Nearfield compensation method for obtaining quite precise expected response in broadband beamforming

When the signal source is within the nearfield of the receiving array, using the farfield assumption to design the beamformer will result in severe degradation in the beampattern performance. We now present a nearfield compensation method, which we believe can ensure quite precise expected response for arrays with more than 20 elements. In the full paper, we explain in some detail our nearfield compensation method and experimental results. In this abstract, we just add some pertinent remarks to listing the four topics of explanation. The first topic is; nearfield compensation. In the first topic, we perform error analysis and summarize the important results of this analysis in Fig.3 in the full paper. The second topic is: the experimental environment and computer simulation analysis. The third topic is; experimentally measured uncompensated broadband beampattern. In the third topic, we, with the help of Fig.7 in the full paper, point out that the mainlobe of the experimentally measured nearfield response is distorted, thus causing severe degradation in the beampattern performance. The fourth topic is: experimentally measured compensated broadband beampattern. In the fourth topic, we, with the help of Fig.8 in the full paper, point out that, with nearfield compensation, the mainlobe of the experimentally measured nearfield response is not distorted, thus ensuring the satisfactory performance of the constant beam-width beamformer. In both the third and fourth topics, the experiments were lake experiments carried out for a 32-element uniformly linear array.