In this paper we present a 77-GHz software defined orthogonal frequency-division multiplexing (OFDM) radar. A single channel RF frontend equipped with a 77-GHz SiGe chip which includes an integrated IQ modulator in the transmit path and an IQ receive mixer is used for range and range/Doppler measurements. Digital-to-analog converters (DACs) with a sampling rate of 500MSPS and 14 bit resolution are used to generate OFDM symbols with 201 sub-carriers and a bandwidth of 200 MHz. Sampling of the received signal is realized by analog-to-digital converters which, like the DACs used to generate the TX signal, run at 500MSPS and deliver a resolution of 14 bit. The performance of the overall system was optimized by a peak-toaverage power-ratio reduction technique. A standard deviation of 12.4mm was achieved for range measurements which were carried out in an anechoic chamber. Furthermore, first test measurements demonstrate that the system can be applied to moving target scenarios.