A 108-to-141.8GHz 27.1%-Tuning-Range Synthesizer Employing a Dual-Reference-FTL Sub-Sampling PLL and 3rd-Harmonic-Enhancement Class-F VCO and Injection-Locked Frequency Tripler

A sub-THz frequency synthesizer employs a cascade of a sub-sampling PLL featuring a frequency-tracking loop with dual co-prime sub-sampling factors for an infinite lock-in range, a 3rd harmonic-amplitude-enhancement class-F VCO, a harmonic-rejection-enhancement class-F ILFT, and a feed-forward locking-range enhancement. The proposed synthesizer measures 27.1% frequency tuning range from 108 GHz to 141.8 GHz with maximum output power of -22dBm, -3dB bandwidth of 25GHz while consuming 38mW.