Minho Ga

In this paper, we present a novel signal processing method for video synthetic aperture radar (ViSAR) systems, which are suitable for operation in unmanned aerial vehicle (UAV) environments. The technique improves aspects of the system’s performance, such as the frame rate and image size of the synthetic aperture radar (SAR) video. The new ViSAR system is based on a frequency-modulated continuous wave (FMCW) SAR structure that is combined with multiple-input multiple-output (MIMO) technology, an

A new method for suppressing surface waves on a millimetre‐wave microstrip array antenna is presented. A 10 × 2 patch array antenna is designed at 77 GHz for W‐band radar applications. Complementary split ring resonator (CSRR) has been designed at 77 GHz, etched on the antenna ground plane. Simulation and experimental results are compared in terms of the gain and the side lobe level with and without CSRR. CSRR between series patch antenna array could suppress surface waves effectively so that th

The effect of look angle on the accuracy performance of fixed-baseline interferometric synthetic aperture radar is studied. It is shown that there exists an optimal look angle that minimizes the variance of the surface height estimate for a resolution cell, and it depends upon the system as well as surface parameters. Numerical analysis confirming the existence of the optimal look angle is presented

One of the prospective research topics in radar remote sensing technology is the methodology for designing an optimal radar system for high-precision two-dimensional and three-dimensional image acquisition of the Earth’s surface with minimal hardware requirements. In this study, we propose a single-pass interferometric synthetic aperture radar (SAR) imaging technique with only a single antenna for the estimation of the terrain height. This technique enabled us to obtain terrain height informatio

A readily computable formula to perform versatile analysis of the nonstationary pulse-to-pulse correlation properties of ocean altimeter returns is presented. Using this formula, the correlation coefficient and correlation interval depending on the reference time, sea state, and system parameters have been analyzed. The results have suggested that the pulse repetition frequency should adaptively be adjusted to the sea state to ensure precise altitude measurements.

Ultra-high resolution (UHR) radar imaging is used to analyze the internal structure of objects and to identify and classify their shapes based on ultra-wideband (UWB) signals using a vector network analyzer (VNA). However, radar-based imaging is limited by microwave propagation effects, wave scattering, and transmit power, thus the received signals are inevitably weak and noisy. To overcome this problem, the radar may be operated in the near-field. The focusing of UHR radar signals over a close

The method based on the dual-frequency correlation function of reflected signals is one of the effective approaches for sea wave height estimation in radar altimetry. This method, however, has been applied for relatively low-altitude flights. As shown in our early studies, for the estimation of the sea wave heights using the dual-frequency correlation function, it is necessary to synthesize the array antennas, which are perpendicular to the flight direction. In this paper, we derived the limitin

This paper analyses the autocorrelation function of return waveforms in high precision radar altimeters employing chirp-pulse transmit signal under the condition of near-nadir deviations of the antenna boresight axis. It is shown that in case of ultra wideband transmit signals providing very high time resolution the correlation function can be approximated by a product of two separate functions of time.

In the work we introduce novel approach to remote sensing from space for the estimation of sea wave heights with a spaceborne high precision two-frequency radar altimeter with nadir synthesis antenna aperture. Experiments show considerable reduction of the decorrelation factor of the correlation coefficient and so significant enhancement of the sensitivity of the altimeter for the estimation for the sea wave status.

In this article, the design of a small and light-weight antenna and transceiving experiments for W-band UAV-mounted synthetic aperture radar (SAR) is presented. The antenna requirements i.e. gain, beam width, and antenna dimension are determined from the parameters of the radar system under implementation in our lab. To meet the requirements, 24-by-4 SIW slot array antennas have been designed. The antenna design includes a waveguide-to-microstrip transition for connection to circuits and metal f

In this study, we describe the technique for deriving a digital elevation model (DEM) from a synthetic aperture radar (SAR) stereo image pair and apply it to an image pair over Kwanak-san in Seoul, Korea. This paper contains brief discussion of the use of stereo SAR to derive topographic data, description of the overall structure of the stereo SAR processing system, description of the site and SAR data used for the evaluation and the source of validation data, results of the stereo SAR processin

The measurement performance of the dual‐frequency correlation radar altimetry for the estimation of the sea wave heights is not as accurate in satellite as in airborne platform. Multi‐frequency sensing signals can be applied to obtain sea surface state information while maintaining sensitivity over wide range of sea wave turbulences from space. The proposed method uses a sensing signal with angle modulation with optimum modulation index of m = 4.5, which enables to obtain a spectrum from 11 harm

Abstract Synthetic aperture radar (SAR) raw data simulation, operating under various scenarios, and realistic environments, are necessary for analyzing and verifying the performance aspects of SAR systems and the various algorithms used in them. In this article, we propose a method to simulate the raw data generated by multiple‐input multiple‐output video synthetic aperture radar (MIMO ViSAR) from a speckled scene, using beat frequency division (BFD) frequency‐modulated continuous wave (FMCW). U

This study presents mathematical analysis and numerical modeling for the estimation of measurement errors of height estimation over the sea surface for a precision radar altimeter installed in a low altitude flying vehicle. Reflective properties of the electromagnetic signals from the sea surface are determined by the local backscattering patterns of the sea surface illuminated. The height estimation of the flying vehicle from the received echo signals at the output of its tracking system is the

At millimetre‐wave frequencies, the discrepancy between simulation and measurement comes from the relative permittivity tolerance and fabrication tolerance. This discrepancy can mainly cause resonant frequency shift. A tunable waveguide‐to‐microstrip transition for the W‐band antenna is proposed to overcome this discrepancy. A typical transition consists of a microstrip probe on a substrate and a waveguide back short in a fixed structure. The tunability has been designed by making a movable back