Millimeter-wave power-combining techniques

A review is presented of the different power-combining techniques which use IMPATT or Gunn diodes as active devices and the performance of these techniques, focusing on the millimeter-wave frequency range of 30-300 GHz. The tradeoffs of these techniques are evaluated and possible future trends are discussed. The types of combiners examined include resonant cavity combiners, hybrid and chain-coupled combiners, N-way nonresonant combiners, chip-level combiners, spatial combiners, and multiple-level combining. Also, several other types of combiners are briefly discussed, including the dielectric guide combiner, the push-pull combiner, the cap resonant circuit combiner, the planar waveguide combiner, and the distributed circuit combiner.