A Compact Broadband Power Combiner for High-Power, Continuous-Wave Applications

A compact broadband combiner with a high power capacity and a low insertion loss, which is especially useful for solid-state power sources where multi-way power synthesis is needed, was designed and experimentally investigated. The combiner could combine the microwave signals of sixteen terminals into a single one and was based on a radial-line waveguide whose circumferential symmetry benefited the amplitude and phase consistency of the combiner. Simulation and experimental results showed that the prototype device, designed for S-band applications, exhibited a reflection coefficient S-1,S-1 < -20 dB in the range of 2.06-2.93 GHz, which corresponds to a relative bandwidth of approximately 34.6%. At 2.45 GHz, the phase imbalance was +/- 4.5 degrees and the 16-way transmission coefficient was concentrated around -12.0 similar to-12.3 dB. The insertion loss of the device at ambient and elevated temperatures was simulated and experimentally verified, which is of importance for the design of similar high-power microwave combiners. High-power tests proved that even without enforced wind or liquid cooling, the device can handle continuous power (CW) of at least 3.9 kW, which can be much enhanced by taking regular cooling measures. The combined features of the designed combiner suggest promising applications for power synthesis in high-power, solid-state RF sources.