A 140–220-GHz Balanced Doubler With 8.7%–12.7% Efficiency

Abstract

In this letter, a 140–220-GHz balanced doubler with high efficiency is presented. To implement the proposed doubler, a taper-type balun is introduced based on a metal ridge, which features an exponential and $n$ -order sine power fitting function. Such a ridge with a slot feeds the input signal to the T-type diodes with the equal magnitude and reverse phase. Then, the second harmonic can be extracted by the metal fin-line transition. To ensure the second harmonic transmitting to the output port, an air bridge across the ridge is utilized, which is close to the diodes with a quarter-wavelength ( $\lambda $ /4) of the center operated frequency $f_{c}$ . Comparing to conventional doublers, the proposed design without substrate eliminates the dielectric loss and substrate parasitic for the enhanced efficiency with an extended bandwidth. To verify the above-mentioned mechanisms, a wideband doubler is fabricated and measured, which exhibits a good efficiency from 8.7% to 12.7% at 140–220 GHz.