A compact quasi-lumped LTCC diplexer for radar application

An integrated quasi-lumped diplexer based on low temperature cofired ceramic (LTCC) technology is presented. The diplexer is made of L-band low pass filter (LPF) formed by lumped element and X-band band pass filter (BPF) adopting step impendence resonator (SIR). The diplexer's performance has been simulated and optimized by EM simulator. An experimental diplexer has been made and measured. The measured result of the frequency response agrees very well with the simulated one, the LPF's insertion loss is less than 1dB, and 1dB cut-off frequency is 1.46GHz; the BPF's insertion loss is less than 3.5dB, and 1dB bandwidth is about 0.6GHz at the center frequency 8.3GHz. Its good performance, small size and relatively simple structure make it a good candidate as an integrated diplexer for various LTCC systems.