• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.20 no.2
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• pp.79-94
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• 2021

A GNSS receiver installed in autonomous vehicles is the most essential device for its navigation. However, if an intentional jamming signal is generated, there is a risk of exposure to an accident risk due to deterioration of the GNSS sensor's performance. Research is required to prevent this, and accordingly, a jamming generating device must be provided. However, according to the provisions of the law related to jamming, this is illegal. In this paper, we implement an in-vehicle jamming device that complies with the provisions of the law and does not affect the surrounding GNSS sensors. Driving simulation is used to evaluate the performance of the GNSS algorithm, and the malfunction of autonomous vehicles occurring in the interference environment and data errors output from the GNSS sensor are analyzed.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.6
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• pp.726-732
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• 2019

In this study, we proposed an asymmetric differential inductor to improve the linearity of differential power amplifiers. Considering the phase error between differential signals of the differential amplifier, the location of the center tap of the differential inductor was modified to minimize the error. As a result, the center tap was positioned asymmetrically inside the differential inductor. With the asymmetric differential inductor, the AM-to-AM and AM-to-PM distortions of the amplifier were suppressed. To confirm the feasibility of the inductor, we designed a 2.4 GHz differential CMOS PA for IEEE 802.11n WLAN applications with a 64-quadrature amplitude modulation (QAM), 9.6 dB peak-to-average power ratio (PAPR), and a bandwidth of 20 MHz. The designed power amplifier was fabricated using the 180-nm RF CMOS process. The measured maximum linear output power was 17 dBm, whereas EVM was 5%.

• Journal of Fisheries and Marine Sciences Education
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• v.3 no.2
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• pp.19-28
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• 1991

The United States has been developing a GPS(Global Positoning System), and now we can make use of it everywhere in the world. The author measured the usable time and took position fixes from three fixed stations in Japan in order to evaluate the positioning accuracy of GPS, firstly by the difference in the time of the year and, secondly by the difference in location between the stations in 1988. I was able to receive positioning signals from only 6 or 7 satellites, but in July 1991, 14 GPS satellites became available. The results obtained are summerized as follows: 1) The usable time was 7~9 hours from only 6~7 satellites. 2) In the case of the former, the time zone of position fixes varied with the time of the year and there were a little differences of the accuracy of position fixes except 3H(three dimensiomal high level positioning). In the case of the latter, there were not obvious locality differences in 3D(three dimensional positioning). But the positioning errors and number of data varied on each level in 2D(two dimensiomal positioning), although the positioning errors were smaller than 0.1 nautical mile. 3) Th standard deviations of Dep(departure) were larger than tat of D.lat(difference of latitude), and varied widely to the east and west. But the standard deviations were smaller than 100 meters.

• Journal of the Korean Vacuum Society
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• v.15 no.4
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• pp.331-337
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• 2006

Cavity-type beam position monitors were developed in collaboration with KEK to use for the future accelerators such as international linear collider (ILC) or x-ray free electron laser (XFEL) in PAL. BPM components such as BPM cavity, beam tubes, waveguides and feedthroughs were assembled by brazing at the same time to reduce mechanical errors during the fabrication. There are four screwed pins around outer rim of the cavity for the tuning of cavity frequency and x-y isolation. The resonance frequency of BPM is 6.422 GHz, the inner diameter of cavity is 53.822 mm, and the range of mechanical adjusting is $+ / - 250{\mu}m$. The x-y isolation was measured better than -40 dB after tuned. Test results of signal forms, x-y isolations, sensitivities are satisfied within requirements for the KEK ATF2 beam line.

• Journal of Advanced Navigation Technology
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• v.19 no.6
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• pp.499-506
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• 2015

Global navigation satellite systems (GNSS) is operating widely in civil and military area. GNSS signals, however, can be easily interfered because its signal is vulnerable to jamming. Thus, a sort of backup or alternative system is needed in order that the navigation performance is assured to a certain degree in case of GNSS jamming. In order to suggest a series of backup or alternative system of regional navigation, in this paper, we introduced a high altitude long endurance unmanned aerial vehicle (HALE UAV) with pseudolites using inverted GPS and transceiver system. We simulated the positioning error of the regional navigation system using HALE UAV with inverted GPS or transceivers concepts. We estimated the position error of HALE UAV calculate user position errors based on the position error of HALE UAV and general pseudorange error.

