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Tuned ring oscillators are used to generate multiple phases of a sinusoid for a variety of applications including phased- array transceivers and clock and data recovery circuits. A variable-phase ring oscillator (VPRO) is presented that generates outputs with a controllable phase progression, enabling its use in a compact low-power single-chip phased-array transceiver architecture. The VPRO functionality is shown to be robust with respect to process and layout mismatches. This enables the implementation of integrated phased arrays with acceptable array performance even in the absence of mismatch calibration circuitry, which are essential in other phase-shifterless schemes such as coupled oscillator arrays. A prototype 24-GHz four-channel single-chip phased-array transceiver implemented in a 0.13-mum CMOS process is presented to validate these claims.