Zhuang Wang

The troposcatter array signal receiving model and processing algorithm

Troposcatter array signal model and processing algorithm are of great importance when over-the-horizon passive reconnaissance is carried out with troposcatter. This paper studies on troposcatter array signal model, and the diffusion phase between different array elements is found after analyzing the inter-relationship of different array element transfer functions,. Moreover, when analyzing the diffusion phase change of different targets, it is known that the bigger the target azimuth angle is, the further the distance between the transmitting and receiving antenna is, the wider the target azimuth beam width is, the bigger the array element number is, then the more obvious the diffusion phase is. Finally, aiming at the characteristics of troposcatter signal model, this paper improves the MUSIC algorithm, and designs the array signal processing algorithm which can estimate the target spatial distance spectrum.

Time-frequency diffusion analysis for DOA estimation of tropospheric scatter signal

DOA estimation is a hot topic in tropospheric scatter radar target reconnaissance Over-The-Horizon (OTH). The received signal propagated through troposphere OTH is so weak because of strong loss, the classical MUSIC has been unable to effectively estimate angle. So we adopt Time-Frequency (TF) MUSIC, i.e., replacing the array covariance matrix of the classical MUSIC with Time-Frequency Distribution (TFD) matrix, which is suitable for the low Signal-to-Noise Ratio (SNR) condition. In order to effectively processing signal, the troposcatter signal characteristics should be modeled and analyzed. Firstly, we analyze troposcatter propagation loss, and further deduce the receiver output SNR to provide support for algorithm design. Secondly, considering that time, frequency diffusion in energy caused by troposcatter multipath fading, we derive time-delay and frequency-shift diffusion functions based on scatter transmission function. To be more specific, the diffusion characteristics are studied on the variations of the beam width, target distances etc.. Then we deduce the joint time-frequency diffusion function and coefficient from the above two diffusions. Affected by the diffusion, the TFD matrix will be distorted to degrade the algorithm accuracy. To utilize the characteristic, we propose a weighted scattering signal TFD matrix, where the weight matrix is derived from the joint diffusion coefficient, to prominent the scattering signal according to the matched filter theory. Then we can estimate exactly angle for the troposcatter signal using the weighted matrix.

OTH passive location based on the troposcatter signal group delay and beamspace MUSIC

The Over-The-Horizon (OTH) locating of radiation source can be realized by the troposcatter propagation of electromagnetic (EM) signals. This paper studies the troposcatter signal group delay for target ranging and proposes a modified beamspace MUSIC to estimate the arrival azimuth angle of the troposcatter signal. Finally, the OTH target can be located by the ranging and azimuth angle estimation results.

Troposcatter OTH passive sensing with Cohen's class distribution based on an equal-slope Hough transform

The tropospheric scatter mechanism is potentially valuable for over-the-horizon (OTH) passive sensing, two limitations of this mechanism as large propagation losses and scattering fading diffusion are analyzed. Based on the diffusion properties, the received signals are analyzed with a bilinear Cohens class distribution, of which the parameterization function (i.e. the kernel) is built from the diffusion coefficient to enhance the SNR. After that, target signals are focused in a parameter space by an equal-slope Hough transform (HT) with a priori information of the intra-pulse frequency interval, the focus-points can be effectively accumulated to detect the OTH targets.

Joint calibration of mutual coupling and channel gain/phase inconsistency using a near-field auxiliary source

A new indoor calibration method is proposed to estimate and compensate mutual coupling and channel gain/phase inconsistency parameters for a uniform linear array (ULA). This calibration method employs only one assistant source in near-field and is unnecessary to conduct complex feed circuits behind the antennas. Firstly, accurate channel gain/phase deviation is estimated via an inside testing structure exploiting the coherence of a single-frequency test signal. Then, the received array manifold of the near-field auxiliary source is modeled with a second-order Taylor series approximate. Finally, joint mutual coupling and gain/phase error are compensated using the inside testing results and modeled array manifold as the initialization of the eigenstructure (also called subspace) technique, which profoundly accelerates the convergence and guarantees the uniqueness of the converged solution. Experiments conducted on an actual 16-element ULA validate the proposed method.

A ships data association algorithm based on the ships formation structure and ships attribute information

In order to use the spaceborne optical imaging and electronic reconnaissance data to monitor the ships formation, this paper proposes a target association matching algorithm based on the structure of ships formation and targetspsila attribute. Simulation results that this algorithm delivers better performance compared to the traditional method, in the situation that because of the sensors are sparse sampling and the targets location precision are greatly different so that can not be established to creation the targetspsila motion model.