• Journal of Navigation and Port Research
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• v.36 no.10
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• pp.833-838
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• 2012

TDOA which is one of the position estimation methods is used on indoor positioning, jammer localization, rescue of life, etc. due to high accuracy and simple structure. This paper proposes the super-resolution TDOA estimator using MPM(Matrix Pencil Method). The proposed estimator has more accuracy and is applicable to narrowband signal compared with the conventional cross-correlation. Furthermore, its complexity is low because obtained data directly is used for construction of matrix unlike the MUSIC(Multiple Signal Classification) which is one of the well-known super-resolution estimator using covariance matrix. To validate the performance of proposed estimator, errors of estimation and computational burden is compared to MUSIC through software simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.7A
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• pp.733-742
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• 2008

In 3GPP LTE downlink system, initial cell search is essential for mobile station to connect to base station. In order to obtain information of the base station, the mobile station detects frame timing, frequency offset, and cell identification using primary synchronization channel(PSC) and secondary synchronization channel(SSC), which are defined in downlink OFDMA specification. In this paper, we analyze various detection algorithms in practical environment of inter-cell-interference, frequency offset, and multi-path fading channel and propose the optimal algorithm. Simulation results show that partial correlation method (for PSC acquisition) and interference cancellation method (for SSC detection) are the most superior algorithms among the applicable algorithms. Employ these two algorithms for receiver design, initial cell search is performed with 99% probability within 70ms in the channel environment considered.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.10
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• pp.1973-1980
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• 2017

In the case of a small UUV operating an active synthetic aperture sonar, various velocity disturbances may occur on the path due to the influence of external underwater environment, and this causes phase errors in coherent synthetic aperture processing, which has a large influence on the detected image. In this paper, when a periodic sinusoidal velocity disturbance is generated in the traveling direction, the phase generated by the round trip slope range at each position is estimated the cross correlation coefficient for multiple received signals and compensated the position variation in the overlapped DPC by the average value within the maximum allowable width. Through simulations, it has been confirmed that the images degraded by the velocity disturbance amplitude and fluctuating frequency of the UUV are removed from the false targets and the performance of azimuth resolution is improved by the proposed phase compensation method.

• Journal of the Korea Institute of Building Construction
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• v.10 no.3
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• pp.65-70
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• 2010

Steel frame construction in high places entails many risk factors. In order to improve the safety and productivity of steel frame construction, a project to develop a robotic tower-crane has been undertaken. As the first step, a real-time lifting-path tracking system is being developed. In a previous study, a laser-based tracking system was proposed. While a laser-based tracking system requires at least three laser sensors to detect the x, y, z coordinates of a lifted steel member, a GPS-based system has an advantage over the laser-based system, in that the x, y, z coordinates of a lifted steel member can be detected by a single GPS sensor. To improve the accuracy, arelative positioning method using two GPS sensors was proposed in a previous study. This paper reports an improved GPS-based lifting-path tracking system of a tower crane based on an integrated RF modem and GPS system. The results showedthat the RF modem could successfully send the identifier information to a server a maximum distance of 1 km away from the lifted steel beam, and the lifting path information of each beam captured by the GPS-based tracking system was successfully saved together. Also, byusing an improved algorithm for the GPS relative positioning method, the deviation was reduced to 0.61 m on average.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.7
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• pp.1413-1419
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• 2015

Monopulse RADAR is the radar which detects the range of the target using a single transmitted signal. In this paper, using 9.41GHz X-band radar, the research for the phase comparison monopulse algorithm used in the marine environment is conducted. In addition, by applying the phase comparison monopulse algorithm, we calculate the RMSE for the various antenna spacings and the positions of the target. Based on that result, we compare the performance of the phase comparison monopulse algorithm in the uniform linear array with that in the non-uniform linear array. Finally, the differences in performance among the MUSIC algorithm, Bartlett method and the proposed phase comparison monopulse algorithm are analyzed.