• Title/Summary/Keyword: in-phase and quadrature

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A Study on the Equalization for Low Power Underwater Acoustic Communication (저전력 수중음향통신을 위한 등화기에 관한 연구)

  • Lee, Tae-Jin;Kim, Ki-Man
    • Journal of Navigation and Port Research
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    • v.36 no.3
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    • pp.169-173
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    • 2012
  • In this paper, we propose an equalizer to minimize the inter-symbol interference when PSSK(Phase Silence Shift Keying) technique is applied to the low power underwater acoustic communication. PSSK is a QPSK(Quadrature Phase Shift Keying) modulation combined with PPM(Pulse Position Modulation), and it was proposed for low power communication. However, it has poor performance due to delay spread of underwater channel. In this paper, we propose a decision feedback equalizer to minimize the error in PSSK receiver. The sea trial was performed to evaluate the performance of the proposed method. In the result, the BER of PSSK was $4.36{\times}10^{-2}$ before the equalizer was applied, but the BER of PSSK was $3.95{\times}10^{-4}$ after the proposed equalizer was applied.

Performance Evaluation of the Complex-Coefficient Adaptive Equalizer Using the Hilbert Transform

  • Park, Kyu-Chil;Yoon, Jong Rak
    • Journal of information and communication convergence engineering
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    • v.14 no.2
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    • pp.78-83
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    • 2016
  • In underwater acoustic communication, the transmitted signals are severely influenced by the reflections from both the sea surface and the sea bottom. As very large reflection signals from these boundaries cause an inter-symbol interference (ISI) effect, the communication quality worsens. A channel estimation-based equalizer is usually adopted to compensate for the reflected signals under the acoustic communication channel. In this study, a feed-forward equalizer (FFE) with the least mean squares (LMS) algorithm was applied to a quadrature phase-shift keying (QPSK) transmission system. Two different types of equalizers were adopted in the QPSK system, namely a real-coefficient equalizer and a complex-coefficient equalizer. The performance of the complex-coefficient equalizer was better than that of two real-coefficient equalizers. Therefore, a Hilbert transform was applied to the real-coefficient binary phase-shift keying (BPSK) system to obtain a complex-coefficient BPSK system. Consequently, we obtained better results than those of a real-coefficient equalizer.

The Analysis of Amplitude and Phase Image for Acoustic Microscope Using Quadrature Technique (쿼드러춰 방식에 의한 초음파현미경의 진폭과 위상영상 분석)

  • Kim, Hyun;Jun, Kye-Suk
    • The Journal of the Acoustical Society of Korea
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    • v.18 no.3
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    • pp.55-61
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    • 1999
  • In this study, we have constructed the acoustic microscope using quadrature technique and analyzed the relative variation of image intensity and the quality of image by reconstructing the amplitude and phase image for surface defects with tiny hight variation. In this experiment, we have constructed the scanning acoustic microscope using the focused transducer with 3㎒ center frequency and the quadrature detector. And we have fabricated aluminum samples with round defects whose depth is different and reconstructed the amplitude and phase images for the samples. One sample has round defects with 2㎜ diameter and 100㎛ depth and the other has round defects with 4㎜ diameter and 5㎜ depth. In the result of line scanning for the sample with 100㎛ round defects, it has been shown that the variation rate of amplitude image intensity is 7% and the variation rate of phase image intensity is 89%. The phase image has better contrast than amplitude image for the sample. In contrast to this, the amplitude image has better contrast than phase image for the sample with 5㎜ depth's defects. Accordingly there is big difference between amplitude image and phase image for depth variation of defects whose boundary is 1 wavelength. Consequently the acoustic microscope using quadrature detector can be evaluated efficiently more than using envelope detector, for detecting defects which have height variation less than 1 wavelength. And also the phase image and the amplitude image can be used for detecting defects of tiny height variation with complimentary relation.

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A Phase Stabilization System of EFPI for Damage Detection of Composite (복합재료 파손 검출을 위한 EFPI 센서 위상 안정화 시스템)

  • Kim,Dae-Hyeon;Gu,Bon-Yong;Bang,Hyeong-Jun;Kim,Cheon-Gon;Hong,Chang-Seon
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.31 no.8
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    • pp.44-49
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    • 2003
  • In case of an extrinsic Fabry-Perot interferometric sensor, the phase compensating technique is particularly necessary in applying the interferometer to detecting acoustic emission signals because of signal-fading problems. The technique makes it possible to maintain the phase at the quadrature point. In this paper, we developed the stabilization control sensor system that is composed of a broadband light source, a tunable Fabry-Perot (F-P) filter and a control-circuit board. A tension test of a composite specimen was performed to verify if the developed system could compensate the phase change induced from the tension strain and keep the phase at the quadrature point.

Effects of LDPC Code on the BER Performance of MPSK System with Imperfect Receiver Components over Rician Channels

  • Djordjevic, Goran T.;Djordjevic, Ivan B.;Ivanis, Predrag N.
    • ETRI Journal
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    • v.31 no.5
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    • pp.619-621
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    • 2009
  • In this letter, we study the influence of receiver imperfections on bit error rate (BER) degradations in detecting low-density parity-check coded multilevel phase-shift keying signals transmitted over a Rician fading channel. Based on the analytical system model which we previously developed using Monte Carlo simulations, we determine the BER degradations caused by the simultaneous influences of stochastic phase error, quadrature error, in-phase-quadrature mismatch, and the fading severity.

