Design of multiple-passband filters using coupling matrix optimisation

• Published in: IET microwaves, antennas & propagation Vol. 6; no. 1; pp. 24 - 30
• Main Authors: SHANG, X, WANG, Y, NICHOLSON, G. L, LANCASTER, M. J
• Format: Journal Article
• Language: English
• Published: Stevenage Institution of Engineering and Technology 01.01.2012; The Institution of Engineering & Technology
• Subjects: Applied sciences; Circuit properties; Convergence; Electric, optical and optoelectronic circuits; Electronic circuits; Electronics; Exact sciences and technology; Frequency filters; Genetic algorithms; Joining; Microwave antennas; Microwave circuits, microwave integrated circuits, microwave transmission lines, submillimeter wave circuits; Optimization; Reflection; Waveguide filters; X-band; Waveguide filters; Return loss; X band; Characteristic polynomial; Iterative method; Centimetric wave; Specification; Microwave filter; Quadratic programming; Transmission zero; Optimization; Multi-band circuit; Difference frequency; Simulation; Genetic algorithm; Sequential method; Band pass filter; Cost function; Matrix method; Capacitive coupling; Localization; Interconnected system
• ISSN: 1751-8725; 1751-8733
• DOI: 10.1049/iet-map.2011.0261

This study presents the design of microwave filters based on the coupling matrix approach; determination of the matrix is based on a hybrid optimisation algorithm which may be applied to cross-coupled filters having diverse topologies. Various filter responses from dual-band to quad-band are given as examples of the approach. The optimisation is performed on the coupling matrix and a genetic algorithm (GA) is employed to generate initial values for the control variables for a subsequent local optimisation. The novel cost function in this study measures the difference of the frequency locations of reflection and transmission zeros between the response produced by the coupling matrix and the ideal response. Convergence of the coupling matrix optimisation is fast, and no initial values for the control parameters are required by the GA. An eighth-order X-band dual-band waveguide filter with all-capacitive-coupling irises has been fabricated and measured to verify the design technique. An excellent agreement between simulation and experimental result has been achieved.