Abstract: Devices are described that combine or divide electromagnetic signal power using short-circuited parallel-coupled multiconductor transmission lines. Such devices include single-stage, multi-stage ‘traveling wave’, and multi-stage broadband filter structures. Electrically shorting each coupled conductor simultaneously provides thermal cooling from heat generated by RF dissipative loss. These features may provide a compact, thermally robust power combiner/divider covering 3:1 bandwidth or greater. The devices may be applicable to radar, electronic countermeasures (ECM), and communications transmitters.