resonators, while keeping the same technological parameters reduced overall dimensions. Full wave simulations and measurements of the scattering parameters are presented.