• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.2 no.3
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• pp.10-16
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• 1991

The error networks due to the measuring systems and the test fixture must be previously calibrated in order to characterize the microwave devices. In this paper, it is presented a new method to characterize the error networks in which only two different microstrip lines are used for the calibration. Once each length of two calibrat- ing microstrip lines is accurately defined, the calibrated data can be easily obtained without acknowledgement for the propagation constant. The end effect is not considered when fabricated the microstrip lines used to calibration. The ATF13736 GaAs MESFET is characterized by means of the calibrating procedure with this method. The range of measuring frequency is 2 to 18 GHz, and the bias voltage and current are $V_{DS}$ =2.5V, $I_{DS}$ =20mA, respectively. Compared the calibrated data with data sheet, it is showed that the magnitude is nearly agreed with each other and the phase is deviated by 0.1 to 12 degrees in lower frequencies.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.2C
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• pp.306-314
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• 2004

Some receiver(and most transmit) beamforming algorithms with an array antenna at a cellular CDMA base stations require accurate internal and external calibrations. The external calibration, which usually needs to be done only once, determines the array manifolds, i.e. the complex response of each antenna as a function of DOA(Directions of Arrival). The internal calibrations are necessary because characteristics of RF/IF circuity of each receiver chain vary differently in response to temperature or humidity changes. We propose an iterative subspace-based calibration algorithm for an asynchronous CDMA-based antenna away in the presence of unknown gain and phase error is presented. We verify the subspace-based calibration algorithms by performing the experiment using measured data. Also, we propose an efficient algorithm using the simulated annealing technique. This algorithm overcomes the problem of the initial guessing in the subspace-based approach.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.1
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• pp.137-144
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• 2013

A delay-locked loop (DLL) that generates a 32-phase clock with the operating frequency of 125 MHz is introduced. The proposed DLL uses a delay line of $4{\times}8$ matrix architecture to improve a differential non-linearity (DNL) of the delay line. Furthermore, a integral non-linearity (INL) of the proposed DLL is improved by calibrating phases of clocks that is supplied to four points of an input stage of the $4{\times}8$ matrix delay line. The proposed DLL is fabricated by using $0.11-{\mu}m$ CMOS process with a 1.2 V supply. The measured operating frequency range of the implemented DLL is 40 MHz to 280 MHz. At the operating frequency of 125MHz, the measurement results shows that the DNL and INL are +0.14/-0.496 LSB and +0.46/-0.404 LSB, respectively. The measured peak-to-peak jitter of the output clock is 30 ps when the peak-to-peak jitter of the input clock is 12.9 ps. The area and power consumption of the implemented DLL are $480{\times}550{\mu}m^2$ and 9.6 mW, respectively.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.47 no.3
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• pp.81-86
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• 2010

Since CORDIC (COordinate Rotation DIgital Computer) is able to carry out the phase operation, such as vector to phase conversion or rotation of vectors, with adders and shifters, it is well suited for the design of the frequency synchronization unit in OFDM receivers. It is not easy, however, to fully utilize the CORDIC in the OFDM demodulator because of the non-linear characteristics of the direction sequence (DS), which is the representation of the phase in CORDIC. In this paper a new representation method is proposed to linearize the direction sequence approximately. The maximum phase error of the linearized binary direction sequence (LBDS) is also discussed. For the purpose of designing the hardware, the architectures for the binary DS (BDS) to LBDS converter and the LBDS to BDS inverse converter are illustrated. Adopting LBDS, the overall frequency synchronization hardware for OFDM receivers can be implemented fully utilizing CORDIC and general arithmetic operators, such as adders and multipliers, for the phase estimation, loop filtering of the frequency offset, derotation for the frequency offset correction. An example of the design of 22 bit LBDS for the T-DMB demodulator is also presented.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.1
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• pp.97-103
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• 2018

In satellite communication, modulated beacon signal is spreaded by gold sequence and the modulated beacon is transmitted via linear phase modulation. Due to the difference in characteristics of the satellite and the receiver on the ground, frequency offset (FO) occurs. An existing modulated beacon receiver is a method of synchronizing the frequency of a modulated beacon signal using FFT(Fast Fourier Transform), which not only increases the delay and complexity in terms of system implementation but also has a separate circuit for compensating the phase difference due to FO and phase offset from FFT points. In order to overcome this problem, this paper proposes and analyzes a scheme for compensating and demodulating the coarse FO and phase offset at one time using the 2-phase shaped characteristics of the modulated beacon signal. Also, through the simulation, the modulation index suitable for the proposed method is analyzed and the appropriate cumulative number is also analyzed.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.1
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• pp.110-116
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• 2016

