This thesis focuses on new techniques in synthesis, design, and fabrication for microwave diplexers and multiplexers. Coupling matrix theories are employed with design knowledge to guide computational intelligent techniques to realize complex microwave multiplexers. To achieve compact size and lightweight multiplexers, novel design concepts and emerging fabrication technologies are proposed and implemented. The main contributions of the thesis are:
1) A general all-resonator diplexer/multiplexer coupling matrix synthesis method (GACMS) is presented. Classic filter design knowledge and advanced optimisation techniques are combined to generate high-quality coupling matrices for diplexers/multiplexers with complex topologies.
2) A novel electromagnetic (EM) optimisation method is presented for diplexers. A systematic physical dimensioning method is proposed for a high-quality initial design. A key performance-based objective function is proposed. Together with a powerful optimizer, the diplexer optimisation can achieve a high success rate in a fully automatic process.
3) A resonant manifold multiplexer is proposed based on an all-resonator structure. Different from the traditional transmission line-based manifold-junction, coupled-resonators constitute the manifold-junction. Tailored methods are proposed to synthesis and optimize the multiplexers. The new multiplexer structure offers a more compact footprint.
4) A D-band diplexer is designed based on all-resonator structure. Two commercial fabrication techniques, high-resolution micro laser sintering 3D printing and high precision CNC milling, are employed to the same diplexer design, respectively. Comprehensive measurements and comparisons are conducted for the fabricated diplexers.