Huang Yulin

Radar angular superresolution algorithm based on Bayesian approach

Angular resolution is the key parameter of radar. Conventional means of increasing angular resolution are dependent on the size of the antenna aperture. In framework of maximum likelihood, this paper presents an iterative algorithm to restore the target location information and then to obtain angular superresolution. Theoretical analyses indicate that algorithm accelerates convergence speed and achieves angular superresolution efficiently, and computational burden is relatively small. Simulation results show that the algorithm can efficiently attenuate the effect of antenna pattern convolution and highly enhance angular resolution; test data results show an order of improvement in angular resolution over real aperture image, also confirm that the method could obtain angular superresolution.

Research on A novel fast backprojection algorithm for stripmap bistatic SAR imaging

In this paper, a novel fast backprojection (BP) algorithm for stripmap bistatic SAR is presented. This algorithm gets improvements from the perspective of beam form and the space relation between the flight path and the mapping areas. Comparing with the traditional BP algorithm, the fast BP algorithm has higher computational efficiency. Also, it keeps the advantages of the traditional BP algorithm, such as robustness, high imaging precision, small memory requirements in processor and parallel processing easily. The imaging results of point targets and the experimental data verify the advantages of the fast BP algorithm.

Synchronization Technology of Bistatic Radar System

A complete method of synchronization technology of bistatic radar using global position system (GPS) is presented. The time benchmark signal 1PPS was elaborately modified in order to increase the time synchronization precision. A very high time synchronization precision was achieved. Using the modified 1PPS to discipline the local VCXO, the reference frequency signal both achieve a high long term stability (LTS) and short term stability (STS) property. The experimental results show that the time synchronization precision of our synchronization system can be improved from plusmn100 ns to plusmn25 ns. Well, the STS reach 2times10-11/s and the phase noise is improved 20 dB comparing with the results

SAR Doppler frequency rate estimation based on time-frequency rate distribution

Time-frequency rate distribution (TFRD) indicates the characteristics of instantaneous frequency rate (IFR) of a signal. This paper proposed a method based on time-frequency rate distribution to estimate Doppler frequency rate by analyzing the linear frequency-modulated (LFM) characteristics of synthetic aperture radar (SAR) echo in the azimuth direction. This method can be applied to low signal-to-noise ratio (SNR) situation with high estimation precision. Simulation and practical results show the effectiveness of the method.

Vehicleborne bistatic synthetic aperture radar imaging

A complete vehicleborne Bistatic Synthetic Aperture Radar (SAR) imaging experiment is presented in this paper. Some new technologies were used to solve synchronization problems. An algorithm named the Glide Window Echo CFAR was used to realize time synchronization and collect the echo. High stable local oscillator was employed to achieve frequency and phase synchronization, and the PRF was adjusted adaptively in the Data Acquisition Device in the receive station. Finally, the Range-Doppler algorithm with range migration correction was using to image the certain scene successfully.

Research on airborne bistatic SAR squint imaging mode algorithm and experiment data processing

The parallel flight squint mode of airborne bistatic synthetic aperture radar (SAR) is discussed in this paper. The bistatic squint imaging mode (SIM) algorithm is used to solve the coupling between the range and the azimuth of this mode. Simulation results prove the availability of this algorithm. The bistatic SIM algorithm is also used to process the experiment data, and a well focused Bistatic SAR image is generated successfully. Comparing the generated image with the bistatic rang-Doppler (RD) algorithm, we can find that the result of bistatic SIM algorithm is much better than that of bistatic RD algorithm in the parallel flight squint mode.

New approach for improving Mutual Information in POLSAR image registration

Aiming at the problem that information source of similarity measure is limited to image intensity usually in multi-polarization SAR registration, we propose an improved Mutual Information(MI) based on the multiple correlation information between the same polarized channels (HH, W) in multi-polarization SAR images. In this method, by analyzing the correlation characteristics of three polarized channels in multi-polarization SAR, and using channel correlation information extracted from polarimetric covariance matrix, we compute MI in multi-polarization SAR to improve the similarity measure. Finally, the simulation results show that, in the multi-polarization SAR image registration, similarity measure information sources affect the performance of similarity measure. We compare the similarity measures with different information sources in curve sharpness and noise immunity. The results prove that the measure based on the correlation of the same polarized channels for multi-polarization SAR performs excellently.

A deramping based omega-k algorithm for wide scene spotlight SAR

Spotlight SAR accumulates large Doppler bandwidth to improve azimuth resolution. On condition of certain pulse reputation frequency (PRF), Doppler bandwidth accumulates at the cost of imaging scene. This is a classic tradeoff between azimuth resolution and scene size in spotlight mode. A novel algorithm is proposed here to break the restriction. Firstly, a deramping based method is presented through bulk data processing to finish azimuth Fourier transform under low PRF. Omega-k algorithm is then applied to focus the full image. This algorithm is free of classic restriction and requires PRF only larger than the instantaneous bandwidth. Its bulk data processing is efficiency with no sub-aperture or interpolation. In this case, this algorithm is qualified to wide scene spotlight SAR imaging. The effectiveness of this algorithm is demonstrated by point target simulation.

Precise time frequency synchronization technology for bistatic radar

Abstract A complete method of synchronization technology of bistatic radar using global position system (GPS) is presented. The pulse per second signal (1PPS) is elaborately modified to increase the time synchronization precision and keep loop locking. A very high time synchronization precision is achieved. Using the modified 1PPS to discipline the local OCXO, the reference frequency signal achieves both high long term stability (LTS) and short term stability (STS) properties. An algorithm, named phase abrupt change CFAR is presented to restrain the 1PPS phase abrupt change and keep loop locking. The experimental results indicate that this time and frequency synchronization method is effective and the time synchronization precision of the synchronization system can be improved from ± 100 ns to ± 25 ns. In addition, the phase noise is improved to 20 dB.

Analysis of Bistatic SAR Frequencey Synchronization

In this paper, a bistatic SAR echos mathematical expression with frequency errors is given, and the frequency error was analysed. Two types of frequency synchronization errors were considered. We analysed the different effects about imaging of bistatic SAR in the condition that the echo with different frequency errors. The analytical result is proved by simulation, it can be the reference for bistatic SAR system design