Design of a High-Isolation n-Way Power Combiner Based on a 2n + 1 Port Mode Network

This paper proposes a design method for high-isolation n-way power combiners based on 2n + 1 port mode networks. The scattering matrix of a 2n + 1 port mode network is obtained by rigorously deriving the voltage and current relations. Following the proposed method, a compact four-way coaxial power combiner based on a nine-port mode network is designed and fabricated. Measurements show that from 7.8 to 10.3 GHz, the return losses of the input and output ports are better than -18 and -21 dB, respectively, the isolation levels between the input ports are higher than 21 dB, the insertion loss for power combination is less than 0.2 dB, and the amplitude and phase imbalances of the power combiner are less than approximately 0.15 dB and 2°, respectively. The simulated results agree well with the measured results. Moreover, the combiner has compact cross-sectional dimensions of 1.2λ × 1.2λ. It is clear that the designed four-way power combiner is superior in terms of its compact cross-sectional dimensions, high degree of isolation, low return loss, low insertion loss, and output amplitude and phase imbalance, which make it well suited for solid-state power combination. In addition, the power combiner is easy to fabricate and assemble. The proposed method shows great potential for realizing multi-way power combination with high isolation, low return loss, and compact cross-sectional dimensions.