Multiport Isolated Quadrature Combiners With Filtering Characteristics Based on Multiway Canonical Resonator Lattices

A comprehensive methodology is presented for the systematic design of multiway filtering isolated quadrature couplers based on coupled resonator lattices. The basic design principle for the multiport combiner is first introduced as a mapping between a pair of synchronously tuned coupled resonators and a transmission line (TL) section whose electrical length corresponds to a quarter wavelength at the resonant frequency. Once this mapping is set, it can be seamlessly utilized to design the multiway filtering couplers based on resonator lattices. A number of cross-coupled resonator networks that realize three-, four-, and five-way couplers are then introduced. The proposed topology enables in-line power combiner architectures, which are very useful in the realization of high-power systems. Moreover, it boasts advantageous graceful degradation characteristics in case of faults at any of the inputs. Design examples realized in both coaxial and ridge waveguide resonators are then presented, as examples of the available RF/microwave technologies suitable for implementation. A proof-of-concept prototype was fully validated with fabrication and testing, demonstrating good results.