손민혁 Minhyuk Son , 윤영선 Youngsun Yun , 이병석 Byungseok Lee

DOI: JANT Vol.26(No.6) 373-379, 2022

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KASS (korea augmentation satellite system) is an SBAS (satellite based augmentation system) that must ensure the performance of aviation service in accordance with the International Civil Aviation Organization’s SARPs (standards and recommended practices) Annex 10 - Aeronautical Telecommunications. In order to guarantee the target service performance, the operating system must be operated, maintained and managed stably, and a maintenance system must be established for this purpose. From the maintenance point of view, the KASS subsystems were developed to consist of replacement units, and the maintenance organization and procedures to manage those subsystems and units were defined. In addition, the maintenance task for each the replacement unit was developed to ensure the availability performance required for the successful KASS operation, and the developed tasks were verified to sufficiently cover the activities to maintain the previously defined replacement units. The maintenance tasks developed through this study will be continuously verified in the actual operation preparation process prior to the full-scale provision of aviation services in the end of 2023, and will be updated accordingly.

안병선 Byeong-seon Ahn , 최성창 Sung-chang Choi , 황호연 Ho-yon Hwang

DOI: JANT Vol.26(No.6) 380-392, 2022

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In this paper, the new vertiport regulations of the FAA and EASA are analyzed for urban air mobility(UAM), and the major components of the vertipad and the new specifications of each component are analyzed, and UAM operation in various environments is analyzed. Additional components for vertiport and regulations for surrounding airspace were also reviewed. Afterwards, based on the size of the S-A1 aircraft being developed by Hyundai Motors, domestic vertiport specifications and layouts were investigated for UAM operation, and these were applied to the city of Incheon. In addition, the time required for using a taxi or car were compared with the time required for using UAM between major locations in Incheon and Seoul.

박재우 Jaewoo Park , 박건환 Geonhwan Park , 홍혜진 Hyejin Hong , 구성관 Sungkwan Ku

DOI: JANT Vol.26(No.6) 393-403, 2022

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Various studies suggest that the initial operating form of UAM, which is being presented as a solution to the urban traffic problem, will be similar to VTOL aircraft among current aircraft. In a form similar to determining the direction of the runway where fixed-wing aircraft take off and land, the vertiport where take-off and landing of VTOL aircraft takes place determines the flight direction of departure and arrival in consideration of the direction of the wind. Unlike areas where airports are generally built, in the case of downtown areas, it is expected that the characteristics of wind may continuously change depending on the environment of changing terrain or obstacles such as the construction of new buildings. In this study, long-term actual observation data for reviewing the take-off and landing directions at the city center where the location of the vertiport is expected are compared using a wind speed map, and the characteristics of the ground wind and the possibility of change in the direction of the predominant wind depending on the observation period and observation location confirmed.

김범수 Beomsoo Kim , 김정래 Jeongrae Kim , 부성춘 Sungchun Bu , 이철수 Chulsoo Lee

DOI: JANT Vol.26(No.6) 404-411, 2022

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The main function in operating the satellite navigation system is to accurately determine the orbit of the navigation satellite and transmit it as a navigation message. In this study, we developed software to determine the orbit of a navigation satellite by combining an extended Kalman filter and an accurate dynamic model. Global positioning system (GPS) and quasi-zenith satellite system (QZSS) orbit determination was performed using international gnss system (IGS) ground station observations and user range error (URE), a key performance indicator of the navigation system, was calculated by comparison with IGS precise ephemeris. When estimating the clock error mounted on the navigation satellite, the radial orbital error and the clock error have a high inverse correlation, which cancel each other out, and the standard deviations of the URE of GPS and QZSS are small namely 1.99 m and 3.47 m, respectively. Instead of estimating the clock error of the navigation satellite, the orbit was determined by replacing the clock error of the navigation message with a modeled value, and the regional correlation with URE and the effect of the ground station arrangement were analyzed.

