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386 results on '"Park, Seong Ook"'

1. Dynamic Geometry-Based Stochastic Channel Modeling for Polarized MIMO Systems with Moving Scatterers

Author

Radpour, Hamed, Minz, Laxmikant, Park, Seong-Ook, Kim, Duck-Yong, and Moon, Young-Chan

Subjects
Electrical Engineering and Systems Science - Systems and Control, Electrical Engineering and Systems Science - Signal Processing
Abstract

This paper introduces a four-dimensional (4D) geometry-based stochastic model (GBSM) for polarized multiple-input multiple-output (MIMO) systems with moving scatterers. We propose a novel motion path model with high degrees of freedom based on the Brownian Motion (BM) random process for randomly moving scatterers. This model is capable of analyzing the effect of both deterministically and randomly moving scatterers on channel properties. The mixture of Von Mises Fisher (VMF) distribution is considered for scatterers resulting in a more general and practical model. The proposed motion path model is applied to the clusters of scatterers with the mixture of VMF distribution, and a closed form formula for calculating space time correlation function (STCF) is achieved, allowing the study of the behavior of channel correlation and channel capacity in the time domain with the presence of stationary and moving scatterers. To obtain numerical results for channel capacity, we employed Monte Carlo simulation method for channel realization purpose. The impact of moving scatterers on the performance of polarized MIMO systems is evaluated using 2 by 2 MIMO configurations with various dual polarizations, i.e. V/V, V/H, and slanted 45{\deg} polarizations for different signal-to-noise (SNR) regimes. The proposed motion path model can be applied to study various dynamic systems with moving objects. The presented process and achieved formula are general and can be applied to polarized MIMO systems with any arbitrary number of antennas and polarizations., Comment: 10 pages, 10 Figures

Published
2023

2. Internal Calibration Process Using Chirp Pulses with Application of the Adam Learning Algorithm

Author

Kweon, Junho, Jung, Chan-Yong, Bae, Kyung-Bin, and Park, Seong-Ook

Subjects
Electrical Engineering and Systems Science - Signal Processing
Abstract

We propose a new internal calibration process using chirp pulses. Our method is utilized to mitigate thermal drift, which is unwanted changes and usually occurs in active elements such as a high power amplifier and low noise amplifier. The proposed method has advantages from two distinct aspects: calibration signal and algorithm. In respect to the calibration signal, our method does not contain an additional signal source because chirp pulses, which are normally used for remote sensing, are used as calibration signals. Moreover, our methods solve the ambiguity problem of analyzing a phase shift which occurs when sinusoidal signals are used as calibration signals. In regards to the algorithm, the Adam learning algorithm avoids learning in the wrong direction, unlike the conventional gradient descent. Using our method, mathematical forms of received signals are acquired successfully. Our method shows better effectivity compared to the conventional gradient descent algorithm. After compensation, the maximum differences of gain and phase become 0.06 dB and 2.42 degrees, respectively., Comment: This work has been submitted to the IEEE for possible publication

Published
2020

3. FMCW SAR with New Synthesis Method Based on A-SPC Technique

Author

Park, Junhyeong, Jung, Dae-Hwan, and Park, Seong-Ook

Subjects
Electrical Engineering and Systems Science - Signal Processing, Electrical Engineering and Systems Science - Image and Video Processing
Abstract

Frequency modulated continuous wave (FMCW) radar is emerging as a trendy radar system for synthetic aperture radar (SAR). This letter proposes a novel method for the extraction of the SAR image with the FMCW radar. The proposed method can improve the quality of the SAR image. For the verification, we built an automobile SAR (AutoSAR) system and conducted experiments to extract the SAR map by using the AutoSAR system. Then, we synthesized SAR images through both the conventional method and the proposed method to demonstrate the performance of the proposed method. The experimental results show that the SAR image has been successfully improved by the proposed method., Comment: 4 pages, 4 figures

