A 300 GHz SiGe Double-Balanced Passive Third Harmonic Mixer Using PMOS Varactors

This paper presents a compact 300 GHz double-balanced passive third harmonic mixer in a 130 nm SiGe BiCMOS process. In the 300 GHz band, traditional varactors have a low capacitance ratio, resulting in the poor performance of varactor-based passive mixers. In this paper, we proposed a high capacitance ratio varactor based on PMOS transistors and apply it to the design of a 300 GHz double-balanced passive mixer. The RF output power of the mixer is greatly improved by the proposed varactor. The mixer achieves a simulated maximum output 1dB compression point (OP 1dB ) of 0 dBm and maximum saturation power (P sat ) of 2.7 dBm at 325 GHz with a LO frequency (f LO ) of 75 GHz and LO power (P LO ) of 25 dBm. The conversion gain (CG) is -19 dB with 3 dB bandwidth from 285 to 335 GHz. Benefiting from the double-balanced structure, the IF-to-RF, LO-to-IF, and LO-to-RF isolation performance are better than 42 dBc, 52 dBc, and 40 dBc.