This paper presents a primary impulse-radio ultra-wideband (IR-UWB) radar system for real-time short-range localization, e.g., for smart traffic and automotive applications. The radar system consisting of an integrated radar transceiver (TRx) using 45-nm SOI CMOS technology and an FPGA-based signal processing. The efficient transmitter (Tx), which complies with the regulations for both indoor and outdoor applications, modulates and emits a seventh derivative Gaussian pulse. In the receiver (Rx), echo signals will be amplified and sampled in real-time. The echo pulses are recovered by signal processing hardware on the FPGA, which is also used to perform simple classification tasks like user warning. The radar system is compact, portable, and power efficient. The Tx has a high-energy efficiency of 11p J. The proposed radar system achieves very high signal-to-noise ratio (SNR) and range precision. It has a maximum detection range of 15 and a range resolution down to 3cm. Moreover, a target of interest can be warned with a latency as fast as 16μ by using 1-bit real-time sampling.