Particle swarm optimization method for designing innovative diplexer using heterogeneous filters

This paper studies the adoption of particle swarm optimization (PSO) method to develop and optimize a small microstrip diplexer with heterogeneous filters. The diplexer’s topology combines stepped impedance and hairpin resonators with a coupled junction. This structure makes it suitable for 5G and WiFi applications, as it operates at 3.5 and 5 GHz. Consequently, the designed diplexer exhibits considerable advantages of innovation and compactness, having a significant small size of 32 × 18 mm2. Moreover, the simulation and measurement results show good agreement in terms of low insertion loss S21 and S31 of about 1.3 and 1.4 dB respectively, at both bands. In addition, it exhibits good return loss of about 17 and 25 dB as well as this; there is high isolation of more than 35 dB between channels. Finally, the equivalent circuit of this diplexer was analyzed and simulated to validate the behavior of the proposed diplexer design.