Circuit and system techniques for reducing phase noise in frequency synthesizers, and cancelling phase noise effect in quadrature receivers are presented.

Phase noise performance of digital phase-locked loops (PLLs) is limited by the time resolution of time-to-digital converters (TDC). In contrast to TDCs in the past that concentrate on the arrival time difference between the divider feedback edge and the reference signal edge. Our approach extracts the timing information that is embedded in voltage domain. This approach not only achieves a higher time resolution, lower phase noise, but also consumes less power. A digital background calibration circuit is also presented to reduce the output spurious tones when the digital PLL operates under fractional-N divisions.

Ring Oscillators (ROs) have the advantage of small area, wide tuning range, and multiphase output. However, their higher phase noise and higher sensitivity to supply noise may seriously deteriorate the wanted signal in wireless receivers. To circumvent this non-ideality, a low overhead phase noise cancellation technique for ring oscillator-based quadrature receivers is presented. The proposed technique operates in background and extracts ring oscillator phase noise as well as supply-induced phase noise from the digital PLL. The obtained phase noise information is then used to restore the randomly rotated baseband signal in digital domain.

In recent years, the unsilenced band at 57~64 GHz frequency range has motivated the building of high-data rate radio systems targeting wireless personal area network (WPAN) applications. To address this demand, a low-noise wide-band integer-N PLL is presented which serves as the carrier generator of a 60 GHz heterogeneous transceiver. The PLL employs sub-sampling phase detection technique to achieve low-noise performance, and provides 48 GHz LO and 12 GHz IF carrier signals for the heterogeneous transceiver.