A PVT-Tolerant >40-dB IRR, 44% Fractional-Bandwidth Ultra-Wideband mm-Wave Quadrature LO Generator for 5G Networks in 55-nm CMOS

Abstract

Precise generation of quadrature signals over a wide frequency range is a key function for the next-generation 5G communication systems. In this paper, we present a wideband quadrature generator based on a single-stage polyphase filter (PPF). A phase detector senses the phase error from quadrature signals generated by a single-stage PPF, and a feedback circuit continuously tunes the filter center frequency to the input signal frequency by varying the polyphase resistance of an nMOS device in triode. Transformer-based resonant circuits at the input and output of the PPF ensure wide bandwidth and low loss. Prototypes have been realized in a 55-nm CMOS technology. Tailored to the next-generation 5G systems for cross-network interoperability requirements, the measured quadrature generator shows an image rejection ratio IRR > 40 dB over a bandwidth from 28 to 44 GHz. The power consumption is 36 mW for the PPF and buffers, and 3 mW only for the calibration loop. One key aspect of the proposed solution is its robustness over process, voltage and temperature (PVT), one of the weak aspects of alternatives proposed in the literature. This solution compares favorably with the state of the art and shows the largest fractional bandwidth (44%) among the quadrature generators at frequencies greater than 20 GHz, to authors' knowledge.