Applied Mechanics and Materials Vols. 239-240

Abstract: The methods of radar target tracking have a substantial effect on the accuracy of the whole radar systems. The basic principles and implementing steps of the Extended Kalman filter (the EKF) and the Unscented Kalman filter (the UKF) are briefly introduced. The main sources of radar observation errors and the limitation of the current methods are analyzed. According to the requirements of tracking a CV target, the EKF and the UKF are used to simulate the experiments by establishing the specific model of radar target tracking. The results show that the tracking errors can be constrained within a certain range and the whole systems also have the high tracking accuracy.

Abstract: In order to solve the problem of loosing lock in weak GPS signal tracking, Kalman filter based carrier tracking method is presented.In this paper,two methods to track the GNSS carrier are compared,one is base on normal Kalman filter, another is based on square-root Kalman filter. The paper analyzes the under performance in the low carrier-to-noise ratio, and the expenditure of the actual project exists, but the high carrier to noise less discussed than the case will appear.The analyse and simulation result can be used to guide the engineering design of the GNSS receiver.

Abstract: This paper presents an algorithm of sea clutter suppression using graphics processing unit (GPU) to meet the real-time requirement in the general radar terminal system. The main idea is to convert an infinite impulse response (IIR) filter to a finite impulse response (FIR) filter, which is suitable for the parallelization processing of GPU. Finally, the converted FIR filter algorithm is implemented on the GPU efficiently, achieving a speed approximately twice as fast as that of the previous IIR filter algorithm implemented on the CPU.

Abstract: The conducted EMI problem caused by grounding net impedance has attracted more and more attention in resent years. In this paper, a model of interference system including parasitic capacitance was built. The theoretical feasibility of the measure and the mechanism of the conducted EMI caused by grounding loop were discussed. An improved design of conducted EMI suppression was proposed. Finally, a 100W (20V5A) SMPS was built to verify the effectiveness of this theory and the experimental results were also demonstrated.

Abstract: Spoofing is more malignant to GNSS receiver than noise jamming, both military and civil GNSS users need to detect and avoid spoofing. This paper presents a novel spoofing mitigation method based on multi-antenna receiver architecture. The algorithm strengthen the authentic signals in noise jamming environment, and the algorithm will place null in the direction of spoofer and reset the receiver to tracking the authentic signals when spoofing attack successfully. The rule to distinguish spoofing signal from authentic signal is spoofing transmitters often transmit several signals from the same antenna. The strategy and performance of the proposed method is independent of the spoofer’s complexity and ability. Computer simulation confirm the availability of the algorithm.

Abstract: The multidimensional Discrete Wavelet Transform (DWT) has been widely used in signal and image processing for regularly sampled data. For irregularly sampled data, however, other techniques should be used including the Least Square Wavelet Decomposition (LSWD). The commonly used level by level (sequential) wavelet decomposition, which calculates the wavelet coefficients in each resolution separately, may result in a gross interpolation error. To overcome this drawback, a different approach called the Simultaneous Least Square Wavelet Decomposition, which computes all wavelet coefficients simultaneously, have been proposed by the authors. In this paper, we extend the simultaneous LSWD approach to the multidimensional case and show that this method has excellent reconstruction property for two dimensional irregularly spaced data.

Abstract: Abstract: When a digital medical image is enhanced by Histogram Equalization, Homomorphic Filtering or multi-scales Retinex, the useful details of the image can not be strengthened. According to the imaging principle and medical requirement, a new method is proposed. The image is decomposed into illumination and reflection by wavelet illumination-reflection model. The details of the reflection are strengthened by soft-threshold method. The dynamic range of the illumination is reduced by Gaussian filtering in order to enhance the image. Experiments and analysis show that the method is obviously better than these algorithms.

Abstract: Based on wet paper code, integer wavelet and matrix coding, this paper constructs a new steganographic algorithm. Combine with the advantage in integer wavelet domain, which more close to HVS, a part of secret messages are embedded by LSB in high-frequency coefficients after integer wavelet switch, wet paper code is used to change the direction of embedding. Another part of secret messages are embedded by matrix coding in low-frequency coefficients after integer wavelet switch, wet paper code is still used to change the direction of embedding. The performance of the proposed approach shows that security and capacity of secret messages are improved in integer wavelet domain.

Abstract: The high dimension and complexity of feature descriptor of Scale Invariant Feature Transform (SIFT), not only occupy the memory spaces, but also influence the speed of feature matching. We adopt the statistic feature point’s neighbor gradient method, the local statistic area is constructed by 8 concentric square ring feature of points-centered, compute gradient of these pixels, and statistic gradient accumulated value of 8 directions, and then descending sort them, at last normalize them. The new feature descriptor descend dimension of feature from 128 to 64, the proposed method can improve matching speed and keep matching precision at the same time.

Abstract: In Shuping area, it is difficulty to find enough nature coherent targets to use InSAR technique to monitor the landslide. In order to solve the problem, CRs(Corner Reflectors) were used to improve the effectiveness of this technology. In this article Pyramidal Corner Reflector, Asymmetric Cubic Corner Reflector, Double Direction Asymmetric Cubic Corner Reflector are designed. In order to achieve maximum reflection intensity of CR, it's attitude must be carefully adjusted to match with the SAR imaging parameters exactly. After the CRs were deployed, the strong echo signals can be retrieved from SAR images. Analyzing the SAR image peak signals to locate the CR is the premise of differential processing. Through image location and phase analysis of ASAR and RADARSAT-2, the CRs’ signals can be recognition certainly. During the data processing of ASAR and PALSAR, the CRs can be regarded as ideal coherence target points.