A UWB RF detector employs a pulsed self-oscillating mixer (SOM) and an output integrator to provide low-noise preamplification, mixing and sampling. The SOM produces short-burst, microwave self-oscillations that are phase-locked to a clock. The self-oscillations are used for mixing. The SOM can also radiate UWB RF pulses. A one-transistor SOM can simultaneously implement both a UWB emitter and a UWB detector in a radar transceiver. A control loop can stabilize the self-oscillations at nanowatt levels. Nanowatt UWB radars and radios can be realized, thereby opening new spectral bands beyond those formally designated for UWB operation.