A 1.2-V single-sideband upconverter system with high spurious suppression for UWB frequency synthesizers

This paper presents a precise single-sideband (SSB) upconverter system for use in UWB Mode 1 frequency synthesizers. A divide-by-two circuit and a notch filter are employed to generate accurate quadrature sinusoids at the required offset frequency with low harmonic distortion for precise SSB mixing. Double degeneration technique is applied to linearize the SSB upconverter for minimizing nonlinearities and unwanted spurs. Fabricated in a 0.18-m CMOS process, the SSB upconverter system achieves a high image rejection ratio of 50.2 dB at a low supply voltage of 1.2 V. The in-band and out-of-band spurious suppressions are at least 32 dB and 42 dB, respectively. Moreover, stable performance is obtained even under a 1-V supply.