Zhigang Su

A Novel Blind GPS Anti-jamming Algorithm Based on Subspace Technique

In this paper, a blind adaptive beamforming algorithm for Global Positioning System (GPS) is proposed, which combines the cyclic adaptive beamforming (CAB) algorithm with subspace technique. Compared with the CAB algorithm, the new algorithm can generate high gain toward the satellite direction and form the nulls in the directions of jammers by constraining both the weight vector and control vector of the CAB algorithm to the orthogonal space of the steering vectors of jammers. The proposed algorithm has the advantages such as no requirement of any knowledge of the transmitted signals and the satellite locations, fast convergence speed, and low computation complexity. Simulation results are provided to demonstrate the performance of the proposed algorithm

Wind shear signal simulation of the airborne weather radar

Wind shear is recognized by a major hazard during takeoff and landing of aircraft, which can be detected by airborne forward-looking weather radar. A high-fidelity wind shear model constructed by the Computational Fluid Dynamics software has been implemented in this study. The model is reasonably representative of the downward wind falling to the ground during the mature phase of the microburst wind shear. The results of the radar echo signal simulation based on the above wind shear model show that the distribution of the velocities has an obvious horizontal “S” shape. The simulated results demonstrate the typical characteristic of the microburst wind shear.

A Two Stage GPS Anti-jamming processor for Interference Suppression and Multipath mitigation

Global Positioning System (GPS) has found wide application in many areas. However, due to the low power of the received signal, GPS is susceptible to a variety of interferences and multipath. In this paper, a two stage GPS anti-jamming processor based on adaptive arrays is proposed. Firstly, the array received signals are projected onto the orthogonal subspace corresponding to interference to suppress interferences. Then the interference free signals are further processed by a conventional data-independent beamforming to enhance the GPS direct-path signal and mitigate GPS multipath signals. Simulation results are provided to demonstrate the performance of the proposed algorithm.

Adaptive anti-jamming algorithm based on the characteristics of the GPS signal

In this paper, a novel adaptive anti-jamming algorithm for Global Positioning System (GPS) is proposed, which uses the characteristics of the GPS signal. Firstly, the interference is suppressed by projecting the received signal onto the interference orthogonal subspace. Then, the interference- free signal is processed by cyclic adaptive beamforming (CAB) algorithm in order to enhance the GPS signal. Additionally, we make a brief analysis of the conjugate cyclic correlation (CCC) matrix under finite snapshots. And in the estimation of CCC matrix we introduce the Hankel approximation method which helps to improve the performance of the proposed algorithm.

A constant-beamwidth beamforming method for acoustic imaging

Wideband array signal processing is applied in many fields such as underwater acoustics, acoustic imaging, and comunication. So the design of the wideband constant-beamwidth beamformer is more and more important. Focused beamformer based on wideband focusing approach is an efficient method. It transforms the signal spaces at different frequencies to the common one using a focusing matrix. It has some advantages such as requiring only one array, computational efficiency and the ability to operate in multipath environments. However, the approaches have a higher requirement of the knowledge of signal arrival angles for the focusing matrix, or else the performance of this method will degrade badly. To overcome this shortcoming, a broadband constant-beamwidth beamforming based on focusing approach for acoustic imaging is proposed in this paper. It improves the robustness of focused beamformer by combining the idea of RCB. Here RCB not only plays the part of a good beamformer but also modifies the arrival angle information of the signal of interest (SOI) and yields the more accurate focused data from the corrected focusing matrix for the focusing preprocessor. Simulation results show the feasibility of the proposed method.

Two Amplitude Spectral Estimators with Rank-Deficient Covariance Matrix

In this paper, two nonparametric amplitude spectral estimators, which belong to the adaptive filtering-based approach, are proposed. In case of only several snapshots available, the filtering data, which is formed by weighting the snapshots with the traditional Fourier weight vector, contains more larger residual term besides the signal term at the frequency of interest. Those residual term dramatically reduce the accuracy of the spectral estimate at the frequency. By weighting the snapshots with Capon weight vector, the weighted data is slightly influenced by the other frequency components, and the corresponding filters perform better estimation accuracy and higher spectral resolution. Numerical examples are provided to demonstrate the performance of the new approaches

GPS smart jammer suppressin algorithm based on spatial APES

Smart jammer is one of the most threat interferences for the GPS receiver, so a smart jammer suppression algorithm is proposed in this paper, which combines spatial amplitude and phase estimation(APES) method and high resolution coherent subspace estimation method. The new method can resolve the problem that spatial APES is unable to cancel multiple coherent interferences, and also provide the accurate GPS signal estimate. Simulation results show that the feasible of the proposed method.

A space-frequency anti-jamming algorithm for GPS

In this paper, we proposed a space-frequency GPS anti-jamming technique with constant beamwidth. The proposed method sets up a new data model by Fourier transformation. On the basis of the new model, the optimal output SINR can be obtained by using Capon beamforming similar to the only spatial domain. Also, in order to obtain the distortless GPS signal, the beampattern with constant beamwidth is generated by focusing transformation technique.

Adaptive anti-jamming algorithm based on the spatial and temporal characteristics of GPS signal

In this paper, an algorithm is presented for adaptive anti-jamming in global position system (GPS). The proposed algorithm combines the subspace technique with the cyclic adaptive beamforming (CAB) algorithm so that it can suppress non-periodic jammers and/or those with different direction of arrival from the GPS signal simultaneously. Simulation results demonstrate the proposed algorithm can effectively suppress more complex jammers, even under very lower signal-to-noise ratio.

Design based on MCU for the echo simulator of the range extended target

It is important for the high resolution radar to design the simulator for generating the echoes of the range extended target. In this paper, a simulator design which is based on Micro Controller Unit (MCU) is proposed for generating the echoes of the range extended target. Because those echoes change rapidly and the corresponding period is longer, the high speed FIFO is selected as the data cache. In the idle time of system, waveform data is transferred from MCU to FIFO, whereas in the operating time of system it is transferred from FIFO to D/A converter at a high speed in order to output the waveform. The experimental results show the design can meet the purpose of the echo simulator of range extended target.