Wen Biyang

Adaptive cochannel interference suppression based on subarrays for HFSWR

The paper analyzes the characteristics of cochannel interference (CCI) in the high-frequency (HF) surface wave radar (HFSWR), which adopts the linear frequency modulated interrupted continuous wave (FMICW). CCI will influence all the range bins, including all the positive and negative frequencies, and the negative frequency range bins contain only the external interference information. Based on the above characteristics, we introduce a new adaptive coherent side-lobe cancellation (CSLC) algorithm based on subarrays that use the negative frequency range bin samples to estimate the interference covariance matrix and correlation vector. Experimental results confirm that the general and robust algorithm can achieve effective CCI suppression using the data recorded by the Ocean State Monitor and Analysis Radar (OSMAR2003, manufactured in 2003), located near Zhoushan in Zhejiang, China.The paper analyzes the characteristics of cochannel interference (CCI) in the high-frequency (HF) surface wave radar (HFSWR), which adopts the linear frequency modulated interrupted continuous wave (FMICW). CCI will influence all the range bins, including all the positive and negative frequencies, and the negative frequency range bins contain only the external interference information. Based on the above characteristics, we introduce a new adaptive coherent side-lobe cancellation (CSLC) algorithm based on subarrays that use the negative frequency range bin samples to estimate the interference covariance matrix and correlation vector. Experimental results confirm that the general and robust algorithm can achieve effective CCI suppression using the data recorded by the Ocean State Monitor and Analysis Radar (OSMAR2003, manufactured in 2003), located near Zhoushan in Zhejiang, China.

Sample rate conversion using Walsh-transform for radar receiver

Current SRC methods can consume a large fraction of the digital signal processor resources leaving limited computational power for other tasks. Reducing the computational requirements for SRC is a key element for the success and profitability of SWR systems. An efficient decimation architecture using Walsh transform for HF surface wave radar receivers is presented. The proposed takes into consideration the complexities of algorithm due to the relatively high data rate and the intensive filter operations involved in commonly used decimators, which substitute multiplication-addition for addition-subtraction imposed on filter. Performances illustrative are compared with that of other similar decimators. Experiments results show that the new decimators outperform others, which is suited for real time signal processing in DSP, such as ADSP2 1060.

Multi-Agent Based Intelligent Video Monitoring for Unattended Substation

Multi-agent based intelligent video monitoring of unattended substation is designed in this paper. Moving objects detecting and tracking methods are used to analyze video streams collected by remote-viewing system of unattended substation. Also, cameraspsila negotiation mechanism of moving objects tracking is designed according to multi-agent theory and technology, in order to extract route and figure characters of objects moving in whole unattended substation region, such as person and vehicle. All information gained by the system can be used to guard against theft and analyze quality of patrol, examine, repair, and other missions, and it will improve the infomatization, automation, and intelligentization level of unattended substation.

CIC filter theory in DDC and implementation by using FPGA

Cascade Integrator Comb(CIC) filter is the main part of the next generation High Frequency (HF) radar. This paper describes the key points of CIC theory in the Digital Down Conversion (DDC) module of a radar receiver, and takes advantage of the high flexibility and high density feature of Field Programmable Gate Array (FPGA) for putting forth to design the CIC filter by using FPGA. This paper provides particular insight into design by FPGA, which has advantages in high speed operation and simply structure. Some important and practical applications are given in this paper. The simulation result proves the validity and veracity. Because we can adjust the parameters freely according to our need, the CIC filter can be adapted to the next generation HF radar.

Super-resolution ocean surface current algorithm based on MUSIC for OSMAR2000

Owing to the decametric wavelength, a large aperture antenna array is needed for high frequency (HF) ground radar to obtain high angular resolution with conventional beam forming (CBF); for the case of a compact antenna or small aperture array, spatial super-resolution algorithms are used to get satisfactory angular resolution. Wuhan Universitys ocean state measuring and analyzing radar (OSMAR2000) is expected to real-time extract ocean surface current, wave and surface wind information at medium-range and long-range. To obtain long-range (i.e. 200 km) current mapping, the radar frequency must be selected in the lower region of the HF band, e.g. 7.5 MHz. Digital beam forming (DBF) is applied with the 120 m-long phased array to determine the bearings of the sea echo with 15/spl deg/ resolution for wave and wind extraction. The angular resolution is, however, too coarse for current mapping, especially when the ocean current detection range is as far as 200 km. Consequently, a super-resolution ocean surface current algorithm based on multiple signal classification (MUSIC) is developed for OSMAR2000. The relative theory basis, processing procedure and preprocessing and postprocessing associated with the algorithm are given. The comparison of OSMAR2000 measurements with the measurements from a current meter and the Seasonde system shows the ocean surface current algorithm based on MUSIC for OSMAR2000 can meet the requirements of the project contract successfully.

