In-phase power combining of submillimeter-wave multipliers

Submillimeter-wave multiplier circuits can either be optimized for maximum efficiency or maximum output power depending on the application. However, it is always desirable to have maximum output power without sacrificing efficiency. To accomplish this goal we have proposed and demonstrated in-phase power combining of submillimeter-wave multiplier chips. We report on the design, fabrication and characterization of a 260-340 GHz tripler that utilizes two mirror-image chips and produces a peak of 22 mW with 11% efficiency. This source is then used to drive a two-chip 790-950 GHz tripler. Preliminary results obtained from this LO chain are 0.7 mW at 890 GHz at room temperature. This technology advancement now makes it possible to extend the frequency coverage of multiplier based sources well into the THz range.