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The variable-phase ring oscillator (VPRO) and phase-locked loop (PLL) architecture for integrated phased arrays enables the elimination of mixers, power splitters/combiners and phase shifters and hence allows for compact and power-efficient implementations. This paper extends the architecture to ultra-wideband (UWB) applications through architectural and circuit innovations. The implementation of a wideband VPRO enables the generation of UWB signals through the PLL which are inherently phase-shifted to accomplish beam-steering. The VPRO operates at half of the desired frequency range, and a squarer is interposed between the VPRO and the power amplifier of each channel. This doubles the bandwidth and the inter-channel phase shift and enables the architecture to cover the ±180° phase-shift range required for full beam-steering coverage. In addition, a waveform-adaptive, tunable-narrowband design paradigm is introduced that greatly simplifies the design of UWB RF blocks. A fully-integrated, 4-channel, 24-27 GHz, phased-array transmitter, useful for vehicular radar applications, is implemented in 0.13 μm CMOS to validate these claims.