Research On Direction Finding Algorithm Of Broadband Signal Based On Long Baselines

In this paper, several key technologies of passive location in electronic reconnaissance areresearched, which include the direction finding of broadband signal and detecting location problem ofelectronic jamming source.A direction finding algorithm for broadband signal based on the time delay estimation method isproposed in this paper, which has a single-long baseline. It has a simple structure but has a highprecision on direction finding. The algorithm transforms the time delay estimation into frequencyestimation through time-frequency conversion, overcoming the restriction of baseline distance whichmust be less than half wavelength in traditional method. The performance of the direction findingimproved naturally with the receiver aperture increased. Simulation results show that the accuracy ofthe proposed method can be close to the best under conventional SNR condition.This paper also has a research on electronic jamming source. The mainly signal form ofelectronic jammer is broadband noise signal. With the particularity of the signal form, this paperrealizes the detection of noise signal in time domain through the square accumulation. Combiningwith the algorithm proposed before, the direction of arrival (DOA) estimation of single noise sourcecan be achieved with high precision, which indicated via the simulation data. Considering that thereare some jammers exist at the same time in the real battlefield, a method of multi-signal DOAestimation was proposed, combining with the high resolution spectrum evaluation MUSIC algorithm.And then, a signal number estimation method by making use of the feature of noise signal wasdiscussed. The simulation results show that the signal number estimation of multi-noise-signal and theDOA of each signal can be achieved under the certain conditions. In the end, a kind of multi-signalidentification method was discussed for mixed signal form, focus on the DOA estimation of linearfrequency modulation (LFM) signal under the noise signal interference. With certain conditions, it canrealize the DOA estimation of LFM signal accurately by using signal reconstruction andtime-delay correction.