• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.10a
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• pp.355-356
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• 2018

An interferometer is antenna system composed fo two or more elements that can be used to determine the diretion of arrival (DOA) of a received signal by measuring the relative phase between receiving elements. In order to minimize the error of the direction-finding accuracy in interferometer direction-finding system (DFS), the phase correction is accomplished. In this paper, the several methods for the phase correction are classified and the advantage and disadvantage of those methods are compared.

• Journal of IKEEE
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• v.27 no.4
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• pp.636-643
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• 2023

In this paper, a high-speed calibration method for phased array antennas in the far-field is presented A max calibration, which is a simplification of the rotating-element electric-field vector (REV) method that calibrates each antenna element only through received power, and a method of grouping calibrations by sub-array unit rather than each antenna element were proposed. Using the Proximal Policy Optimization (PPO) algorithm, we found a partitioning optimized for the distribution of phased array antennas and calibrated it on a subarray basis. An adaptive max calibration method that allows faster calibration than the conventional method was proposed and verified through simulation. Not only is the gain of the phased array antenna higher while calibration is being made to the target, but the beam pattern is closer to the ideal beam pattern than the conventional method.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.21 no.5
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• pp.162-170
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• 2022

In this paper, the phased-array transceiver (TRX) channel amplitude and phase calibration method for a radar wind profiler (RWP) based on the 256 active phased array is discussed. Without the additional module, the TX and RX calibration paths were secured using couplers and switches in the TRX front ends and the TRX switching duplexers, and the amplitude and phase of the 256 TRX were calibrated using a gain and phase detector. The beam widths and side lobes of five beams (vertical, east, west, south, and north) of the calibrated 256 active phased array antenna were confirmed by a near-field which agreed well with the simulation results. The proposed calibration method can be easily applied to a system based on an active phased array operated in an outdoor environment.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.7
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• pp.18-23
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• 2000

An active phased away antenna consists of many channels including radiator and active circuitary that contains low noise amplifiers and phase shifters. Each channel has different initial phase shift and gain because of inequality in active circuitary itself, interface between radiator and active circuitary, beam forming network and other antenna configurations. This is an inherent problem in active phased away antenna, therefore each channels' initial phase shifts and gains should be calibrated for obtaining the designed radiation pattern and antenna gain. In this paper, an efficient calibration method for the active phased array antenna is presented. By performing the above method, thhe antenna gain is increased more than 2.0 dB after calibrating considerably unequal 12 channels' initial phase shifts and gains.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.3
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• pp.638-646
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• 2005

In recent wireless communications, direct conversion transceiver or If sampling SDR-based receivers have being designed as an alternative to conventional transceiver topologies. In direct conversion receiver a.chitectu.e, the 1.equency/phase offset between the RF input signal and the local oscillator signal is a major impairment factor even though the conventional AFC/APC compensates the service deterioration due to the offset. To rover the limited tracking range of the conventional method and effectively aid compensation scheme in terms of I/Q channel imbalances, the frequency/phase offset compensation in RF-front end signal stage is proposed in this paper. In RF-front end, the varying phase offset besides the fixed large frequency/phase offset are corrected by using early-late phase compensator. A more simple frequency and phase tacking function in digital signal processing stage of direct conversion receiver is effectively available by an ingenious frequency/phase offset tracking method in RF front-end stage.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.258-258
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• 2010

레이저 유기 형광법은 비침투적인 방법으로 플라즈마를 진단할 수 있는 장점이 있다. 특히 헬륨 플라즈마 내에서 전기장이 존재하는 경우에 헬륨의 에너지 준위가 분리되는 STARK 효과를 이용하여 기판 부근에 발생한 쉬스 내의 전기장을 측정할 수 있다[1]. 그러나 플라즈마의 생성을 위한 RF 소스와 레이저 간의 위상이 동기화 되지 않는 경우엔, 그 결과 값의 보정이 필요하다. 외부의 전기장이 시변하는 경우에 각각의 위상에서 헬륨의 여기종이 느끼는 전기장의 세기는 다르다. 따라서 레이저가 어떤 타이밍에 입사되는 가에 따라 신호의 분리되는 정도가 달라지는데, 레이저와 외부 전기장의 위상을 동기화하지 않은 경우에는 관측된 신호는 각각의 위상에서 여러 가지로 분리된 신호가 더해진 합의 형태로 나타난다. 이는 외부에서 인가된 전기장의 가장 큰 값을 나타낸다고 알려져 있었다[2]. 그러나 레이저 유도 형광 신호는 넓게 분산을 가지므로 이는 보정되어야 한다. 본 연구에서는 각각의 위상에서 출력되는 형광 신호를 구하고 시간의 영역에서 1주기 동안 적분하여 실제로 관측될 레이저 유도 형광신호의 보정치를 계산하였다. 이를 실험적으로 검증하기 위해서 유도 결합 플라즈마 반응 챔버 내에서 플라즈마를 방전시킨 후에, 레이저 유도 형광법을 사용하여 기판 위에 생성된 쉬스 내의 전기장을 측정하였다. 그리고, 랑뮤어 프루브를 이용하여 벌크 플라즈마 내의 플라즈마 전압을 구하고, 이를 적분 상수로 삼아 쉬스 내의 전위 분포를 구하였다. 또한 기판에 인가되는 전압을 직접 측정하여 위에서 구한 전위 분포치와 보정을 한 후의 전위 분포치를 비교, 검토하여 보정치를 검증하였다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.10
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• pp.27-33
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• 2004

