An 85.5-to-94.5-GHz W-Band Fully-Symmetric Quadrature LO Generator with a Fast Quadrature Calibration Technique, Achieving Closely Matched 61-fs RMS Jitter and 41-dB IRR

This work presents a W-band fully symmetric quadrature LO (QLO) generator that produces I/Q outputs with closely matched low phase noise (PN) and accurate quadrature phase alignment. To overcome the structural limitations of conventional W/D-band QLO generators, the proposed design employs a cascaded architecture consisting of a low-jitter digital PLL (DPLL) followed by fully symmetric subsampling PLLs (SSPLLs). This symmetric structure inherently equalizes the PN of the I/Q outputs, while a DTC-based three-step fast quadrature calibrator—employing cross-sampling (CS) and direct phase-shift (DPS) techniques—achieves precise quadrature phase calibration within 200 ns. Fabricated in 28-nm CMOS, the proposed QLO generator achieves an RMS jitter of 61 fs (1k-100M) for both I and Q outputs and an image rejection ratio (IRR) of 41 dB