A fully integrated UWB-IR (ultra-wideband impulseradio) transceiver was developed for wireless body area networks. The transceiver includes all of the components required for the transceiver; a pulse generator and a power amplifier for a transmitter, an analog front-end circuit and analog-to-digital converters for a receiver, a base-band circuit, and a clock generator. The transmitter generates precisely shaped short impulses with a digitally controlled pulse generator. To reduce power consumption, analog circuits are operated intermittently. The most outstanding feature of the receiver is its low sampling frequency for reducing power consumption. The sampling frequency is as low as 32 MHz, which is the same value as the pulse repetition frequency. The prototype transceiver was fabricated in 0.18-μm CMOS process technology. The transmitter satisfies the Federal Communications Commission spectrum mask, and the transceiver achieves -77 and -68 dB sensitivity for 250 and 10 Mbps, respectively.