In this paper, we present a carrier recovery circuit using the polarity-decision algorithm that recovers a phase and a frequency error simultaneously. The proposed algorithm catches a frequency error based on a differential of an angular velocity of the signal constellations. Using the differential of a phase error may compensate the frequency error. The symbol prediction method in the proposed algorithm accumulates the symbols, which makes easy to calculate a phase differential. The hardware size of the algerian is small since we use Q data or I only to get phase information. As a result, the algerian shows a pull-in range of normalized frequency error 0.5 under AWGN 15dB.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.11
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• pp.3023-3030
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• 2009

In this paper, a prediction and compensation method for the error in the phase measured by using the proportionality between two wavelengths in the TW-PMP (Two-wavelength Phase Measuring Profilometry) is proposed and experimental results are shown to verify the usefulness of the proposed method. For sample object, firstly, a phase-shifting with a quite large number of steps is adopted in measurement, compared with the conventional phase-shifting method, secondly, a 3-3 step phase-shifting method is used to measure the same object which is applied to high-speed 3D shape measurement, and then, measured results from these two phase-shifting methods are compared to calculate measurement noises. From the experimental results applying the proposed compensation method to the measured beat phase and absolute phase, it has proven that noises are decreased by 90% and 17.2% for each case.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.12C
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• pp.1029-1034
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• 2010

For All Digital QPSK receivers, a phase recovery scheme is required to fix the arbitrarily rotated I/Q quadrature signals due to the transmission path and clock mismatch between the transmitter and the receiver. The conventional Costas phase recovery loop scheme requires a separate AGC(Automatic Gain Control) to obtain the performance independent of input signal power. This paper proposes a simple scheme which separates the phase and amplitude of the input signal via CORDIC algorithm and performs the phase recovery and amplitude compensation simultaneously. The proposed scheme can considerably reduce the logic resources in hardware implementation, has been verified by C++ and Model Sim simulations.

• Korean Journal of Remote Sensing
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• v.31 no.2
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• pp.101-110
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• 2015

Synthetic Aperture Radar Interferometry (InSAR) is affected by various noise source such as atmospheric artifact, orbital error, processing noise etc.. Especially, one of the dominant noise source for long-wave SAR system, such as ALOS PALSAR (L-band SAR satellite) is the ionosphere effect because phase delays on radar pulse through the ionosphere are proportional to the radar wavelength. To avoid misinterpret of phase signal in the interferogram, it is necessary to detect and correct ionospheric errors. Recently, a MAI (Multipler Aperture SAR Interferometry) based ionospheric correction method has been proposed and considered one of the effective method to reduce phase errors by ionospheric effect. In this paper, we introduce the MAI-based method for ionospheric correction. Moreover we propose an efficient method that apply the method over non-coherent area using directional filter. Finally, we apply the proposed method to the ALOS PALSAR pairs, which include the west sea coast region in Korea. A polynomial fitting method, which is frequently adopted in InSAR processing, has been applied for the mitigation of phase distortion by the orbital error. However, the interferogram still has low frequency of Sin pattern along the azimuth direction. In contrast, after we applied the proposed method for ionospheric correction, the low frequency pattern is mitigated and the profile results has stable phase variation values within ${\pm}1rad$. Our results show that this method provides a promising way to correct orbital and ionospheric artifact and would be important technique to improve the accuracy and the availability for L-band or P-band systems.