• Proceedings of the KSRS Conference
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• 2000.04a
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• pp.125-130
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• 2000

This paper deals with antenna configurations of a two-antenna synthetic aperture microwave radiometer for the high spatial resolution and precision of brightness temperature measurements. Four different types of antenna configurations are considered. The directional patterns of each type are compared in the paper.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 1998.10a
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• pp.180-182
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• 1998

• Proceedings of the Optical Society of Korea Conference
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• 2006.02a
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• pp.361-362
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• 2006

• Atmosphere
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• v.15 no.3
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• pp.167-178
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• 2005

Using the FSSP-100(FSSP) and Microwave Radiometer (MWR), the fog and clear day characteristics (the size and number concentration of fog particles and the liquid water content) have been measured and analyzed at Daegwallyoung observation site ($37^{\circ}41^{\prime}N$, $128^{\circ}45^{\prime}E$) during 27 - 30 November 2003 (fog day) and 19 January 2004 (clear day). During the fog days, the measured fog-particle size by using FSSP is 0.8~8.4 ${\mu}m$, which is similar to the WMO typical value, the fog number concentration varies from 121 to 200 count ($No./cm^2$) and the fog liquid water content from $0.018g/m^3-0.1g/m^3$ in the site. The precipitable water vapor obtained by the MWR, showing the correlation coefficient $R^2$=0.83 between the total precipitable water vapor obtained from the radio sonde and MWR, shows the larger amount (0.75-8.3 cm) during the fog days than the clear-sky data (0.2 cm).

• Journal of the Korean earth science society
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• v.33 no.3
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• pp.233-241
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• 2012

Based on the observation of the microwave radiometers at Cheongju, Hapcheon and Daegwallyeong in Korea, the precipitable water vapor and liquid water path have been analyzed for spatio-temporal characteristics. The observed datas have been validated by comparing precipitable water vapor between the microwave radiometer and the radiosonde near the sites. It resulted in the correlation coefficient of more than 0.8 in all three sites. For three regions, the precipitable water vapor shows similar seasonal variation and diurnal cycle, and that amount of precipitable water vapor increases from around 1000 LST and has a maximum value at 1900 LST. On the other hand, the liquid water path of microwave radiometer has regional differences for its seasonal variation, which seems to be caused by the geographical characteristics including the frequent fog and clouds in Daegwallyeong, a high mountain region (834 m from sea level), almost flat land in Chengju, and Sobaek Mountains in Hapcheon that blocks the westerly clouds.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.4
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• pp.266-269
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• 2018

A compact Q-band waveguide-to-microstrip transition for UAV(Unmanned Aerial Vehicle) radiometer applications is presented. The key features of this transition are simplicity, compactness, easy matching, and lower sensitivity to the dimensions and fabrication tolerances. The simple E-plane patch-type design is insensitive to the backshort cavity enclosure and misalignment between the waveguide and microstrip substrate. The primary parameters are optimized using a three-dimensional(3D) electromagnetic simulator(ANSYS HFSS). It exhibited better than 20-dB return loss at mid-band frequencies with less than 1-dB insertion loss for the back-to-back transition, and a return loss better than 15 dB over the frequency range of 36 GHz to 42 GHz.

• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.374-377
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• 2007

Dual-channel Radiometers for Earth and Atmosphere Monitoring (DREAM) was developed as the Korean first spaceborne microwave radiometer for earth remote sensing. It is the main payload of the Science and Technology SATellite-2 (STSAT-2). STSAT-2 will be launched by Korea Space Launch Vehic1e-l (KSLV-1) at NARO Space Center in Korea in 2008. The DREAM is a two-channel, total power microwave radiometers with the center frequencies of 23.8 GHz and 37 GHz. The bandwidths of radiometer are 600 MHz at 23.8 GHz and 1000 MHz at 37 GHz. The integration time is 200 ms and the required sensitivity is less than 0.5 K. In this paper, we summarize the specification and performance of the developed DREAM firstly. And we describe system integration and performance test of DREAM mounted on spacecraft.

• Korean Journal of Agricultural and Forest Meteorology
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• v.5 no.2
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• pp.128-137
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• 2003

Net radiation (Rn) is one of the most fundamental components in surface energy budget. For an accurate measurement of Rn, periodic and consistent calibrations of net radiometers are required. With a 4-month time interval, two field experiments were conducted to inter-compare and calibrate two types of net radiometers (the Q-7.1 and the CNR1), widely used in flux measurements. Differences between the Q-7.1 and the CNR1 net radiometers were within 7.7%, and the errors after calibration against the standard net radiometer were ＜3.2%. Radiometric responses and calibration factors appeared to have changed with sky renditions, especially temperature difference with season's progress. We concluded that the periodically calibrated Q-7.1 can replace more expensive, more accurate CNR1 net radiometer for long-term field measurements, providing that field calibrations of net radiometers are performed every 4-6 months interval.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.587-592
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• 2002

A new digital correlator fur an airborne synthetic aperture radiometer was designed in order to replace the conventional analog correlator unit which will become very complicated while the number of channels is increasing. The digital correlator uses digital IQ demodulator instead of the intermediate frequency (IF) phase shifter to make the correlation processing performed digitally at base band instead of analogly at IF. This technique has been applied to the digital receiver in softradio. The down-converted IF signals from each pair of receiver channels become low rate base-band digital signals after under-sampled, Digitally Down-Converted (DDC), decimated and filtered by FIR filters. The digital signals are further processed by two digital multipliers (complex correlation), the products are integrated by the integrators and finally the outputs from the integrators compose of the real part and the imaginary part of a sample of the visibility function. This design is tested by comparing the results from digital correlators and that from analog correlators. They are agreed with each other very well. Due to the fact that the digital correlators are realized with the help of Analog-Digital Converter (ADC) chips and the FPGA technology, the realized volume, mass, power consumption and complexity turned out to be greatly reduced compared with that of the analog correlators. Simulations show that the resolution of ADC has an influence on the synthesized antenna patterns, but this can be neglected if more than 2bit is used.

• Journal of Wetlands Research
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• v.18 no.2
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• pp.132-147
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• 2016

In this study the Microwave Imaging Radiometer using Aperture Synthesis (MIRAS) sensor onboard the Soil Moisture Ocean Salinity (SMOS) and Advanced Microwave Scanning Radiometer 2 (AMSR2) sensor onboard the Global Change Observation Mission-Water (GCOM-W1) based soil moisture retrievals were revised to obtain better accuracy of soil moisture and higher data acquisition rate over East Asia. These satellite-based soil moisture products are revised against a reference land model data set, called Global Land Data Assimilation System (GLDAS), using Cumulative Distribution Function (CDF) matching and regression approach. Since MIRAS sensor is perturbed by radio frequency interferences (RFI), the worst part of soil moisture retrieval, East Asia, constantly have been undergoing loss of data acquisition rate. To overcome this limitation, the threshold of RFI, DQX, and composite days were suggested to increase data acquisition rate while maintaining appropriate data quality through comparison of land surface model data set. The revised MIRAS and AMSR2 products were compared with in-situ soil moisture and land model data set. The results showed that the revising process increased correlation coefficient values of SMOS and AMSR2 averagely 27% 11% and decreased the root mean square deviation (RMSD) decreased 61% and 57% as compared to in-situ data set. In addition, when the revised products' correlation coefficient values are calculated with model data set, about 80% and 90% of pixels' correlation coefficients of SMOS and AMSR2 increased and all pixels' RMSD decreased. Through our CDF-based revising processes, we propose the way of mutual supplementation of MIRAS and AMSR2 soil moisture retrievals.