A Fully Isolated N-Way Radial Power Combiner

A new passively isolated N-way radial combiner design is proposed. The design incorporates low-loss partially filled radial combiners with a passive peripheral isolation network, where coaxial termination loads are used as isolation resistors. To confirm real-world performance, a 16-way combiner operating at 4 GHz was manufactured and tested. The minimum isolation measured among peripheral ports is better than 27 dB over more than 30% fractional bandwidth (BW), and the average asymmetric peripheral port input reflection is below -15 dB over 50% BW. Simulation analyses show that such excellent peripheral port isolation and matching has a significant value in improving the graceful degradation of a system utilizing such combiners. The prototype also achieves a center port reflection coefficient magnitude below -18 dB over 45% BW, and the measured signal balances are ±0.2 dB and ±2°. The structure that forms the radial cavity and PCB housing was manufactured exclusively on manually controlled machinery, so the measured 1-dB insertion loss BW is approximately 25%.