김부겸 Bu-gyeom Kim , 기창돈 Changdon Kee

DOI: JANT Vol.26(No.6) 412-417, 2022

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In this paper, multi-GNSS network RTK MAC correction generation software developed based on MATLAB GUI is introduced. The software was developed as a post-processing software based on simulation data to evaluate the feasibility of an algorithm for generating correction for multi-GNSS including GPS, GLONASS, and Galileo. As a result of software operation, network RTK correction for each system of multi-GNSS is output in MATLAB file format. In this paper, to evaluate the performance of the developed software, the residual error was analyzed after applying the correction generated through the software to the user. As a result of the analysis, it was confirmed that effective network RTK correction could be generated by confirming that the residual errors of users were maintained at 10 cm or less.

임철순 Cheolsoon Lim , 조용래 Yongrae Jo , 이예빈 Yebin Lee , 차윤호 Yunho Cha , 박병운 Byungwoon Park , 박두경 Dookyung Park , 이승호 Seungho Lee

DOI: JANT Vol.26(No.6) 418-426, 2022

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Unlike OSR(observation space representation), the SSR(state space representation) augmentation system is suitable for a one-way broadcasting service because it provides the same corrections to all users in the service area. Due to this advantage, several GNSS(global navigation system) systems such as Galileo, BDS(beidou navigation satellite system), QZSS(quasi zenith satellite system) are establishing PPP (precise point positioning)/PPP-RTK precision positioning services based on SSR messages. Therefore, in this paper, we try to understand the trends of satellite-based PPP/PPP-RTK correction services by analyzing the system configurations, characteristics, and precise positioning performance of satellite-based SSR correction broadcasting services.

김혜지 Hyeji Kim , 강혁 Hyeok Kang , 이성봉 Seongbong Lee , 김형석 Hyeongseok Kim , 이동진 Dongjin Lee

DOI: JANT Vol.26(No.6) 427-433, 2022

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Obstacle detection, collision recognition, and avoidance technologies are required the collision avoidance technology for UAVs. In this paper, considering collinear multiple static obstacle, we propose an obstacle detection algorithm using LiDAR and a collision recognition and avoidance algorithm based on CPA. Preprocessing is performed to remove the ground from the LiDAR measurement data before obstacle detection. And we detect and classify obstacles in the preprocessed data using the K-means clustering algorithm. Also, we estimate the absolute positions of detected obstacles using relative navigation and correct the estimated positions using a low-pass filter. For collision avoidance with the detected multiple static obstacle, we use a collision recognition and avoidance algorithm based on CPA. Information of obstacles to be avoided is updated using distance between each obstacle, and collision recognition and avoidance are performed through the updated obstacles information. Finally, through obstacle location estimation, collision recognition, and collision avoidance result analysis in the Gazebo simulation environment, we verified that collision avoidance is performed successfully.

박건환 Geonhwan Park , 홍혜진 Hyejin Hong , 박재우 Jaewoo Park , 구성관 Sungkwan Ku

DOI: JANT Vol.26(No.6) 434-440, 2022

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The ICAO (International civil aviation organization)recommended the implementation of the GANP (global air navigation plan) for strategic decision-making and air traffic management evaluation. In this study, we proposed a new method for finding the route distance from KPI (key performance indicator) 05 actual route extension presented for air traffic management evaluation. For this purpose, we collected trajectory data for one month and calculated the en-route distances using the methods presented in ICAO and the methods presented by this author. In the ICAO method, the intersection point must be estimated through the equation of a circle for radius 40 NM and the equation of a straight line for an inner and outer point close to a circle in the track data, and four flight distances are calculated to calculate the en-route distance. In the method presented in this study, two flight distances are calculated without estimating the intersection point to calculate the en-route distance. To determine the error between the two methods, we used the performance evaluation index RMSE (root mean square error) and the determination factor R2 of the regression model.