Published
2020

4. Small Drone Classification with Light CNN and New Micro-Doppler Signature Extraction Method Based on A-SPC Technique

Author

Park, Junhyeong, Park, Jun-Sung, and Park, Seong-Ook

Subjects
Electrical Engineering and Systems Science - Signal Processing, Electrical Engineering and Systems Science - Image and Video Processing
Abstract

As the threats of small drones increase, not only the detection but also the classification of small drones has become important. Many recent studies have applied an approach to utilize the micro-Doppler signature (MDS) for the small drone classification by using frequency modulated continuous wave (FMCW) radars. In this letter, we propose a novel method to extract the MDS images of the small drones with the FMCW radar. Moreover, we propose a light convolutional neural network (CNN) whose structure is straightforward, and the number of parameters is quite small for fast classification. The proposed method contributes to increasing the classification accuracy by improving the quality of MDS images. We classified the small drones with the MDS images extracted by the conventional method and the proposed method through the proposed CNN. The experimental results showed that the total classification accuracy was increased by 10.00 % due to the proposed method. The total classification accuracy was recorded at 97.14 % with the proposed MDS extraction method and the proposed light CNN., Comment: 5 pages, 8 figures, 3 tables

Published
2020
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5. Advanced Stationary Point Concentration Technique for Leakage Mitigation and Small Drone Detection with FMCW Radar

Author

Park, Junhyeong, Park, Jun-Sung, Bae, Kyung-Bin, and Park, Seong-Ook

Subjects
Electrical Engineering and Systems Science - Signal Processing
Abstract

As the threats of small drones have grown, developing radars to detect the small drones has become an important issue. In earlier studies, we proposed the stationary point concentration (SPC) technique for the small drone detection with frequency-modulated continuous-wave (FMCW) radar. The SPC technique is a new approach to mitigate the leakage that is an inherent problem in the FMCW radar. The SPC technique improves the signal-to-noise ratio of the small drones by reducing the noise floor and provides accurate distance and velocity information of the small drones. However, the SPC technique has shortcomings in realizing it. In this paper, we present the drawbacks of the SPC technique clearly and propose an advanced SPC (A-SPC) technique. The A-SPC technique can overcome the drawbacks of the SPC technique while taking all the good effects of the SPC technique. The experimental results verify the proposed A-SPC technique and show its robustness and usefulness., Comment: This work has been submitted to the IEEE for possible publication

Published
2020
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6. Leakage Mitigation in Heterodyne FMCW Radar For Small Drone Detection with Stationary Point Concentration Technique

Author

Park, Junhyeong, Park, Seungwoon, Kim, Do-Hoon, and Park, Seong-Ook

Subjects
Electrical Engineering and Systems Science - Signal Processing
Abstract

Recently, as the drones have become smaller and smarter, they are emerging as new threats to the military and the public. To prevent the threats, the development of the radar to detect the small drones is needed. The frequency modulated continuous wave (FMCW) radar is one of the radar types for the drone detection. The heterodyne architecture for the FMCW radar is often applied to resolve the dc offset problem. However, the leakage from a transmitter into a receiver, the notorious problem of the FMCW radar, is still a challenging problem. Especially, the phase noise of the leakage increases the noise floor and deteriorates the signal to noise ratio. In order to mitigate this problem, in this paper, the stationary point concentration technique is proposed. Without additional hardware, the proposed technique can be implemented through frequency planning and digital signal processing. The results show that the proposed technique significantly lowers the noise floor over the desired range domain., Comment: This work has been submitted to the IEEE for possible publication. arXiv admin note: text overlap with arXiv:1807.06324

Published
2018
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7. A Novel Channel Sounding Method Based on Pulsed LFM Signal for mm-Wave Application: Instrumentation, Measurement, and Analysis

Author

Bae, Kyung-Bin, Yoo, Youngin, Park, Seungwoon, and Park, Seong-Ook

Abstract

Recently, there has been increasing demand to exploit a wider spectrum in higher frequency bands to improve the performance of new wireless communication devices and systems for millimeter-wave (mm-Wave) communications and fifth-generation (5G) mobile networks. Channel measurement and modeling are crucial for the design and development of such 5G devices and systems. In general, among various channel sounding methods, the most appropriate method has been selectively used depending on the channel characteristics to be measured. In this article, we propose an advanced sounding technique based on linear frequency modulation (LFM) pulse signal to strengthen channel sounding capabilities fitting well in higher frequency bands. The unique property of the LFM signal, where the instant frequency change corresponds to the sweep time, ensures that the output of the proposed channel sounder is proportional to the scattering parameter. Using this, we present an extended capability of the proposed sounding technique to measure channel characteristics such as delay spread, Doppler spread (DS), and Rician-K factor of small-scale fading channels emulated in a reverberation chamber (RC).

