• Journal of the Institute of Electronics Engineers of Korea SD
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• 제49권6호
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• pp.25-34
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• 2012

New calibration method for the near-field scanning (NFS) system is presented. The proposed calibration method consisted of a new near-field antenna (NFP) and newly devised patterns as circular patch patterns (CPPs) and meander patterns (MPs). The proposed patterns were used for improving spatial resolutions and simplifying a calibration procedure of the NFP compared to the conventional method defined in the IEC61967-3 and 6. Also, the effect of the length of NFPs on attenuation characteristics was investigated with length of 8mm and 30mm. For them, we designed and fabricated CPPs of diameter (D) = 20, 40, 60, and 100mm and MPs of various widths and spaces. We found the reverse relations between spatial resolutions and heights of measuring points by using simplified calibration procedure. The testing result shows that the spatial resolution of $120{\mu}m$ at height of $200{\mu}m$ was verified without complex correlation algorithms under 8GHz. For manufacturing cost all patterns and the NFP were realized with low-cost fabrication using PCB (FR-4) not by a conventional LTCC process. For verification of chip-level EMC from the results, near-field scanning system (NFSS) having step resolution of Sub-micron scale was produced and by using the proposed NFSS and proposed NFP measurement of chip shows accurately the shape of the resolution of $200{\mu}m$ patterns for securing a high level of chip-level EMC verification.

• Journal of Navigation and Port Research
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• 제41권4호
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• pp.189-194
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• 2017

The Moving Search Radar System (MSRS) monitors sea areas by moving along the coast. Since the radar is initially aligned to the front of the vehicle, it is important to know the changes in the heading azimuth of the vehicle to quickly acquire the target azimuth from the radar after the MSRS has moved. The heading azimuth can be obtained using the gyro compass, the GPS compass or the electronic compass. The electronic compass is suitable for MSRS requiring fast maneuverability due to its small volume, short stabilization time and low price. However, using a geomagnetic sensor may result in an error due to the surrounding magnetic field. Errors can make early automatic tracking of the satellites difficult and can reduce the radar detection accuracy. Therefore, this paper proposes a method to automatically compensate for the error reflecting the correction value on the radar obtained by comparing the reference azimuth calculated by solving the geodesic inverse problem using two coordinates between the radar and the geostationary satellite with the actually-directed azimuth angle of the satellite antenna. The feasibility and convenience of the proposed method were verified by applying it to the MSRS in the field.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제19권5호
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• pp.872-882
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• 1994

In this paper, the Low Noise Amplifier(LNA) is designed and fabricated to include a band pass filter characteristics considering the antenna system characteristics according to the transmitting and receiving signal level of communication satellite transponder. As an example, a 2-stage low noise amplifier and a 4-stage amplifier and designed, fabricated and measured at 14,0~14.5GHz of receiving frequency band. This fabricated LNA has shown the gain with very good flatness within pass-band, and its gain decreases rapidly out of band resulting in supperssion of the transmitting signal power leakage. It has shown the 20.3dB +- 0.1dB of pass-band gain, the 1.44dB +-0.04dB of noise figure and the 14dB rejection out of band(12.25~12.75GHz). The gain flatness, noise figure and group delay of this 2-stage LNA satisfactorily met the simulation results. And the fabricated 4-stage amplifier has shown the more than 42dB of pass-band gain, the +-0.25dB of flatness and the 28dB of the rejection effect for transmitting power leakage. The 2-stage LNA and 4-stage amplifier, in this paper, will bring a design margin for the input filter and also result in the system cost reduction.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• 제9권4호
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• pp.17-24
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• 2009

