This paper describes the W-band fully polarimetric radiometer design and the measurement results of material's emissivity of rubber sheet and water as examples using developed radiometer. The measured brightness temperatures of sample materials depend on incident angle. For this angle dependent measurement, the test set-up was designed. Using the measured brightness temperature, the characteristics of material like emissivity and dielectric constant can be retrieved. Finally, the comparison between theoretical value and measurement value are also listed in the paper.

In this paper, we developed and experimented of the W-band 1-D focal plane array (FPA) passive imaging radiometer which was called by Millimeter-wave Imaging Radiometer Equipment (MIRAE). This consists of quasi-optics including a dielectric aspheric lens and a metal mirror as a reflector, 30 channels FPA receiver based on the direct conversion type, scanner, image processor and displayer. To get 2-D radiometer image with 1 Hz frame rate, the radiometric 1-D FPA receiver is moved into one direction by the linear scanner. From the experiment results, it is certain that MIRAE system can get enough good outdoor radiometer images to detect concealed metal weapons under clothing in the short range application such as security, comparing with other commercial and competitive passive imaging radiometer systems at W-band.

The radiometric resolution of a motion-induced synthetic aperture radiometer (MISAR) is analytically obtained from the standard deviation of a baseline response, an observation scenario, and the imaging method of the MISAR. The intrinsic long integration time given by the whole dwell time on moving platforms improves the radiometric resolution compared with the snapshot resolution of other nominal synthetic aperture radiometers. In addition, it is illustrated that the MISAR imaging holds the tradeoff relationship between the radiometric and spatial resolutions.

For the last few decades, microwave radiometers have played an important role in various remote sensing applications of the earth environment such as atmosphere, ocean and soil. Especially, various polarimetric emission for more accurate estimation. In general, the electromagnetic wave is represented as full Stoke parameters. The Stoke parameters can be defined as the horizontal and vertical polarization for the first and second parameters, and the 45 degree linear and circular polarization for the third and forth parameters, respectively. In this study, we developed the fully polarimetric radiometer to measure full Stokes parameter at 94GHz. For stable and high sensible Stokes parameters measurement, we implemented a wideband analog correlator and a total power type receiver with periodic calibration. In order to measure full Stokes parameters, it needs the calibration by using the additional polarized references. The fully polarimetric calibration standard is composed of a polarizing grid, a retardation plate, and reference sources. The characteristic of calibration standards was measured and evaluated.

The design method of calibration standard of fully polarimetric radiometer to measure the Stokes parameters at W-band is proposed. The information of 45° in a linear and a circular polarization are calibrated using the wire grid with thin Teflon substrate and the retardation plate which was implemented by dielectric plate with grove. The calibration standards show good performance on orthogonal channel polarization mixing (-17 to -25 dB), on mixing from the orthogonal channel into the polarimetric channels (-10.1 to -6.0 dB), and on mixing between polarization channels (-3.2 to -5.8 dB).

A 7.7mW/1.0ns/1.35V digital delay locked loop has been proposed in this paper. The dual-DLL architecture with racing operation is adopted to achieve low power operation and low jitter, which is primarily caused by the length of the delay line. The merged dual coarse delay line (MDCDL) is employed for low power and high frequency operation. This DLL utilizes an OR-AND DCC for wide duty cycle correction capability. The proposed DLL for DDR3 SDRAM is fabricated by a 54nm DRAM process technology. Experimental results show that ±10% duty error of external clock can be corrected in less than 400 cycles locking time with 1.0GHz operation frequency at 1.35V.

A 2-D Doppler-radiometer has been proposed to improve the poor angular resolution of microwave radiometers, using aperture synthesis on a moving platform. In this letter, we investigate drawbacks of the Doppler-radiometer, which have not been discussed previously in detail. The imaging method is revised to be suitable for imaging of distributed sources, which is the more common situation than a point source, and then the specklelike sidelobes in the point source response are discussed. In distributed source imaging, the specklelike sidelobes in the point source response of the Doppler-radiometer severely degrade the imaging performance, so it is necessary to reduce them. The cause of specklelike sidelobes is discussed, and a sparse array is proposed to improve the imaging performance of the Doppler-radiometer. The improvement is demonstrated by simulation of the point source response, showing reduced speckle.

Dual-channel Radiometers for Earth and Atmosphere Monitoring (DREAM) is the Korean spaceborne microwave radiometer. It is the main payload of Science and Technology SATlleite-2(STSAT-2) and will start the mission in December 2008. In this paper, we describe the radiometric calibration of DREAM. We also present the performance results of the system-level.

