A Balanced Frequency Doubler Covering 140–220 GHz With an Efficiency of 6.8%–11.6%

In this letter, a full-band balanced frequency doubler covering 140–220 GHz range is reported. To feed the Schottky barrier diodes (SBDs) with a reverse phase, a novel inline waveguide-to-microstrip (WG-to-MS) transition is adopted, which is used as mode conversion and broadband balun simultaneously. The generated second-harmonic is extracted directly by a taper waveguide, which also serves as broadband output matching. Compared with traditional Erickson-style frequency doublers, the presented doubler not only possesses an inherent inline input–output configuration, but also eliminates the dielectric loss and transition loss at the output circuit with an expanded bandwidth. To verify the proposed concept, the doubler is fabricated and measured, which exhibits a conversion efficiency of 6.8%–11.6% across the whole 140–220 GHz band under 10–20 mW input power.