A low-power FM-UWB receiver intended for short range communications in wireless sensor networks is presented in this paper. It utilizes an "approximate zero IF" architecture which combines a free-running ring oscillator as the RF LO with a modified delay-line demodulator. The main benefit comes from implementing the gain stages and the demodulator at the IF instead of RF, allowing significant power savings. Integrated in a 65nm CMOS technology, the whole receiver chain consumes 420 mu W from a 1V supply while achieving -68dBm sensitivity at the data rate of 100 kb/s.