In this paper, we present the design and calibration of the fully polarimetric radiometer at 94 GHz. For stable and high sensible Stokes parameters measurements, we applied a wideband analog correlator and a total power type receiver with a periodic calibration. To perform the fully polarimetric calibration, a calibration standard was designed and tested. Using the calibration standard, the calibration gain-offset was estimated and evaluated. The measured sensitivities with the integration time of 10 ms are approximately 1.26 K and 1.27 K in the horizontal and vertical channels, respectively. Other performances of the developed system and the calibration are also described and discussed.

In this paper, high spatial resolution imaging of a motion induced synthetic aperture radiometer with sparse rectangular array is presented. The imaging process is described including an observation scenario and image formation. The equivalent array factor and instantaneous spatial frequency coverage are presented to demonstrate the performance. Additionally, the differences between the proposed system and previous studies are discussed.

The problem of estimating information symbols transmitted through non-Gaussian multipath CDMA wireless channels with a phased array is considered. First, a robust detector based on the minimax robust estimation theory is proposed. This proposed robust technique has a decreased sensitivity of the estimates with respect to an actually unknown distribution of random noises and interferences. Then, the estimation accuracy of information signals is analysed by Monte Carlo simulation of this direction-of-arrival estimation-based robust detector in multipath scenario.

The first Korean spaceborne microwave radiometer has been developed since 2004. Its name is the dual-channel radiometers for earth and atmosphere (DREAM). It is the main payload of the science and technology SATellite-2 that will be launched in 2008. Recently, the development and performance test of DREAM flight model (FM) was completed. This document presents the hardware specification and performance test results of DREAM FM.

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In this paper, new robust M-estimation techniques are developed for combating impulsive noise and multiple-access interference in communication systems. Power functions of the proposed robust estimators are obtained by minimizing a nonquadratic residual function derived from the Huber's minimax robust estimation theory. Maximum peaks of these power functions are used for estimation of communication signals as well as direction of arrival. A strong advantage of the proposed robust M-estimation algorithms is a decreased sensitivity of the estimates with respect to an actual unknown distribution of random noises and interferences. Simulation results demonstrate that the proposed robust algorithms, the robust median, and robust Huber estimators, offer significant performance gain over the conventional and minimum-variance distortionless-response estimators, with the best results given by the robust Huber estimator.

Dual-channel Radiometers for Earth and Atmosphere Monitoring (DREAM) is the Korean first spaceborne radiometer which is the main payload of Science and Technology SATellite-2 (STSAT-2). The satellite will be launched by Korea Space Launch Vehicle-1 (KSLV-1) at NARO Space Center in Korea in 2007. DREAM is a two-frequency, total power microwave radiometer with linear polarization. It measures the brightness temperature of the Earth at 23.8 and 37 GHz. In this paper, the characteristics and the preliminary design of DREAM are described.

This article evaluates the performance of interferometric synthetic aperture radiometer using sub-Y-type array proposed by our research group, SSL at GIST, Korea. The proposed array type has an improved resolution than the conventional Y-type known as optimal array configuration in the design of 2-D interferometric radiometer. To evaluate it, the interferometric synthetic aperture radiometer with 40 antenna array is developed at 37 GHz and two target noise sources were used for performance test. Through the experiments, the performance evaluation shows 23% improvement of angular resolution than the conventional Y-type

The monitoring techniques of red tide at present have been studied based on satellite remote sensing with optical and infrared band. In this article, a new approach to red tide monitoring at microwave and millimeter-wave frequency is proposed. To evaluate this idea, the dual frequency radiometer system with L- and W-band was implemented. The experiments were performed on a coastal area of southern sea in Korea to do in-situ test on August and September in 2003. The experiment results show that the red tide could be distinguished from clean seawater by the brightness temperature and detected using microwave radiometry

The sub-Y type configuration of antenna array is proposed to obtain a higher angular resolution than the case of Y-type array in this paper. The sub-Y type array consists of sub-arrays that are the four elements Y-type arrays. Using sub-Y-type array, one can obtain more wide visibility function than the case of conventional Y-type array keeping the hexagonal sampling characteristic. To analyze characteristics of the proposed configuration, the synthesized angular resolution is compared to resolution of Y-type with the same number of antennas through simulation. The temperature sensitivity of sub-Y type array is considered in view of the standard deviation of sampled visibility function. The performance evaluation by use of array factor simulation shows more than 40% improvement in average for angular resolution.

The proposed method is devised to reconstruct a focused radar image for a wide observation angle without an interpolation, and therefore, it improves the image quality and reduces the processing time. To evaluate the performance, it is compared with the conventional sampling method through simulation and experimental results. In the case of the proposed method, the computation time is improved more than 33% for the image size of 1024/spl times/1024 pixels.