Published
2025
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8. Liquid-Crystal-Based Beam-Steering Guided-Wave Metasurface Antenna at Millimeter-Wave Band

Author

Park, Jinki, Yoo, Youngin, Lee, Changjae, Yoon, Dong Ki, and Park, Seong-Ook

Abstract

In this letter, we present the design and fabrication of a liquid crystal (LC)-based metasurface antenna for millimeter-wave beam-steering applications. Unlike the conventional beamforming systems that rely on phase shifters, our approach harnesses the electrical tunability of LCs. We target a frequency of 34.5 GHz, taking advantage of the pronounced low dielectric loss characteristics exhibited by LCs. The proposed antenna uses a substrate-integrated waveguide (SIW) to feed millimeter-wave to metasurface unit cells, and each cell's radiation is controlled through dc voltage biasing of the. The measurement results demonstrate a beam-steering range of 120° with a maximum gain of 10.754 dBi and a sidelobe level (SLL) of −11.562 dBc at the boresight.

Published
2024
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9. Miniaturized 24 GHz FMCW Radar Leakage Mitigation With Synchronized Subtraction

Author

Kim, Han-Sol, Meang, Jiyeol, Kim, Ju-Hye, Ko, Dong-Sik, Seo, Seong-Ho, Azim, Muhammad Tayyab, and Park, Seong-Ook

Abstract

Frequency-modulated continuous-wave (FMCW) radar sensors are widely used to measure range, velocity, and target status. As the range of applications for FMCW radar sensors expands, there is an increasing demand for smaller FMCW radar sensors suitable for use in confined spaces. To reduce the form factor of the FMCW radar sensor, the distance between the transmit (Tx) and receive (Rx) antennas is also reduced. This decrease in antenna separation increases the magnitude of the leakage signal transmitted from the Tx to the Rx antenna. However, the leakage signal makes it difficult for the FMCW radar sensor to detect the target by increasing the noise floor. In this article, we present an advanced method to mitigate the increased leakage signal power in the miniaturized FMCW radar sensor. We have fabricated a miniaturized homodyne FMCW radar with consistent leakage signal characteristics. We also propose a method to minimize the influence of the leakage signal by storing the leakage signal characteristics and using the stored data when operating the radar. The experimental results show significant leakage signal power reduction. This technique not only preserves the power of the received target signals but also improves the overall performance of compact FMCW radar sensors. The proposed method provides a basis for miniaturized radar sensors to contribute to various industries by providing an effective solution to the leakage signal problem of small radar technology.

Published
2024
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14. Ultralow‐Voltage Frequency Tunning of Liquid Crystal‐Based GHz Antenna via Nanoscratching Method.

Author

Lee, Changjae, Park, Jinki, Chi, Ye‐Eun, Yoo, Youngin, Park, Seong‐Ook, and Yoon, Dong Ki

Subjects
ANTENNAS (Electronics), METALLIC surfaces, HIGH voltages, LIQUID crystal films, LIQUIDS, HIGH temperatures, LIQUID crystals, NEMATIC liquid crystals, SUBSTRATE integrated waveguides
Abstract

