Enhanced range doppler mapping algorithm for passive GNSS based radar aerial target detection

Using GNSS (Global Navigation Satellite System) signal as signal source and applying the principle of radar for object detection is a non-contact and emerging object detection technology. However, due to the problems that weak signal and low resolution, the application of such technology in object detection is very limited. On the basis of the detection of moving targets in the air, this paper puts forward a SNR (signal-to-noise ratio) improvement scheme of RDM (range doppler map). In this paper, bi-static GNSS radar model is employed. The RDM of air target is obtained on the basis of direct and reflected signals. The proposed RDM SNR improvement algorithm mainly by successively deducting the noise term in GNSS signals, so as to improve resolution of RDM and accuracy of target motion state solution. Compared with the current noise reduction method, which mostly depends on the prior conditions such as background environment, this algorithm is more applicable, as it is mainly based on the characteristics of the signal. The RDM spectrum is obtained by simulating moving target detection. The algorithm shows that the image information entropy after noise reduction is 63.23% for GPS signal and 71.69% for Beidou signal, which lower than that before noise reduction.