A 50-GHz SiGe Frequency Quadrupler With 42-dBc Harmonic Rejection and 17% Peak Total Efficiency

This letter introduces a highly efficient 50-GHz SiGe frequency quadrupler with exceptional harmonic rejection capabilities. Utilizing a design comprised of two consecutive doublers, it features a truly symmetric transformer balun with LC matching topology and ensures maximal rejection of odd harmonics with high total efficiency. The transformer balun achieves remarkably a low amplitude imbalance of 0.03 dB and a phase imbalance of 0.3° within the 3-dB fractional bandwidth from 48 to 52 GHz and exhibits a minimum harmonic rejection ratio (HRR) of 42 dBc from the fundamental to the seventh harmonic. The device delivers a peak output power of 5.4 dBm at an input power of 1 dBm, maintaining a high peak total efficiency of 17%. According to the best of authors' knowledge, this represents the highest HRR and total efficiency found to date among all E-, U-, V-, and W-band frequency quadruplers.