A $K$-Band Frequency Doubler in $0.15-\mu \mathrm{m}$ GaAs pHEMT with an Autonomous Circuit for Stability Analysis

In this paper, we present a $\boldsymbol{K}$-band frequency doubler using $0.15-{\mu} \mathbf{m}$ E-mode GaAs pHEMT with Gm-boosted technique. The input driving power decreases and the conversion gain enhances due to the boosted input voltage swing of the Gm-boosted technique. Furthermore, an autonomous circuit is employed for nonlinear stability analysis of the proposed frequency doubler, and the oscillation issue can be resolved. The chip size is $0.9 \times 0.8\ \mathbf{mm}^{2}$. As the measured output frequency is from 37 to 43 GHz, the proposed frequency doubler exhibits a conversion gain of 0.9 dB with an input power of 0 dBm, a 15% fractional bandwidth, and a maximum saturated output power of higher than 2 dBm. The circuit performance can be compared with the prior art, and the proposed design methodology can be applied for some nonlinear microwave circuits.