김건희 Geon-hee Kim , 진미현 Mi-hyun Jin

DOI: JANT Vol.26(No.6) 441-447, 2022

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In this paper, we propose a FLL-assisted-PLL based time synchronization algorithm for telemetry systems where frequency and phase errors exist in time synchronization pulse. The telemetry system may analyze the flight state by acquiring the state information in the distributed system. Therefor, in order to collect each state information without errors, precise time synchronization between the master and the slave is required. At this time, the master’s time pulse have frequency and phase changes that can be caused by external and internal factors, so a method to maintain precision time synchronization is essential to provide telemetry data continuously. We propose the FLL-assisted-PLL based algorithm that is capable of high-speed synchronization and has high time synchronization accuracy. The proposed algorithm is verified through python simulation, and the VHDL Logic has been implemented in FPGA to check the performance according to the frequency errors and phase errors.

김정민 Jeong-min Kim , 엄송근 Song-geun Eom , 오정환 Jeong-hwan Oh , 이동진 Dong-jin Lee , 김도윤 Do-yoon Kim , 한상혁 Sang-hyuck Han

DOI: JANT Vol.26(No.6) 448-455, 2022

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In this study, when establishing a UTM(UAS Traffic Management) system, a corridor must be set to separate the flight distance between unmanned aerial vehicles, and the size of the corridor was calculated in consideration of TSE(Total System Error). The flight data of the straight section and the turning section were collected using a hybrid vertical take-off and landing unmanned aerial vehicle. The flight data were derived from the TSE using the SQSM(Scalar Quantity Summation Method) method, and the impact on the straight and turning sections was analyzed by calculating in detail by NSE(Navigation System Error) and FTE(Flight Technical Error). The corridor size was calculated by referring to the TSE analysis results and PBN (Performance-based Navigation) manual.

김영재 Young-jae Kim , 고상훈 Sang-hoon Koh , 박동현 Dong-hyun Park , 한석주 Seok-choo Han , 이대현 Dae-hyun Lee , 안정우 Jeong-woo An

DOI: JANT Vol.26(No.6) 456-463, 2022

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The SAM(Surface-to-Air Missile) systems will be operated until disposing of it after production, the necessary test and evaluation should be performed during the development stage to ensure the operational performance after deployment. As development of technologies related to the electromagnetic wave field of missile system is required, so the verification of the electromagnetic environment has become more important. Therefore it is necessary to carefully review whether there are any weaknesses through the analysis of the SAM system when establishing the test and evaluation procedure. This paper describes the general electromagnetic test procedure for SAM system and discusses the matters that need to be supplemented. Also, methods for supplementation and review results were written.

박상진 Sang-jin Park , 조영준 Yeong-jun Jo , 서동현 Dong-hyun Seo , 박인근 Lin-keun Park

DOI: JANT Vol.26(No.6) 464-473, 2022

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In this paper, about a lightweight design that satisfies the performance of UHF-GPS Antenna used in autonomous underwater vehicle is proposed. Structural analysis, watertight external pressure test and non-destructive testing used in the design process are decided in consideration of structural safety for operating external forces in the underwater environment. First, the material of radome is selected for the performance of the UHF-GPS Antenna for communication with the carrier on the underwater operation in consideration of the 20 bar pressure generated. And the material of radome as PA-GF is selected by conducting electromagnetic field analysis and structural analysis and by considering high strength, rigidity and high dielectric constant. Electromagnetic field analysis and structural analysis by the thickness of radome are additionally performed in order to satisfy the required weight of UHF-GPS antenna. After selecting the final model, its structural safety is verified through watertight external pressure test and non-destructive testing.

이성렬 Seong-real Lee

DOI: JANT Vol.26(No.6) 474-480, 2022

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Optical phase conjugation is one of techniques capable of compensating for distortion due to chromatic dispersion and nonlinearity, which are essential for long-distance transmission of wavelength division multiplexed (WDM) signal. We proposed and analyzed a way to solve the limitations of this technology through dispersion map with periodic dispersion profile. In the proposed system, optical phase conjugator (OPC) is placed at the position of 1:2 or 2:1 of the entire link, and the dispersion profile of dispersion map has periodic shape in the form of a sine wave or an inverse-sine wave. It was confirmed that the effective compensation of the distorted 960 Gb/s WDM signal was further improved through the proposed periodic dispersion map when the OPC was located at the 1:2 point instead of the 2:1 point of the entire link. In addition, it was found that the maximum RDPS allocated to fiber span should be 1,800 ps/nm or more in order to increase the design flexibility of dispersion-managed link with the proposed periodic dispersion map.

