Microwave resonator filter optimization using particle swarm optimization technique

This article focuses on the design and optimization of a microwave resonator filter aimed at mitigating unwanted interferences and harmonic distortions in mobile communication systems. These disturbances can significantly degrade signal integrity across communication channels. A Particle Swarm Optimization (PSO) technique is employed to optimize this coupling matrix, guided by a novelcost function. This cost function integrates polynomial expressions of the filter’s reflection coefficients (Fs) and transmission zeros (Ps), while also accounting for various sources of error. These include inaccuracies arising from filter geometry, parasitic capacitances introduced within the resonator structure, and deviations related to transmission line length and its relative permittivity. The PSO algorithm identifies the most optimal solution within a defined search space, which is then used to fine-tune the polynomial functions governing the filter’s performance. The optimization process effectively minimizes pass-band ripples and significantly enhances filterselectivity. A prototype filter was developed using a square open-loop resonator and inline waveguide filter operating in the frequencies ranges of 2.25 GHz to 3.19 GHz and 2.4 GHz to 3.50 GHz Simulation and experimental results confirm that the designed filter meets the targeted specifications, demonstrating its effectiveness in improving signal quality within modern communication systems.