A 3.5-4GHz FMCW radar transceiver employing a phase-domain oversampled ranging method is implemented in 0.18μm CMOS for short-range wireless sensor network (WSN) applications. To overcome the tradeoff between bandwidth and ranging resolution in the conventional FMCW radar, a digital phase rotator and a 1-bit ΔΣ TDC are utilized to realize the oversampled phase-domain ranging, achieving both wide capture range and fine resolution. The proposed ranging method is verified in the prototype FMCW transceiver hardware and the feasibility of sub-cm ranging capability is also demonstrated based on on-board modulation measurement.