노재성 Jae-sung Roh

DOI: JANT Vol.26(No.6) 481-486, 2022

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The recent rapid growth of the IoT(Internet of Things) is leading to the spread of low-power wireless technology. A major challenge in designing IoT wireless networks is to achieve coexistence between different wireless technologies that share the 2.4 [GHz] ISM (Industrial Scientific Medical) frequency band. Therefore, there is a need for research on improving the reliability of wireless networks and coexisting operation between wireless networks. In particular, it is necessary to study an interference model and performance for mutual service coexistence in a BLE (Bluetooth Low Energy) wireless network environment, which is expected to be widely used as a connection medium between devices in various industrial fields. In this paper, the co-channel interference model with the IEEE 802.15.4 system is established focusing on the physical layer of the BLE system widely used in residential and industrial wireless applications, and the performance of the BLE wireless communication system is analyzed in the co-channel interference environment. As a result of the analysis, as the distance between the interference source and the BLE system increases in an environment where noise and co-channel interference exist, the amount of co-channel interference decreases and the error rate performance of the BLE system improves.

김지흥 Jeeheung Kim , 최현태 Hyuntae Choi , 이정수 Jungsu Lee , 장태성 Tae Seong Jang

DOI: JANT Vol.26(No.6) 487-495, 2022

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This paper describes the design and development of a high-power transmit receive module(TRM) for mounting on X-band synthetic aperture radar(SAR) of the NEXTSat-2. The TRM generates a high-power pulse signal with a bandwidth of 100 MHz in the target frequency range of X-band and amplifies a low-noise on the received signal. Tx. path of the TRM has output signal level of more than 200 watts (53.01 dB), pulse droop of 0.35 dB, signal strength change of 0.04 dB during transmission signal output, and phase change of 1.7 ˚. Rx. path has noise figure of 3.99 dB and gain of 37.38 ~ 37.46 dB. It was confirmed the TRM satisfies all requirements. The TRM mounted on the NEXTSat-2 flight model(FM) which will be launched using the KSLV-Ⅱ (Nuri).

주인웅 In-ung Ju , 강인숙 In-suk Kang , 김정연 Jeong-yeon Kim , 이성렬 Seong-real Lee , 최조천 Jo-cheon Choi

DOI: JANT Vol.26(No.6) 496-503, 2022

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In the reality that the fishing population is decreasing and the single-man fishing vessels is increasing, mandatory equipment for navigation and radio equipments for the safety of fishing boats has continued to be added. Therefore, many equipment such as navigation, communication and fishing are installed in the narrow steering room, so it is very confusing and a number of monitors are placed in the front, which is a factor that degrades the function of maritime observation. To solve this problem, we studied an interface that integrates and operates to major radio facilities such as very high frequency-digital selective calling equipment (VHF-DSC), automatic identification system (AIS) and fishing boat location transmission device (V-pass) into one multi function display (MFD) based on LAN. In addition, IEC61162-450 UDP packets and IEC61162 sentence were applied to exchange data through link between MFD and radio equipments, and additional messages needed for each equipment and function were defined. The integrated MFD monitor is easily operated by the menu method, and the performance of the interface was evaluated by checking the distress and emergency communication functions related to maritime safety and the message transmission status by equipment.

한형석 Hyung-seok Han

DOI: JANT Vol.26(No.6) 504-509, 2022

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In this paper, we deal with the stability condition of linear time-varying interval discrete systems with time-varying delays and unstructured uncertainty. For the time-varying interval discrete system which has interval matrix as its system matrices, time-varying delay time within some interval value and unstructured uncertainty which can include non-linearity and be expressed by only its magnitude, the stability condition is proposed. Compared with the previous result derived by using a upper bound solution of the Lyapunov equation, the new result is derived by the form of simple inequality based on Lyapunov stability condition and has the advantage of being more effective in checking stability. Furthermore, the proposed condition is very comprehensive, powerful and inclusive the previously published conditions of various linear discrete systems, and can be expressed by the terms of magnitudes of the time-varying delay time and uncertainty, and bounds of interval matrices. The superiority of the new condition is shown in the derivation, and the usefulness and advantage of the proposed condition are examined through numerical example.

