This paper presents a high-performance microstrip diplexer based on the coupled triangular microstrip cells. The proposed diplexer has a compact size of 0.018 kg2. It is designed to work at 1 GHz for aeronautical military systems and aeronautical navigation and 1.3 GHz for active sensors, GNSS repeaters, radiolocation, and satellite systems. The low insertion and return losses better than 0.21 dB and 25 dB respectively, are obtained at both channels. Another advantage of this diplexer is high isolation of 40 dB between its channels. Moreover, the 1st, 2nd and 3rd harmonics are suppressed with a maximum level of - 30 dB. The designing process is based on proposing an LC model of a novel microstrip cell. Then, the effective parameter on the resonance frequency is found. To verify the designing method, the introduced diplexer is simulated, fabricated and measured. The simulation results are in a good agreement with the measurements.