Ionospheric Interference Suppression in HFSWR

Over the past two decades, significant advances have been made in the use of high frequency surface wave radar (HFSWR) for remote sensing in an ocean environment. As one of the main outside interference, ionospheric interference may badly affect radars performance. An effective method for ionospheric interference suppression in HFSWR based on time-sharing coherent side-lobe cancellation (CSLC) is presented. Experimental results acquired with the HF system OSMAR confirm that the method can achieve effective ionospheric interference suppression, but not decreasing the strength of the first-order sea echo

Detection of the number of signals in super-resolution ocean surface current algorithm for OSMAR2000

Super-resolution ocean surface current algorithm based on MUltiple SIgnal Classification (MUSIC) is used for current mapping of Wuhan Universitys ocean state measuring and analyzing radar (OSMAR2000), in which MUSIC is applied to estimate the bearings of the first-order sea echo signals. The premise of MUSIC processing is that the number of signals is known in advance. In fact, the number of signals is unknown, and needs to be estimated from received data. In the case of discrete targets, the problem can be perfectly solved using information theoretic criteria such as the Akaike Information Criterion (AIC) or the Minimum Description Length (MDL) criterion. However, these criteria are proved unsuccessful for sea echo signals both in simulation and in actual application, since sea surface is essentially a continuum. Therefore, an ad hoc method of detection of number of signals, a bit different from the existent methods, is developed for the current algorithm of OSMAR2000. The underlying idea is to determine the number of signals based on the variance of MUSIC spectra structure under different candidate number of signals.

Some problems in general scheme for HF ground wave radar engineering

f in : Wuhan Daxue Xuebao (Ziran Kexue Ban) , 2001 ,47(5) : 5 1 3 ~ 5 1 8 ] S o m e P r o b l e m s in Genera l S c h e m e for HF G r o u n d Wave Radar E n g i n e e r i n g YANG Zi-jie, WU Shi-cai, HOU Jie-chang, WEN Bi-yang, SHI Zhen-hua (School of Electronic Information,Wuhan University, Wuhan 430072,Hubei,China) Abstract: Some important problems in the system design and development of the HF Ground Wave Radar ( G W R ) OSMAR2000 are discussesd, concerning 1) estimation of GWR detection capabil i t ies;2) frequency modulated interrupted continuous wave ( F M I C W ) and pseudo noise phase modulation; 3) means to oppress near-sea echos~ 4) broad-beam phased array antenna and digital beam forming (DBF) technique~ 5) echo signal processing and zero-frequency interfere restricting approaches; 6) forming mode of I /Q~ 7) elimination of distance overlap and Doppler frequency overlap. In the fieldwork in Chinese East Sea we found that by using 120 m long, 8 antenna in which one for transmitt ing and all 8 for receiving, OSMAR2000 can detect current more than 200 km away with 120 ~ augular coverage and angular resolutionin of 2 ~ to 5 ~ in the dayt ime, and wind and wave at the distance of 100 kin. Our next research will concentrate on antenna miniaturization and universal GWR hardware platform using software radio technique as well as improve inversion algori thm for wind and wave.

Impulsive Interference Mitigation in High Frequency Radar

An effective method for impulsive interference mitigation in high frequency (HF) radar based on the detect-excise-and-extrapolate idea is presented. The key to the methods success is suppressing the ocean clutter in the time domain prior to detecting the impulsive interference. The method performed well on ocean echo data acquired with the HF radar system OSMAR

The effect of phase noise on the remote sensing of ocean surface currents

This paper studied the phase noise effect on the range spectrum and Doppler spectrum measured by high frequency (HF) radar which was used for remote sensing of sea surface state parameters. The presence of phase noise in the master oscillator caused a widening of the range spectrum and clutter velocity spectrum, degrading the range and velocity resolution. In this paper, a practical phase noise model is presented, and based on it, the relationship between the phase noise power spectrum density (PSD) and cumulative phase noise is investigated. Then, the basic minimum requirements for the PSD are calculated to maintain radar performance. The results show that a commercial off the shelf oscillator can meet the phase noise requirements.