Liquid crystal (LC)‐based radio‐frequency (RF) tunable antennas garner attention because of their compact size and minimal heat generation. Exploiting the LC's property to alter the RF permittivity depending on its alignment, voltage‐induced orientational switching enables frequency modulation of the radiated wave. To ensure dependable antenna performance, precise control of the initial LC alignment is crucial, which is conventionally achieved by polyimide (PI) coating followed by the rubbing process (PI‐rubbing). However, this approach demands high temperature (200 °C) and prolonged processing time (2 h), while also necessitating high voltage for LC reorientation due to induced excessive surface polar anchoring strength. Here, a PI‐free‐nanoscratching method creating 1D channels is introduced that induces initial LC alignment in a desired direction. The initial orienting capability of the scratched metal surface is superior to that of the PI‐rubbed surface. Furthermore, the LC‐based antenna employing the nanoscratching method shows a remarkable resonance frequency shift of up to 3 GHz with a low voltage of 2 V. This driving voltage is five times lower than that of antennas using the conventional PI‐rubbing method, which can open a new era for the next generation LC‐antenna. [ABSTRACT FROM AUTHOR]

Published
2024
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19. Clock Offsets in TDOA Localization

Author

Seong, Nak-Seon, Park, Seong-Ook, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Dough, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Youn, Hee Yong, editor, Kim, Minkoo, editor, and Morikawa, Hiroyuki, editor

Published
2006
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23. Multichannel Along-Track Interferometric SAR System Implementation Using FMCW Radar.

Author

Kang, Young-Geun, Park, Seungwoon, Kim, Eunsung, Kim, Kyeongrok, and Park, Seong-Ook

Abstract

Along-track synthetic aperture radar interferometry (ATI) systems are used to detect a moving target and to estimate its radial velocity. A dual-channel (single-baseline) ATI system estimates the velocity ambiguously because there are many candidate velocities corresponding to the interferometric phase. To resolve the ambiguity of the estimates, a multichannel (multibaseline) ATI system is required. This letter proposes an efficient implementation technique of a multichannel ATI system by using a frequency-modulated continuous wave (FMCW) radar and an antenna arrangement method considering the inherent bi-static characteristic of FMCW radars. Also, a simple and robust radial velocity estimation algorithm suitable for the proposed system model is presented. The validity of the algorithm is confirmed with simulated ATI results. [ABSTRACT FROM AUTHOR]

Published
2023
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25. Commercial Fixed-Wing Drone Redirection System Using GNSS Deception

Author

Chae, Myoung-Ho, Park, Seong-Ook, Choi, Seung-Ho, and Choi, Chae-Taek

Abstract

As drones become more common today, the threat of reconnaissance or attack drones to core facilities has increased, and countermeasures against them have become essential. In this study, a drone redirection system was proposed to counter the illegal intrusion of commercial fixed-wing drones. The drone redirection system was designed as a closed-loop system that automatically redirects the drone to a target position. The main novelty of this study is a proposed system that can automatically redirect a commercial fixed-wing drone, which has not been previously explored. We proposed two strategies for redirecting drones. Additionally, simple drone modeling with a path-following algorithm was used to easily model various drones. The drone model was then tuned using flight test data, and the results were compared. Simulations were performed on the designed drone redirection system model to verify the performance of the two proposed strategies for redirecting drones in conjunction with drone fail detection and innovation check. The performance of the drone redirection system was assessed through flight tests of Remo-M and simulations of MicroPilot's Hardware-in-the-Loop Simulator (HWILS). Through simple drone modeling, drone flight tests, and the test results from HWILS, it was proved that the drone redirection system can be applied to various fixed-wing drones.

Published
2023
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36. Cassegrain antenna with hybrid beam steering scheme for mobile satellite communications

Author

Jung, Young-Bae, Shishlov, Alexander V., and Park, Seong-Ook

Subjects
Satellite communications -- Equipment and supplies, Antennas (Electronics) -- Design and construction, Satellite communications, Business, Computers, Electronics, Electronics and electrical industries
Abstract

