Optimization of Multi-Ports Combline Filter Using Admittance Extraction Technique

Abstract

This research study proposes a new geometric dimensioning and sizing adjustment strategy of a multi-ports combline filter based on rectangular waveguide cavities and Chebyshev approximation using High Frequency Structure Simulator (HFSS) for 1.85GHz microwave bandpass applications. The optimization technique is based on introducing additional internal ports to the filter design by admittance [Y] matrix extraction in a specific way that offers the advantage to directly access each resonator’s central frequency (fc), coupling matrix (CM) coefficients and external quality factor (Qs). Extracted values allow approximating the filter specified data via simple tuning procedures. A new structure of a 4th pole Chebyshev bandpass filter is developed to resonate at 1.82GHz and present good electromagnetic response for the whole frequency band. The developed filter design can be easily adapted to other filter prototypes due to the accurate availability of the applied optimization method that allow designing other new high performance filter topologies.