Simultaneous Range and Velocity Detection With Asymmetric Dual-Chirped Photonic Radar

Photonically-generated multiband dual or triangular chirped waveforms are widely used in estimating both the range and velocity of moving targets owing to their good range-Doppler resolution; however, their usage is limited due to the complexity involved in generating them and the requirement of high-speed analog-to-digital converters (ADC) and digital signal processing (DSP) for estimating the target's direction. We demonstrate the photonic generation of an asymmetrical dual-chirp waveform. We further demonstrate how this asymmetrical dual chirp can estimate range and velocity, eliminating the high-speed ADC and DSP requirements. An asymmetric dual chirp is generated through a dual-drive Mach Zehnder modulator at 10 GHz with up-chirp BW of 1 GHz and down-chirp BW of 2 GHz. The asymmetricity in slopes of the dual-chirp results in different detuned frequencies for the approaching and receding targets, resulting in simultaneous detection of the range and velocity of the moving target with a low bandwidth detector and electrical spectrum ananlyser. The efficacy of the asymmetric chirp waveform is evaluated by subjecting it to testing in an emulated environment, whereby the range and velocity are determined with a maximum error tolerance of 0.2 m in range and 0.25 m/s in velocity estimation. Moreover, the utilization of the asymmetric dual chirp has been demonstrated to show its effectiveness in determining the velocity of a slow-moving toy car.