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Bao Z.,Key Research Laboratory of Wuhan Early Warning Institute | Chen J.-W.,Key Research Laboratory of Wuhan Early Warning Institute
IET Conference Publications | Year: 2015

It is required for the Cognitive Over-the-Horizon-Radar (COTHR) to deepen the cognition of the ionosphere environment. The current model of the ionosphere structure cannot satisfy this requirement. In this paper, the dispersion effect is introduced into the ionosphere fine structure and the space-time-frequency fine structure model of the ionosphere is proposed. Simulation results testify the validity of the model. Source


Zhao Z.-G.,Key Research Laboratory of Wuhan Early Warning Institute | Chen J.-W.,Key Research Laboratory of Wuhan Early Warning Institute | Bao Z.,Key Research Laboratory of Wuhan Early Warning Institute
Tien Tzu Hsueh Pao/Acta Electronica Sinica | Year: 2012

To enhance transmitting power efficiency in element-space multiple-input multiple-output (MIMO) skywave over-the-horizon radars (OTHR), a reduced dimension time diverse beamspace MIMO-OTHR scheme is proposed, and transmitting adaptive digital beamforming is realized under the scheme. With the new scheme, the stored power in invisible beamspace is decreased without acute fluctuations in beam pattern, and little reduction of degree of freedom makes MIMO-OTHR be able to work under the situation that the number of multipath clutters is large. The new scheme needs only beam direction control, which simplifies the MIMO realization in OTHR. Theoretical analyses and simulation results both show that the presented scheme is effective. Source


Luo H.,Key Research Laboratory of Wuhan Early Warning Institute | Chen J.-W.,Key Research Laboratory of Wuhan Early Warning Institute | Bao Z.,Key Research Laboratory of Wuhan Early Warning Institute
2012 10th International Symposium on Antennas, Propagation and EM Theory, ISAPE 2012 | Year: 2012

In over-the-horizon radar (OTHR), radar signals are subjected to ionosphere perturbation as they propagate through the ionosphere, and the weak echo signal from the low-speed target is almost masked by the spreading of Bragg peak. In order to acquire the spread sea clutter accurately, sliding window band-pass filters is proposed to extract the first order clutter (calibration signal), which can realize adaptive selection of the filter bandwidth. At the same time, a novel algorithm named Covariance Matrix Solving method (CMS) is presented to correct ionospheric phase contamination. Theoretical analysis and real data processing indicate that CMS method has a good performance and can obtain a better correction effect than Phase Gradient Autofocus (PGA) method. © 2012 IEEE. Source


Yan T.,Key Research Laboratory of Wuhan Early Warning Institute | Chen J.-W.,Key Research Laboratory of Wuhan Early Warning Institute | Bao Z.,Key Research Laboratory of Wuhan Early Warning Institute
IET Conference Publications | Year: 2015

Multi-mode propagation usually happens in Skywave over-the-horizon radar (OTHR) due to the Multi-layer physical structure of the ionosphere, resulting in sea clutter spectrum being broadened, which seriously affects the performance of ship targets detection for OTHR. Existing methods for solving multi-mode propagation work badly in the condition of the ionosphere nonlinear disturbance or short coherent integration time (CIT) because of inaccuracy of parameters estimation. Basing on 2-D arrays adaptive beamforming, this paper studies a new ship detection method for OTHR under multi-mode propagation. Firstly, the basic principles of multi-mode propagation for OTHR and the influences on ship detection are elaborated, and the performance deficiencies of existing solutions are analysed; Secondly, OTHR echoes model under multi-mode propagation is established, and a robust adaptive beamforming method is proposed according to echoes characteristics; Finally the experimental simulations are given, simulation results verify the effectiveness of the proposed algorithm. Source

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