-Gu Sun

Feasibility Study of Forward-Looking Imaging Radar Applicable to an Unmanned Ground Vehicle

This study describes the design and verification of short range UWB(Ultra Wideband) imaging radar that is able to display high resolution radar image for front area of a UGV(Unmanned Ground Vehicle). This radar can help a UGV to navigate autonomously as it detects and avoids obstacles through foliage. We describe the relationship between bandwidth of transmitting signal and range resolution. A vivaldi antenna is designed and it`s radiation pattern and reflection are measured. It is easy to make array antenna because of small size and thin shape. Aperture size of receiving array antenna is determined by azimuth resolution of radar image. The relation of interval of receiving antenna array, image resolution and aliasing of target on a radar image is analyzed. A vector network analyzer is used to obtain the reflected signal and corner reflectors as targets are positioned at grass field. Applicability of the proposed radar to UGV is proved by analysis of image resolution and penetrating capability for grass in the experiment.

Effective Detection and Suppression of Low-Amplitude Interference in FMCW Radars

As many radar systems are simultaneously operated with overlapping frequency bands, interference between systems inevitably occurs. Because interference can degrade radar performance, suppression of interference is a critical issue in radar systems. In this letter, a new interference detection and suppression method using a short-time Fourier transform and an adaptive notch filter is proposed. An experiment is carried out to validate the proposed method and the results demonstrate that the proposed method is suitable for application in real FMCW radars.

K-Band Radar Development for the Ground Moving Vehicle

This paper presents a K-band radar system installed on the ground moving vehicle to detect and track a high-speed target. The presented radar is separated into three search regions to satisfy a wide area detection and a limitation of the installing space of the radar, and each region performs detecting the target independently and tracking the detected target automatically. The presented radar radiating K-band FMCW waveform acquires range and velocity information of the target at the every dwell and receiving antenna of the radar is applied the multiple baseline interferometer to extract the precise angle information of the target. 3-dimensional tracking accuracy of the radar is 0.25 m RMSE measured actually through a fire experiment of an imitation target.

Small Target Detection in Infrared Images Using Particle Filter Track-Before-Detection

저해상도 적외선 영상에서 무인비행기 혹은 드론과 같은 소형표적을 탐지하기 위한 알고리즘을 기술한다. 저해상도 영상에서 소형표적은 잠시 동안 나타났다가 배경 속으로 사라지는 것을 반복한다. 이 경우 기존의 임계치설정 기반의 표적탐지 방법은 오탐지 확률이 높으며, 이런 단점을 극복하기 위해 파티클필터 기반의 탐지전추적 방법을 제안한다. 먼저 영상 시이퀀스에서 배경을 예측하고 입력영상과 배경영상의 차영상에 파티클 필터를 적용한다. 이 과정에서 공산비를 계산하기 위해 표적 템플레이트와 특정 영상영역과의 상관계수를 사용한다. 실험에서 하늘을 비행하고 있는 무인비행기에 대해 적외선카메라로 영상 시이퀀스를 획득하였고 제안한 방법을 이 영상 시이퀀스에 적용하여 표적탐지 성능을 입증하였다.

Ultra-wideband imaging radar to reveal obstacles concealed in vegetation to improve navigation of unmanned ground vehicles

To increase mobility of an unmanned ground vehicle (UGV), this study describes the use of forward-looking imaging radar applying ultra-wideband radar technology. If radar is able to visualize images with high resolution in front of a UGV, the radar can be used to support the vehicle by detecting obstacles through foliage. This system employs the multi-input/double-output configuration with two transmitting horn antennas to increase cross-range resolution. Also, two rows of physical receiving antenna arrays provide the height information of targets using an interferometer principle. For visualizing objects in front of the radar, the back-projection method is applied to the data acquired from the receivers. A field test is used to verify the effectiveness of the new radar system. The performance of the radar is proved experimentally by the analysis of image resolution, grass-penetrating capability, and target height information.

A Study on Bistatic SAR Imaging Using Bistatic-to-Monostatic Conversion in Wavenumber Domain

This study describes an omega-K algorithm for focusing bistatic synthetic aperture radar(SAR) data using bistatic-to-monostatic conversion. Bistatic SAR system considered in this study consists of a transmitting antenna and a physical array of several receiving antennas. The length of the physical array is identical to the SAR synthetic aperture. Unlike the monostatic case, an omega-K algorithm for the bistatic case is difficult to obtain the exact equation in the 2D wavenumber domain. The key of the proposed algorithm is converting the bistatic data into a monostatic one. The effectiveness of the proposed algorithm is proved by simulation and real measurement data.

A Study of Bi-Static Through-Wall Imaging Radar Using a Noise Waveform

This paper describes an imaging approach to detect targets behind a wall. To acquire the accurate information over the strong signals reflected by the wall and affected by multipath, a bi-static through-wall imaging radar using a noise waveform is proposed in this paper including the methodology of imaging the received signal. The complete derivation of the proposed approach is presented. And the result of tests is demonstrated to show the possibility of the proposed approach.

A Study on Block Processing Approach for Mono-Static Terrain Imaging Radar

This paper describes a block processing approach to detect targets in front of mono-static terrain imaging radar (TIR). It is difficult to employ several conventional imaging methods of the synthetic aperture radar(SAR) because the TIR is an ultra-wide-band(UWB) type of radar and employs a dechirp-on-receive process. To design an available imaging method, a block processing approach which conducts a range compression and an azimuth compression is proposed in this paper. The complete derivation of the proposed approach is presented. The results of simulations and field tests are demonstrated to show the performance and validity of the proposed approach.

Performance Comparison to Solve Angle Ambiguity Needed to Angle of Arrival Estimation in 2D Radar Interferometer

This study describes the performance comparison to solve angle ambiguity needed to angle of arrival estimation in 2D radiometer. There are three algorithms to solve its ambiguity such as phase-comparison monopulse method, digital beam-forming method and least square error of the phase difference in 2D radar interferometer. To estimate two direction angles, phase-comparison monopulse method is sequentially applied to azimuth and elevation direction. To analyze the performance of these methods, probability of solving angle ambiguity and execution time have been chosen as performance indexes. Through the Monte Carlo simulation, we have verified that phase-comparison monopulse method is most effective in real-time signal processing application.

Accuracy Improvement of the Estimated Angle Using Phase Averaging in Phase-Comparison Monopulse Algorithm

This study describes the accuracy improvement of the estimated angle using phase averaging in phase-comparison monopulse algorithm. In addition, to compensate the time-delay due to the phase averaging, we propose the time-delay compensation algorithm which uses the derivative of the estimated angle. These derivative is calculated by the curve fitting method. Using the real radar interferometer, we have verified that the phase averaging and time-delay compensation algorithms are effective in real-time signal processing application.