This paper introduces a new impulse-radio ultra-wideband (IR-UWB) technique, combined with pulse-width modulation (PWM), to be referred to as PWM-IR-UWB, for low-power data transmission. Power saving is achieved at the transmitted (Tx) side by reducing the number of transmitted pulses for each sample. Amplitude information is encoded in the time and modulated within a sampling period, similar to PWM. A pattern of narrow pulses is then transmitted at the edges of the PWM signal. Therefore, instead of transmitting pulses for each data bit using conventional digital encoding techniques, such as pulse-position multiplexing (PPM), only two pulses are sent in lieu of multiple data bits, resulting in significant power saving. On the receiver (Rx) side, narrow pulses corresponding to PWM edges are detected and a time-to-digital converter (TDC) recovers the digital data bits corresponding to the analog sample by precisely measuring the pulse width of the recovered PWM signal. We demonstrate the proposed method by post-layout simulation of a PWM-IR-UWB transceiver in a 0.13-μm mixed-mode CMOS process. The transceiver achieved 10 bits of resolution with 2.8 pJ/bit power consumption in the Tx when transmitting a PWM signal at 10 M samples per seconds (Sps), which is the equivalent of 100 Mbps data rate.