This paper considers the beamforming optimization for sensing a point-like scatterer using a bistatic multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) radar, which could be part of a joint communication and sensing system. The goal is to minimize the Cram\'er-Rao bound on the target position's estimation error, where the radar already knows an approximate position that is taken into account in the optimization. The optimization allows for beamforming with more than one beam per subcarrier. Optimal solutions for the beamforming are discussed for known and unknown channel gain. Numerical results show that beamforming with at most one beam per subcarrier is optimal for certain parameters, but for other parameters, optimal solutions need two beams on some subcarriers. In addition, the degree of freedom in selecting which end of the bistatic radar should transmit and receive is considered.

翻译：本文考虑利用双站多输入多输出（MIMO）正交频分复用（OFDM）雷达（可归属于联合通信与感知系统）对点状散射体进行感知时的波束赋形优化问题。优化目标是最小化目标位置估计误差的克拉美-罗下界，其中雷达已知近似位置并纳入优化考量。优化允许在每个子载波上采用多波束赋形。针对信道增益已知与未知两种情况，讨论了波束赋形的最优解。数值结果表明：当某些参数设置下，每个子载波最多使用一个波束的赋形方案即为最优；但在其他参数条件下，最优解需在部分子载波上使用双波束。此外，还考虑了双站雷达收发端选择自由度对优化的影响。