This paper deals with the cancellation performance of loop back interference signal in the case of multihop relay of 16-QAM received signal at the USN radio network. For this, it is necessary to the exchange of information with long distance located station by means of the relay function between the node in the USN environment. In the relay node, the loop-back interference signal which the retransmitting signal is feedback to the receiver side due to the antenna of transmitter and receiver are co-used or very colsely located or using the nonlinear device. Due to this signal, the performance of USN system are degraded which are using the limited resource of frequency and power. For improve this, it is necessary to applying the adaptive signal processing algorithm in order to cancellating the unwanted loop-back interference signal at the frontend of receiver in relaying node, we can get the better system and multi hop performance. In the adaptive signal processing, we considered the 16-QAM signal which has a good spectral efficiency, firstly, than, the QR-Array RLS algorithm was used that has a fairly good convergence property and the solving the finite length problem in the H/W implementation. Finaly, we confirmed that the good elimination performanc was confirmed by computer simulation in the learing cuved and received signal constellation compared to the conventional RLS.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제17권12호
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• pp.2806-2811
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• 2013

New technologies such as multi-antenna and small cell were proposed as key technology for the next generation mobile system to cope with the explosively increasing mobile data traffic. In particular, heterogeneous mobile communication network which can improve spatial reuse factor by exploiting macro and small cells simultaneously is attracting attention. However, the heterogeneous network has a problem that the utilization of small cells becomes low because the transmit power of macro base stations is much higher than that of small base stations and then the probability that mobile stations are attached to the macro base stations becomes high. This problem is dominant in uplink. The concept of cell range expansion bias to mitigate the problem was proposed by 3GPP and the corresponding standardization is in progress. In this paper, we analyze the downlink performance of the heterogeneous mobile communication network based on a system level simulator with the cell range expansion bias in terms of average cell spectral efficiency.

• Korean Journal of Remote Sensing
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• 제34권6_3호
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• pp.1415-1425
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• 2018

Kompsat-5 is the first Earth Observation Satellite which is equipped with an SAR in Korea. SAR images are generated by receiving signals reflected from an object by microwaves emitted from a SAR antenna. Because the wavelengths of microwaves are longer than the size of particles in the atmosphere, it can penetrate clouds and fog, and high-resolution images can be obtained without distinction between day and night. However, there is no color information in SAR images. To overcome these limitations of SAR images, colorization of SAR images using Cycle GAN, a deep learning model developed for domain translation, was conducted. Training of Cycle GAN is unstable due to the unsupervised learning based on unpaired dataset. Therefore, we proposed MS Cycle GAN applying multi-scale discriminator to solve the training instability of Cycle GAN and to improve the performance of colorization in this paper. To compare colorization performance of MS Cycle GAN and Cycle GAN, generated images by both models were compared qualitatively and quantitatively. Training Cycle GAN with multi-scale discriminator shows the losses of generators and discriminators are significantly reduced compared to the conventional Cycle GAN, and we identified that generated images by MS Cycle GAN are well-matched with the characteristics of regions such as leaves, rivers, and land.

• Korean Journal of Radiology
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• 제23권1호
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• pp.42-51
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• 2022

Objective: This study aimed to investigate the direction of tissue contraction after microwave ablation in ex vivo bovine liver models. Materials and Methods: Ablation procedures were conducted in a total of 90 sites in ex vivo bovine liver models, including the surface (n = 60) and parenchyma (n = 30), to examine the direction of contraction of the tissue in the peripheral and central regions from the microwave antenna. Three commercially available 2.45-GHz microwave systems (Emprint, Neuwave, and Surblate) were used. For surface ablation, the lengths of two overlapped square markers were measured after 2.5- and 5-minutes ablations (n = 10 ablations for each system for each ablation time). For parenchyma ablation, seven predetermined distances between the markers were measured on the cutting plane after 5- and 10-minutes ablations (n = 5 ablations for each system for each ablation time). The contraction in the radial and longitudinal directions and the sphericity index (SI) of the ablation zones were compared between the three systems using analysis of variance. Results: In the surface ablation experiment, the mean longitudinal contraction ratio and SI from a 5-minutes ablation using the Emprint, Neuwave, and Surblate systems were 28.92% and 1.04, 20.10% and 0.53, and 24.90% and 0.45, respectively (p < 0.001). A positive correlation between longitudinal contraction and SI was noted, and a similar radial contraction was observed. In the parenchyma ablation experiment, the mean longitudinal contraction ratio and SI from a 10-minutes ablation using the three pieces of equipment were 38.60% and 1.06, 32.45% and 0.61, and 28.50% and 0.50, respectively (p < 0.001). There was a significant difference in the longitudinal contraction properties, whereas there was no significant difference in the radial contraction properties. Conclusion: The degree of longitudinal contraction showed significant differences depending on the microwave ablation equipment, which may affect the SI of the ablation zone.

