Microwave photonic radar for distance and direction measurement of multiple targets

Abstract

In drone detection and short-range automotive radar, the detection system should have the ability to monitor a large area and to detect the distances and directions of multiple targets. Suffered from electronic bottleneck, it's difficult to achieve a high-performance detection via conventional radar system. Microwave photonics has the advantages of low loss, large bandwidth and so on, and greatly improves the performance of radar system. To realize simultaneous distance and direction detection, microwave photonic phased array radar steers the beam for inertialess and squint-free scanning to detect targets from different directions. However, limited by the narrow angle scanning range, its field of view is inadequate. Photonicsassisted AOA (angle-of-arrival) detection method can detect the direction of target in a large-angle range. Nevertheless, it can hardly obtain the distance information of targets. It is a key issue to preform wide-angle simultaneous detection of distances and directions for multiple targets. We introduce a microwave photonic radar for distance and direction measurement of multiple targets. At the transmitter, a linear frequency modulation signal is generated by photonic frequency doubling and transmitted for detection. At the receiver, echo signals are received by a uniform linear array with three antennas. The intermediate antenna supplies overlapped reference spectra by polarization-multiplexing modulation.The de-chirped spectra possess specific symmetry, thus de-chirped frequencies of each antenna are clearly distinguished and distances and directions of multiple targets can be obtained. Two-target proof-of-concept experiments have verified that the average measurement errors of distance and direction are 2.4 cm and 0.6°, respectively.