This paper describes a waveform generator for 77 GHz automotive radar systems based on a fractional N-Phase Locked Loop (N-PLL) with a third-order delta-sigma (ΔΣ). A control unit is used to control the ΔΣ modulator to vary the output frequency. The behaviour of the generation is simulated in Simulink and ten output frequencies with a slight difference are generated. The proposed generator has the potential to generate a very small frequency difference with the flexibility in frequency shift, which is a good choice in limited bandwidth cases like automotive radar systems.