A hybrid antenna (HA) with a modified beam steering method is proposed. This antenna has a Cassegrain structure composed of two reflectors and a feeder. The parabolic-shaped main reflector is designed for high gain, while the subreflector is rotational and flat. The feeder is a phased array with arbitrary shaped aperture and 20 element antennas. The HA is capable of two-dimensional beam steering by means of two operations: rotation of the subreflector and phase control of the feed array. The subreflector is small in size and weight, so it can provide rapid beam scanning. Designed to be loaded in vehicles, the HA and can communicate with satellites on the move by tracking the beam control of the feed array. A prototype of the HA is fabricated with aluminum using a machining center operated by computerized numerical control. The prototype is operated at Ka-band for TX and K-band for RX with gains of 47 dBi and 44.4 dBi, respectively, at a steering angle of 0% The two-dimensional beam steering within [+ or -] 2[degrees] with respect to 45[degrees] elevation is realized by the subreflector and feed array. All radiation patterns in the beam steering zone meet ITU-R s.465-5 regulations. Index Terms--Hybrid, mobile antenna, reflector, satellite communications.

Published
2009

37. Ka-band shaped reflector hybrid antenna illuminated by microstrip-fed horn array

Author

Jung, Young-Bae and Park, Seong-Ook

Subjects
Antennas (Electronics) -- Design and construction, Antennas (Electronics) -- Optical properties, Optics, Geometrical, Optics, Physical, Business, Computers, Electronics, Electronics and electrical industries
Abstract

The numerical simulation and experimental results of a shaped reflector hybrid antenna (SRHA) structure are presented. The SRHA design was optimized for a scan range of [+ or -]3[degrees] for a broadside of 45[degrees] in elevation to maintain a gain of more than 38 dBi and low side-lobes. The designed SRHA has an aperture size of less than 60 x 70 [cm.sup.2] and an offset structure fora Iow profile to meet the need for a mobile satellite platform. The antenna geometry and reflector surface was determined by a geometrical optic (GO) method and the radiation pattern was obtained by physical optic (PO) analysis. A microstrip horn array was used as a feeder and was composed of eight elements. The number of array elements was chosen so as to maximize antenna performances, such as gain and efficiency, without overdesign. The SRHA breadboard, including a shaped reflector and a feed horn array, was fabricated and measured. The measured results showed good agreement with the simulation and met the performance required of SRHA. Index Terms--Hybrid antenna, satellite communications, shaped-reflector.

Published
2008

38. Hepta-band internal antenna for personal communication handsets

Author

Bhatti, Rashid Ahmad and Park, Seong Ook

Subjects
Antennas (Electronics) -- Design and construction, Cellular telephones -- Equipment and supplies, Wireless telephone, Wireless voice/data device, Business, Computers, Electronics, Electronics and electrical industries
Abstract

Modern personal communication handsets are shrinking in size and are required to operate at multiple frequency bands for enhanced functionality and performance. This poses an important challenge for antenna designers to build multiband antennas within the limited allowable space. In this paper, an internal antenna covering seven frequency bands is presented for personal communication handsets. The proposed antenna operates at GSM (880-960 MHz), DCS (1710-1880 MHz), PCS (1880-1990 MHz), UMTS (1900-2170 MHz), WiBro (2300-2390 MHz), Bluetooth (2.4-2.48 GHz), and WLAN (5.0-5.5 GHz) frequency bands. Measured input return loss of the antenna is better than -10 dB at all the frequency bands with reasonable radiation performance. Antenna volume is 30 mm x 15 mm x 4.0 mm (1.8 [cm.sup.3]) that makes it attractive for modern multiband and multifunctional slim handsets. Index Terms--Handset antenna, internal antennas, multiband, planar inverted-F antenna (PIFA), slim antenna.

Published
2007

39. Analysis of the small band-rejected antenna with the parasitic strip for UW

Author

Kim, Ki-Hak and Park, Seong-Ook

Subjects
Antennas (Electronics) -- Design and construction, Ultra wideband technology -- Usage, Strip transmission lines -- Design and construction, Business, Computers, Electronics, Electronics and electrical industries
Abstract

A novel band-rejected ultrawideband antenna with one parasitic strip is presented in this paper. It is designed to work on a substrate FR4 that has a thickness of 1 mm and relative permittivity of 4.6, and to operate from 3 to 17 GHz. The proposed antenna is fed by microstrip line and utilizes the parasitic strip to reject the frequency band (5.15-5.825 GHz) limited by IEEE 802.11a and HIPERLAN/2. The size of the antenna is 20 x 20 [mm.sup.2] and this antenna has good radiation characteristics. Effects of varying the location and length of the parasitic strip and the structure of the ground and monopole patch on the antenna performance have also been studied. Index Terms--Microstrip line, parasitic strip, ultrawideband (UWB).

