$W$ -Band Backward Distributed Frequency Doubler Using GaAs 0.15- $\mu$ m pHEMT Process

A novel backward distributed frequency doubler is proposed showing a high output power level without buffer amplifiers. The position of the output port is reversed compared to a conventional distributed structure, and the lengths of the transmission lines are optimized to effectively multiply the frequency and remove the fundamental-frequency signal (
$f_{0}$
) without additional circuits such as a balun. Thanks to no need of buffer amplifiers at the final stage of the doubler, the proposed circuit was implemented using a low cost, 0.15-
$\mu \text{m}$
GaAs pHEMT process. The measured results show a peak conversion gain and saturated output power of −4.3 dB and 7.1 dBm, respectively, with a 12.3% fractional 3-dB bandwidth. The proposed frequency doubler exhibits a fundamental-frequency rejection of −23 dB at 96 GHz with a moderate chip size of
$1.0 \times 2.0$
mm
²
.