Qianqiang Lin

COHERENT PHASE COMPENSATION METHOD BASED ON DIRECT IF SAMPLING IN WIDEBAND RADAR

In order to eliminate the negative in∞uence of the rotational phase component (RPC) of target prominent scattering centres on the performance of Doppler centroid tracking (DCT) method, a coherent phase compensation method is proposed. The coherence of echo pulses sampled directly in intermediate frequency (IF) is flrstly analyzed and proved. Based on the coherence property, the proposed approach improves the translational phase component (TPC) estimation accuracy of DCT. Compared to the modifled Doppler centroid tracking (MDCT) algorithm, the proposed method achieves better phase compensation performance with simpler operations. Both the theoretical analysis and experimental results based on the real ISAR data prove the efiectiveness and e-ciency of the presented strategy.

A Channelization-Based DOA Estimation Method for Wideband Signals.

In this paper, we propose a novel direction of arrival (DOA) estimation method for wideband signals with sensor arrays. The proposed method splits the wideband array output into multiple frequency sub-channels and estimates the signal parameters using a digital channelization receiver. Based on the output sub-channels, a channelization-based incoherent signal subspace method (Channelization-ISM) and a channelization-based test of orthogonality of projected subspaces method (Channelization-TOPS) are proposed. Channelization-ISM applies narrowband signal subspace methods on each sub-channel independently. Then the arithmetic mean or geometric mean of the estimated DOAs from each sub-channel gives the final result. Channelization-TOPS measures the orthogonality between the signal and the noise subspaces of the output sub-channels to estimate DOAs. The proposed channelization-based method isolates signals in different bandwidths reasonably and improves the output SNR. It outperforms the conventional ISM and TOPS methods on estimation accuracy and dynamic range, especially in real environments. Besides, the parallel processing architecture makes it easy to implement on hardware. A wideband digital array radar (DAR) using direct wideband radio frequency (RF) digitization is presented. Experiments carried out in a microwave anechoic chamber with the wideband DAR are presented to demonstrate the performance. The results verify the effectiveness of the proposed method.

Implementation of a multi-waveband, high-precision, wideband waveform generator based on DDWS for antenna channel characteristics test

In practical radar systems, amplitude and phase distortion exists in antenna channels, which has a bad effect on subsequent signal processing. So, waveform generator is needed to launch signals covering radar waveband to make a channel test. Ensuring accuracy and bandwidth of the waveform generator is a fundamental requirement. Accordingly, this paper proposed a full flow of wideband waveform generation, including hardware design, parameter selection and pre-distortion correction. Direct digital waveform synthesize (DDWS) is done in the first, second, or third Nyquist region without analog frequency conversion, ensuring the quality of the waveform. And pre-distortion measures are taken to correct the waveform reconstruction error. The waveform generator designed in this paper has been successfully applied in a digital array radar (DAR) system, which can generate 500MHz bandwidth LFM signal, covering multiple waveband including 0.65 GHz-1.15 GHz, 1.25 GHz-1.75 GHz, 1.85 GHz-2.35 GHz, 2.45 GHz-2.95 GHz.

An efficient DOA estimation method for uncorrelated and coherent wideband signals

In this paper, a new direction of arrival (DOA) estimation algorithm is proposed when uncorrelated and coherent wideband signals coexist. The proposed method estimates the uncorrelated signals and coherent signals respectively at two different stages. It makes the method resolve more sources than the array elements. Compared with the coherent signal subspace method (CSSM), the proposed method does not require any initial DOA estimates, thus avoid errors brought by incorrect initial values. Simulation and experimental results validate the effectiveness of the proposed algorithm.

Research on FPGA timing optimization methods with large on-chip memory resource utilization in PCIe DMA

As a high speed serial communication protocol, PCI Express (PCIe) is widely used in data transmission. This paper realized direct memory access (DMA) transmission in PCIe Gen2 8× mode based on Kintex-7 FPGA, and mainly solved timing problems caused by on-chip data stream buffer with large capacity. Firstly, PCIe DMA control process is optimized. Secondly, the connection of FIFO and PCIe IP core is designed to realize DMA data stream transmission. Thirdly, two timing optimization method is proposed to solve the timing risks in FIFO internal delay path and FIFO rd_en control signal respectively. The first method connect various types of FIFO with pipelines. The second method uses a transmission waiting mechanism. Finally, 3.5MB data stream FIFO (90% FPGA memory utilization rate) can be realized without timing failing path in PCIe DMA transmission. The work of this paper has been successfully used in a wide-band direct sampling radar system.

Hardware design and implementation of fast DOA estimation method based on multicore DSP

In this paper, we present a high-speed real-time signal processing hardware platform based on multicore digital signal processor (DSP). The real-time signal processing platform shows several excellent characteristics including high performance computing, low power consumption, large-capacity data storage and high speed data transmission, which make it able to meet the constraint of real-time direction of arrival (DOA) estimation. To reduce the high computational complexity of DOA estimation algorithm, a novel real-valued MUSIC estimator is used. The algorithm is decomposed into several independent steps and the time consumption of each step is counted. Based on the statistics of the time consumption, we present a new parallel processing strategy to distribute the task of DOA estimation to different cores of the real-time signal processing hardware platform. Experimental results demonstrate that the high processing capability of the signal processing platform meets the constraint of real-time direction of arrival (DOA) estimation.

A hardware-efficient DOA estimation method based on digital channelization receiver

In this paper, we present a novel hardware-efficient direction of arrival (DOA) estimation method based on digital channelized receiver. The proposed method splits the wideband array output into multiple frequency sub-channels and estimates the signal parameters using digital channelization receiver. Based on the accurate signal parameters estimation, signals with different bandwidths are isolated reasonably. Different DOA estimation methods are used to signals with different bandwidths. The proposed channelization based method can improve the output signal noise ratio (SNR). It outperforms those conventional DOA estimation methods on estimation accuracy, especially in real environment. Simulations are presented to demonstrate the performance. The results verify the effectiveness of the proposed method.