Published
2006

40. A miniature UWB planar monopole antenna with 5-GHz band-rejection filter and the time-domain characteristics

Author

Cho, Young Jun, Kim, Ki Hak, Choi, Dong Hyuk, Lee, Seung Sik, and Park, Seong-Ook

Subjects
Ultra wideband technology -- Research, Antennas (Electronics) -- Design and construction, Time-domain analysis, Business, Computers, Electronics, Electronics and electrical industries
Abstract

A planar monopole antenna with a staircase shape and small volume (25 x 26 x 1 [mm.sup.3]) is proposed in this paper. With the use of a half-bowtie radiating element, the staircase-shape, and a modified ground plane structure, the proposed antenna has a very wide impedance bandwidth measured at about 11.6 GHz (2.9-14.5 GHz, bandwidth ratio about 1:5) below VSWR 2 including the WLAN band notched in the vicinity of 5 GHz. An omnidirectional radiation pattern is obtained. The group delay which is an indication of linearity between two proposed antennas is less than 1 ns. The electrical characteristics in terms of frequency and time domains and physical ones of the proposed antenna make it attractive for use in ultrawideband (UWB) systems. Index Terms--Group delay, short pulse characteristics, time domain characteristics, ultrawideband (UWB), ultrawideband (UWB) antenna.

Published
2006

44. An ultrawide-band double discone antenna with the tapered cylindrical wires

Author

Kim, Ki-Hak, Kim, Jin-U, and Park, Seong-Ook

Subjects
Antennas (Electronics) -- Research, Business, Computers, Electronics, Electronics and electrical industries
Abstract

A novel double diseone antenna is composed of the asymmetric biconicaL antenna and upside-down discone antenna. The asymmetric biconical antenna has all-wire structure like octopus legs for covering at lower operating frequency, and the upside-down discone antenna has conical shape playing a role as covering at higher operating frequency. An elaborate assembly of two antenna exhibits a 1:100 impedance bandwidth (180 MHz-18 GHz) with VSWR below 2.5 while maintaining an acceptable omnidirectional radiation pattern except at about 12 GHz region. The simulated performances of the proposed antenna are verified by the measured results of the fabricated antenna. There seems to be good agreement with each other. These features make such antennas highly suitable for application to UWB system. Index Terms--Asymmetric biconical antenna, double discone antenna.

Published
2005

45. A triple-band internal antenna: design and performance in presence of the handset case, battery, and human head

Author

Sim Dong-Uk and Park, Seong-Ook

Subjects
Antennas (Electronics) -- Research, Wireless telecommunications equipment -- Research, Wireless telecommunications equipment, Business, Computers, Electronics, Electronics and electrical industries
Abstract

An internal triple-band antenna fed by a microstrip line is proposed for operating at PCS, IMT-2000, and Bluetooth bands. As a starting point, a two-branch meander-line antenna is used to achieve the desired resonant frequency. A broadband characteristic for each band can be optimized by tuning the parts of radiating meander lines and size of each strip line segment. Considering normal use situation, the initially designed structure of the proposed antenna is extended and modified to tune the desired frequency bandwidth on the placement of handset case and battery, and in the presence of the head. Detailed model of the handset case is implemented to check the effects of the phone case and battery on the antenna performance. The return loss and radiation patterns from the proposed antenna built in a phone case in the presence of the phantom head are presented. It is found that the battery and human head have a strong influence on the antenna input impedance, radiation patterns, and gain for the internal antenna configurations. The computational values are presented to validate the experimental results. Index Terms--Handsets, human head, internal antennas, phantom, triple-band antennas.

Published
2005

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