Joint Active and Passive Beamforming for IRS-Assisted Radar

Intelligent reflecting surface (IRS) is a promising technology being considered for future wireless communications due to its ability to control signal propagation. This paper considers the joint active and passive beamforming problem for an IRS-assisted radar, where multiple IRSs are employed to assist the surveillance of multiple targets in cluttered environments. Specifically, we aim to maximize the minimum target illumination power at multiple target locations by jointly optimizing the active beamformer at the radar transmitter and the passive phase-shift matrices at the IRSs, subject to an upperbound on the clutter power at each clutter scatterer. The resulting optimization problem is nonconvex and solved with a sequential optimization procedure along with semidefinite relaxation (SDR). Simulation results show that additional line-of-sight (LOS) paths created by IRSs can substantially improve the radar robustness against target blockage.

I. Introduction

In Recent years, intelligent reflecting surface (IRS) has attracted significant attention for wireless communication [1]–[5]. IRS is a planar array consisting of dozens of low-cost passive elements, which are capable of changing the phase and polarization of the impinging signals, thereby collaboratively achieving controllable signal reflection. Unlike existing approaches that modify the wireless link at the transmitter/receiver, IRS can be employed to realize programmable wireless channels between them, thus offering additional degrees of freedom for system design [6].