• Ocean Systems Engineering
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• v.13 no.2
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• pp.195-224
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• 2023

This paper proposes a method for the acoustic imaging wherein the traditional requirement of the relative movement between the transmitter and target is overcome. This is facilitated through the beamforming acoustic array in the transmitter, in which the target is illuminated by the array at various azimuth and elevation angles without the physical movement of the acoustic array. The concept of beam steering of the acoustic array facilitates the formation of the beam at desired angular positions of azimuth and elevation angles. This paper substantiates that the combination of illumination of the target from different azimuth and elevation angles with respect to the transmitter (through the beam steering of beam forming acoustic array) and the beam steering at multiple frequencies (through SF) results in enhanced reconstruction of images of the target in the underwater scenario. This paper also demonstrates the possibility of reconstruction of the image of a target in underwater without invoking the traditional algorithms of Digital Image Processing (DIP). This paper comprehensively and succinctly presents all the empirical formulae required for modelling the acoustic medium and the target to facilitate the reader with a comprehensive summary document incorporating the various parameters of multi-disciplinary nature.

• Journal of the Korea Institute of Military Science and Technology
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• v.25 no.2
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• pp.144-150
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• 2022

The on-board processor of satellite synthetic aperture radar(SAR) generates transmission signal by digital signal processing, converts it into an analog signal. At this time, the transmission signal generated from the baseband requires the frequency modulation to convert it to the high-frequency band in order to improve the stability. General frequency modulation method using local oscillator(LO) causes IQ imbalance due to phase error/magnitude error and these error reduce performance of SAR. To generate transmission signal without phase/magnitude error, this paper suggests design method of the frequency modulation method using digital to analog converter(DAC) at on-board SAR. For design, this paper analyzes the characteristic of DAC mode and uses pre-compensation filter. To analyze the proposed method performance, performance index are compared with IQ imbalance signals. This method is suitable for on-board SAR using fast sampling DAC and has the advantage of being able to solve IQ imbalances.

• Journal of Satellite, Information and Communications
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• v.7 no.1
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• pp.75-81
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• 2012

This study is to design the transmitter and receiver of short range UWB(Ultra Wide Band) 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. The transmitter needs two transmitters to improve the azimuth resolution. Multi-channel receivers are required to synthesize radar image. Transmitter consists of high power amplifier, channel selection switch, and waveform generator. Receiver is composed of sixteen channel receivers, receiver channel converter, and frequency down converter, Before manufacturing it, the proposed architecture of transceiver is proved by modeling and simulation using several parameters. Then, it was manufactured by using industrial RF(Radio Frequency) components and all other measured parameters in the specification were satisfied as well.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.4
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• pp.451-458
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• 2014

This paper introduces a bistatic ISAR imaging technique. In bistatic geometry, the transmitter and receiver are placed in different locations. The monostatic ISAR is inadequate not only for obtaining images on targets approaching along the radar's line of sight, but also for stealth targets. In this paper, geometry, signal modeling as well as bistatic Doppler for bistatic ISAR are introduced to address these problems. Simulations results show bistatic ISAR images as well as monostatic ISAR images against target's moving scenarios, and analyze their differences for each scenario.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.8
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• pp.670-677
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• 2017

In this paper, we propose a rotational motion compensation(RMC) for bistatic inverse synthetic aperture radar(Bi-ISAR) imaging. For this purpose, geometry-error, caused by changes of bistatic-angle, is removed using known position information of a transmitter, a receiver, and target trajectories. Next, RMC is performed to compensate non-uniform rotational motion error by reformatting radar signal in terms of a newly defined slow time variable that converts non-uniform rotational motion into uniform one. Simulation results using an aircraft model composed of ideal point scatterers validate the efficacy of the proposed Bi-ISAR RMC method.

• Journal of electromagnetic engineering and science
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• v.2 no.1
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• pp.39-44
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• 2002

A high speed data link capability is one of the critical factors in determining the performance of the spaceborne SAR system with high resolution because of the strict requirement far the real-time data transmission of the massive SAR data in a limited time of mission. In this paper, based on the data lint model characterized by the spaceborne small SAR system, the high rate multi-channel data link module is designed including link storage, link processor, transmitter, and wide-angle antenna. The design results are presented with the performance analysis on the data link budget as well as the multi-mode data rate in association with the SAR imaging mode of operation from high resolution to the wide swath.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.10B
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• pp.1777-1784
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• 2000

In this paper we suggested the chirp stitching algorithm and transmitter/receiver channel to a spaceborne high resolution SAR which enables wideband signal generation and processing with minimum hardware requirement. The transmitter channel generates two sub-band signals and then generate a wideband signal using chirp stitching algorithm and the receiver channel divides a wideband signal into two sub-band signals in order to overcome the high speed data handling capability of this spaceborne systems. We generated and processed a 100 MHz wideband signal evaluated the performance and verified the feasibility of the application of this chirp stitching algorithm and transmitter/receiver channel to spaceborne high resoultion SAR.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.3
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• pp.326-329
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• 2016

UAVs(Unmanned Aerial Vehicle) can be used in variant fields fornot only combat, but also recon, observation and exploration. Moreover, UAVs capacity can be expanded to impossible missions for existing surveillance system such as SAR(Synthetic Aperture Radar) technology that collecting images from all weather conditions. In recent days, with development of highly efficient IC and lightened system technology, there are significant increase of researches and demands to make SAR sensor as a payload of UAV. Therefore, this paper contains development process and results of small signal generator and RF device as a core module of SAR system based on the digital device of DDS.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.9
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• pp.707-721
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• 2018

In this paper, a small synthetic aperture radar(SAR) system with 30 cm resolution is proposed, and a RAW data-based Doppler parameter estimation and motion compensation algorithm is described in detail. Acquisition of both PolSAR and InSAR data are enabled because there are two channels each in the transmitter and receiver modules. Automotive-based field work is performed to obtain PolSAR data, and signal processing results are ultimately obtained. A motion compensation algorithm is used to mitigate the residual phase error due to platform oscillation, and improved performance is obtained with the motion compensation algorithm using the automotive field test data.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.165-166
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• 2008

Bistatic spotlight synthetic aperture radar(BSSAR) with single track configuration uses the transmitter and the receiver which travel along the single track such as the leader-follower. For the BSSAR imaging, we modify the range migration algorithm. In time domain, we make the monostatic SAR using shifting of path, Then, in frequency domain, we compensate the separated distance between the scene center and the flight path using the principle of the stationary phase (PSP).