• Geophysics and Geophysical Exploration
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• 제8권4호
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• pp.262-269
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• 2005

Since the buried cultural relics are three-dimensional (3-D) objects in nature, 3-D survey is more preferable in archeological exploration. 3-D Ground Penetrating Radar (GPR) survey based on very dense data in principle, however, might need much higher cost and longer time of exploration than other geophysical methods commonly used for the archeological exploration, such as magnetic and electromagnetic methods. We developed a small-scale continuous data acquisition system which consists of two sets of GPR antennas and the precise positioning device tracking the moving-path of GPR antenna automatically and continuously. Since the high cost of field work may be partly attributed to establishing many profile lines, we adopted a concept of data acquisition at arbitrary locations not along the pre-established profile lines. Besides this hardware system, we also developed several software packages in order to effectively process and visualize the 3-D data obtained by the developed system and the data acquisition concept. Using the developed system, we performed 3-D GPR survey to investigate the possible historical remains of Baekje Kingdom at Buyeo city, South Korea, prior to the excavation. Owing to the newly devised system, we could obtain 3-D GPR data of this survey area having areal extent over about $17,000m^2$ within only six-hours field work. Although the GPR data were obtained at random locations not along the pre-established profile lines, we could obtain high-resolution 3-D images showing many distinctive anomalies, which could be interpreted as old agricultural lands, waterways, and artificial structures or remains. This cast: history led us to the conclusion that 3-D GPR method is very useful not only to examine a small anomalous area but also to investigate the wider region of the archeological interests.

• Journal of the Korean Institute of Gas
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• 제20권5호
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• pp.64-71
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• 2016

According to the urban gas business law, electrical corrosion prevention measures shall be installed to the buried gas pipelines and the pipe-to-soil potentials should be measured at the test box at least once a year. Most of the test boxes installed in urban area are usually located on the road where the vehicle travels, therefore, it is difficult to measure the CP potentials at the test boxes. That is, we need traffic control when carrying out the measurement of the CP potentials on daytime when the traffic is heavy, or we have to measure the potentials in the late night when the traffic is light. To solve these difficulties, we have studied remotely CP potential measuring method by using the patrol car. We have installed solid reference electrodes and data loggers under the test boxes on the site and received the CP potentials from the data loggers when the vehicle moves. It was difficult to send and receive the data because the data logger was located under the ground. We have applied 3 different method including 2 antenna systems to achieve best effective way in receiving the data. We have found the remote CP measuring method by using a car can save more 20 times of measuring time than conventional measuring methods.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• 제33권2호
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• pp.131-142
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• 2015

In order to support the development of a cost-effective river bathymetric system, this research has focused on modeling GPS observables, which are obtained by array of five single-frequency receivers (i.e., two references and three rovers) to estimate the high accurate kinematic position, and the surveying vessel altitude. Also, by applying all GPS measurements as multiple-baselines with constraining rover baselines, we derived the socalled ‘kinematic network model.’ From the model, the integer-constrained least-squares (LS) for position estimation and the implicit LS for attitude determination were implemented, while a series of simulation tests with respect to the baseline lengths around 2km performed to demonstrate its accuracy analysis. The on-the-fly (OTF) ambiguity resolution tests revealed that ninety-nine percents of time-to-fix-first ambiguity (TTFF) can be decided in less than two seconds, when the positioning accuracy of ambiguity-fixed solutions was assessed as the greater than or equal to one and two centimeters in horizontal and vertical, respectively. Comparing to the GPS-derived attitudes, the achievable accuracy gradually descended in sequence of yaw, pitch and roll due to the antenna geometric configuration. Furthermore, the RMSE values for the baseline lengths of three to six meters were within ±1′for yaw, and less than ±10′and ±20′for pitch and roll, respectively, but those of between six to fifteen meters were less than ±1′for yaw, ±5′for pitch, and ±10′for roll.