Frequency shift keying (FSK) signal has been widely used in modern radar systems. To intercept the FSK radar signal with a high interception probability, radar reconnaissance receiver should have an ultra-wideband receiving ability. The Nyquist folding receiver (NYFR) is a novel non-cooperative ultra-wideband receiver and it requires a small amount of equipment. When the FSK radar signal is intercepted by the NYFR, the corresponding output is a hybrid modulation signal. Therefore, it is necessary to investigate the parameter estimation of FSK radar signal intercepted by the NYFR. Herein, based on the NYFR using sinusoidal frequency modulation local oscillator (LO), the drawbacks of several existing parameter estimation methods are first analysed. To overcome these drawbacks, the NYFR architecture is improved by changing the LO modulation type to periodic linear frequency modulation. Then, based on the improved NYFR, a novel parameter estimation approach is proposed according to the LO modulation characteristics and the template matching rule. The proposed method is suitable for different kinds of common FSK radar signal code schemes and its computational load is low. At last, several simulation results show the merits of the proposed method.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Abstract-Among ship detection methods for SAR image, constant false alarm rate (CFAR) is the most important one. However, several factors, such as detector parameter and distribution of ocean clutter, affect the performance of CFAR detection. This paper proposes a novel hierarchical complete and operational ship detection approach based on detector parameter estimation and clutter pixel replacement, which is considered a sequential coarse-to-fine elimination process of false alarms. First, a simple barycentric algorithm is adopted to estimate target-window size, and the morphology method is used to estimate false alarm rate for CFAR detector. Second, a clutter pixel replacement approach based on the statistical features of sea clutter is presented to obtain statistically independent, stationary, and Weibull distributed random data for CFAR detector to remove all false alarms. Experimental results of the detection methods on a SAR image dataset show that the proposed approach is effective in reducing false alarms and obtains a satisfactory ship detection performance.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.