여준호 Junho Yeo , 이종익 Jong-ig Lee

DOI: JANT Vol.26(No.6) 510-515, 2022

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In this paper, a microstrip patch sensor antenna (MPSA) for detecting the concentration of an ethanol-water solution in a microliter volume is proposed. A rectangular slot was added at the radiating edge of the patch to increase the sensitivity to the relative permittivity change. To improve a low input resistance caused by placing an ethanol-water solution, which is a polar liquid with high dielectric constant and high loss tangent, on the patch, a quarter-wave impedance transformer was added between the 50-ohm feedline and the patch, and the MPSA was fabricated on a 0.76 mm-thick RF-35 substrate. A cylindrical container was made of acryl, and 15 microliters of the ethanol-water solution was tested from 0% to 100% of ethanol concentration at 20% intervals. Experiment results show that the resonant frequency increased from 1.947 GHz to 2.509 GHz when the ethanol concentration of the ethanol-water solution was increased from 0% to 100%, demonstrating the performance as a concentration detecting sensor.

여준호 Junho Yeo , 이종익 Jong-ig Lee

DOI: JANT Vol.26(No.6) 516-521, 2022

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In this paper, a compact 4-bit chipless RFID(radio frequency identification) tag using a modified ELC(electric field-coupled inductive-capacitive) resonator and multiple slot resonators is proposed. The modified ELC resonator uses an interdigital-capacitor structure in the conventional ELC resonator to lower the resonance peak frequency of the RCS. The multiple slot resonators are designed by etching three slots with different lengths into an inverted U-shaped conductor. The resonant peak frequency of the RCS for the modified ELC resonator is 3.216 GHz, whereas those of the multiple slot resonators are set at 4.122 GHz, 4.64 GHz, and 5.304 GHz, respectively. The proposed compact four-bit tag is fabricated on an RF-301 substrate with dimensions of 50 mm×20 mm and a thickness of 0.8 mm. Experiment results show that the resonant peak frequencies of the fabricated four-bit chipless RFID tag are 3.285 GHz, 4.09 GHz, 4.63 GHz, and 5.31 GHz, respectively, which is similar to the simulation results with errors in the range between 0.78% and 2.16%.

박선배 Sun-bae Park , 유도식 Do-sik Yoo

DOI: JANT Vol.26(No.6) 522-527, 2022

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Object tracking is a field of signal processing that sequentially tracks the location of an object based on the previous-time location estimations and the present-time observation data. In this paper, we propose an adaptive scaling neural network that can track and adjust the scale of the input data with three recursive neural network (RNN) submodules. To evaluate object tracking performance, we compare the proposed system with the Kalman filter and the maximum likelihood object tracking scheme under an one-dimensional object movement model in which the object moves with piecewise constant acceleration. We show that the proposed scheme is generally better, in terms of root mean square error (RMSE) performance, than maximum likelihood scheme and Kalman filter and that the performance gaps grow with increased observation noise.

양성훈 Sung-hoon Yang , 최영 Young Choi , 정소영 So-young Jung , 안주현 Joo-hyun Ahn

DOI: JANT Vol.26(No.6) 528-535, 2022

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Although the domestic aviation industry has made rapid progress with the development of aircraft manufacturing and transportation technologies, aviation safety accidents continue to occur. The supervisory agency classifies hazards and risks based on risk-based aviation safety data, identifies safety trends for each air transportation operator, and conducts pre-inspections to prevent event and accidents. However, the human classification of data described in natural language format results in different results depending on knowledge, experience, and propensity, and it takes a considerable amount of time to understand and classify the meaning of the content. Therefore, in this journal, the fine-tuned KoBERT model was machine-learned over 5,000 data to predict the classification value of new data, showing 79.2% accuracy. In addition, some of the same result prediction and failed data for similar events were errors caused by human.