A Coherent Spurious Analysis for Sub-THz Frequency Multiplier Chains

At sub-THz frequencies, the local oscillation for transceivers is often generated by an analog frequency multiplier tree. This paper studies the origins and minimization of spurious tones in a local oscillator multiplier consisting of a chain of frequency doublers. It is found that the nearest spurious components depend on the leakage of the input signal in the first multiplier, which can be minimized by active bias tuning, filtering in the first stage or better balance in the driving differential signal. To verify the nonlinearity modeling, 0.13-μm SiGe BiCMOS technology has been utilized.