This paper describes 1.2-V 5-Gb/s scalable low voltage signaling(SLVS) differential transmitter(TX) with a digital impedance calibration and equalizer. The proposed transmitter consists of a phase-locked loop(PLL) with 4-phase output clock, a 4-to-1 serializer, a regulator, an output driver, and an equalizer driver for improvement of the signal integrity. A pseudo random bit sequence generator is implemented for a built-in self-test. The proposed SLVS transmitter provides the output differential swing level from 80mV to 500mV. The proposed SLVS transmitter is implemented by using a 65-nm CMOS with a 1.2-V supply. The measured peak-to-peak time jitter of the implemented SLVS TX is about 46.67 ps at the data rate of 5Gb/s. Its power consumption is 1.88 mW/Gb/s.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.2
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• pp.143-148
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• 2013

This paper study about multi-beam for ditection of arrival estimation in wireless system. estimate a direction of arrival of target in multi input-output array antennas system. Beam steering method are divided by beam steering method of elevation angle or beam forming method, stack beam steering, frequency steering, phase steering radar and digital beam forming radar. Proposed algorithm is combined SVD method and antenna weight error compensation method with phase and amplitude compensation to effectivity beam steering. Through simulation, we were analysis of performance that general algorithm and proposed target estimation algorithm in this paper. It was proved to improved proposal algorithm than general algorithm in target direction of arrival estimation.

• 한국지형공간정보학회:학술대회논문집
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• 2002.03a
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• pp.150-155
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• 2002

SAR 시스템은 능동적 센서로 마이크로파라 불리우는 전자기파를 직접 지상에 보내고 돌아오는 신호의 위상과 진폭을 이용하여 영상으로 나타내는 간섭성 시스템이다. 이러한 영상의 특성으로 인해 날씨나 태양의 유 무에 상관없이 영상을 취득할 수 있는 장점이 있다. 또한, 최근에는 기존의 다중분광 위성영상과의 SAR 영상의 Data Fusion을 통해 지상의 새로운 정성적 정보를 취득하려는 시도 등 나날이 그 활용성이 증대되고 있는 상황이다. 그러나 SAR 영상의 광범위한 활용을 위해서는 먼저 영상의 지형보정이 선행되어야 한다. 따라서 본 연구에서는 SAR 영상의 활용을 위해서 선행되어야 할 지형보정의 알고리즘을 컴포넌트 기반의 프로그램으로 구현하고 대상연구지역에 대한 적용을 통해 그 활용성과 가능성을 보여주고자 한다. 연구대상지역은 ERS-1, ERS-2 SAR로 촬영된 대전광역시와 그 주변지역으로 해당 SAR 영상에 대하여 엄밀지형보정 알고리즘과 경사거리 영상을 지상거리 영상으로 변환하는 알고리즘을 개발하여 적용하였다. 실험결과 공칭해상도 30m의 ERS 영상에 대하여 39.7m(X방향으로 24.5m, Y방향으로 31.3m)의 수평오차를 나타내었으며 경사거리 영상의 지상거리 영상으로의 변환도 원활하게 수행됨을 알 수 있었다. 마지막으로 본 연구를 통해 연구된 모든 알고리즘은 컴포넌트 기반으로 설계하고 구현되어 향후 국내 SAR 처리기술 개발에 있어서 공유할 수 있도록 하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.4
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• pp.71-79
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• 1992

In general, the accelerogram of earthquake ground motion or the accelerogram obtained from dynamic tests contain various errors. In these errors of the accelerograms, there are instrumental errors(magnitude and phase distortion) due to the response characteristics of accelerometer and the digitizing error concentrated in low and high frequency components and random errors. Then, these errors may be detrimental to the results of data processing and dynamic analysis. An efficient method which can correct the errors of the accelerogram is proposed in this study. The correction of errors can be accomplished through four steps as followes ; 1) using an interpolation method a data form appropriate to the error correction is prepared, 2) low and high frequency errors of the accelerogram are removed by band-pass filter between prescribed frequency limits, 3) instrumental errors are corrected using dynamic equilibrium equation of the accelerometer, 4) velocity and displacement are obtained by integrating corrected accelerogram. Presently, infinite impulse response(IIR) filter and finite impulse response (FIR) filter are generally used as band-pass filter. In the proposed error correction procedure, the deficiencies of FIR filter and IIR filter are reduced and, using the properties of the differentiation and the integration of Fourier transform, the accuracy of instrument correction and integration is improved.

• Journal of Advanced Navigation Technology
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• v.8 no.1
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• pp.26-37
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• 2004

Consistent and realistic error covariance information is important for position estimation, error analysis, fault detection, and integer ambiguity resolution for differential GNSS. In designing a position domain carrier-smoothed-code filter where incremental carrier phases are used for time-propagation, formulation of consistent error covariance information is not easy due to being bounded and temporal correlation of propagation noises. To provide consistent and correct error covariance information, this paper proposes two recursive filter algorithms based on carrier-smoothed-code techniques: (a) the stepwise optimal position projection filter and (b) the stepwise unbiased position projection filter. A Monte-Carlo simulation result shows that the proposed filter algorithms actually generate consistent error covariance information and the neglection of carrier phase noise induces optimistic error covariance information. It is also shown that the stepwise unbiased position projection filter is attractive since its performance is good and its computational burden is moderate.