Synthetic virtual array processing of GPS sonobuoys for underwater target tracking

This paper explores the coherent processing of an array of GPS sonobuoys as an effective method for enhancing target tracking capabilities and improving the bearing estimation accuracy. The paper mainly focuses on underwater target detection using an array of DIFAR sonobuoys. Currently the bearing estimation of underwater targets using DIFAR sonobuoys field is based on individual element processing. However the low levels of signal to noise ratio (SNR) jeopardize the bearing estimation accuracy. The main factor influence the performance is imposed by the deployment strategy of DIFAR sonobuoys and is related to the inter-element distance between sonobuoys which may exceed the minimum distance requirement for array processing. Other factors are the inter-element distances changes over time as well as sonobuoys initial deployed constellation. In this research, we modified the conventional Bartellet beamforming technique in order to accommodate array processing of a group of GPS sonobuoys. Moreover the paper demonstrates the implication of employing virtual array synthesis method to eliminate the current processing limitations. The proposed methods were tested using simulated data developed for two different scenarios with different underwater environmental conditions. A comparative analysis is presented for Bartellet beamforming application on GPS sonobuoys field using current basic processing techniques versus array processing techniques based on the method proposed in this study. The results show that the proposed method is capable of enhancing the accuracy of target bearing estimation especially in cases of very low SNR. Merits and limitations of the proposed method is discussed and analyzed in this study.