A 1GHz configurable chirp modulation (CM) direct digital frequency synthesizer (DDFS) is presented and implemented in 65nm CMOS technology. This DDFS is designed to generate 70-86MHz chirp signal for X-band frequency modulated continuous wave (FMCW) radar system. The proposed design is composed of 64-bit frequency control word (FCW) serial peripheral interface bus (SPI) supported 20-bit frequency/phase accumulator and 10-bit linear/non-linear hybrid digital-to-analog convertor (DAC). This DDFS supports saw-tooth chirp mode and exhibits 20-900 μs time of chirp duration (TCD) and 1ms pulse recurrence frequency (PRF), dissipates 24mW@1GHz clock from a 1.2V supply. The DDFS core occupies 180m170m area.