Abstract: A precise bearing method of digital split-beam array system is considered in this paper. This method is based on the principle of time delay estimation in terms of cross-spectrum of input data, which is proposed by A. G. Piersol. In the case of array processing there are more than two elements. We have to find the equivalent acoustic center. For a line array, the equivalent acoustic center is independent of frequency. But for a circle array the center is dependent on frequency. We derived a simple formula for circle array in the case of small incident angle. The precise value of angle of incident signal can be calculated directly from input data.
The estimation bias depends on the length of DFT, sampling frequency and the number of accumulation. Some measures for improving the accuracy of angle bearing are described in this paper. One method is to weight the estimation value in each frequency bin of DFT in terms of their power spectrum values. In some cases it has been proved that choosing a suitable dow is an efficient method.
The block diagram of digital split-beam system is illustrated. Some results simulated in computer are presented. For a digital sonar it is possible to track more than one targets simultaneously by using the method described in this paper.