A $Ka$ -Band SiGe Bootstrapped Gilbert Frequency Doubler With 26.2% PAE

This letter presents a Ka-band Gilbert frequency doubler (FD), in which the phase of the injected signal to switching transistors is adjusted to maximize the core conversion gain (CG) and power-added efficiency (PAE). It achieves a peak PAE of 26.2% and a peak CG of 21 dB at 28 GHz, without any output buffer. The FD provides a saturated output power of 11.9 dBm, a 3-dB bandwidth of 22-36 GHz, and a fundamental harmonic rejection of 32 dB. To the best of our knowledge, this FD achieves the highest CG and PAE among all reported Si-based FDs without output buffers.