Comparison of phase noise characteristic of Quadrature Voltage Controlled Oscillator (직교신호 발생 전압제어 발진기의 위상 잡음 특성비교)

  • Cho, Il-Hyun;Lee, Moon-Que;Kim, Hyeong-Seok
    • Proceedings of the KIEE Conference
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    • 2005.07c
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    • pp.2333-2335
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    • 2005
  • Various CMOS quadrature-voltage-controlled oscillators(QVCOs) are designed and fabricated for the comparison of the phase noise. The core VCO is composed of two Colpitts oscillators which are cross-coupled with PMOS pair. For the comparison of phase noise with the proposed scheme, the conventional LC VCO followed by the frequency-divide-by-two is designed. The simulation result demonstrate that the proposed scheme shows better phase noise performance by 6dB than that of a conventional scheme in which LC VCO is followed by the frequency-divide-by-two.

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Blind symbol timing offset estimation for offset-QPSK modulated signals

  • Kumar, Sushant;Majhi, Sudhan
    • ETRI Journal
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    • v.42 no.3
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    • pp.324-332
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    • 2020
  • In this paper, a blind symbol timing offset (STO) estimation method is proposed for offset quadrature phase-shift keying (OQPSK) modulated signals, which also works for other linearly modulated signals (LMS) such as binary-PSK, QPSK, 𝜋/4-QPSK, and minimum-shift keying. There are various methods available for blind STO estimation of LMS; however, none work in the case of OQPSK modulated signals. The popular cyclic correlation method fails to estimate STO for OQPSK signals, as the offset present between the in-phase (I) and quadrature (Q) components causes the cyclic peak to disappear at the symbol rate frequency. In the proposed method, a set of close and approximate offsets is used to compensate the offset between the I and Q components of the received OQPSK signal. The STO in the time domain is represented as a phase in the cyclic frequency domain. The STO is therefore calculated by obtaining the phase of the cyclic peak at the symbol rate frequency. The method is validated through extensive theoretical study, simulation, and testbed implementation. The proposed estimation method exhibits robust performance in the presence of unknown carrier phase offset and frequency offset.

Design and Implementation of Microstrip Quadrature Coupler and High Power Transmitting/Receiving Switch Using Dynamic Loading Technique for 1-Tesal MRI System (동적 부하 기술을 이용한 1-Tesla 자기공명 영상 시스템용 마이크로 스트립 quadrature coupler 및 고출력 송수신 스위치의 설계 및 제작)

  • 류웅환;이미영;이흥규;이황수;김정호
    • Journal of the Korean Institute of Telematics and Electronics D
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    • v.36D no.3
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    • pp.1-11
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    • 1999
  • It is now common practice to utilize the quadrature RF coils to improve the signal-to-noise ratio (SNR) in the Magnetic Resonance Imaging (MRI) System. In addition, to make such an available SNR improvement, it is mandatory to use a well-designed quadrature coupler, which facilitates a perfect 3-dB coupling and quadrature-phase shift. However, the four ports matching condition has to be well considered during the RF excitation and the signal detection period. This work investigates the effects of such a mismatching condition (especially, due to patient) from the analysis, simulation, and real implementation and firstly proposes dynamic loading technique for a quadrature coupler and transmitting/receiving switch module to minimize a patient mismatching and enhance a system reliability. Also, we designed and implemented the quadrature coupler and transmitting/receiving switch module using microstrip. As a result, the SNR of our MRI system using the microstrip quadrature coupler and transmitting/receiving switch module with dynamic load increases 3 dB compared with the old one using USA quadrature switch. Also, the power capability of quadrature coupler and transmitting/receiving switch module is 5-kw peak power. Considering power loss and reduction of size, we used a RT/duroid 6010 substrate with high permittivity and for simulation we use Compact Software.

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Design of a 960MHz CMOS PLL Frequency Synthesizer with Quadrature LC VCO (960MHz Quadrature LC VCO를 이용한 CMOS PLL 주파수 합성기 설계)

  • Kim, Shin-Woong;Kim, Young-Sik
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.46 no.7
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    • pp.61-67
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    • 2009
  • This paper reports an Integer-N phase locked loop (PLL) frequency synthesizer which was implemented in a 250nm standard digital CMOS process for a UHF RFID wireless communication system. The main blocks of PLL have been designed including voltage controlled oscillator, phase frequency detector, and charge pump. The LC VCO has been used for a better noise property and low-power design. The source and drain juntions of PMOS transistors are used as the varactor diodes. The ADF4111 of Analog Device has been used for the external pre-scaler and N-divider to divide VCO frequency and a third order RC filter is designed for the loop filter. The measured results show that the RF output power is -13dBm with 50$\Omega$ load, the phase noise is -91.33dBc/Hz at 100KHz offset frequency, and the maximum lock-in time is less than 600us from 930MHz to 970MHz.

An Integer-N PLL Frequency Synthesizer Design for The 900MHz UHF RFID Application (900MHz UHF대역 RFID 응용을 위한 Integer-N PLL주파수 합성기 설계)

  • Kim, Sin-Woong;Kim, Young-Sik
    • The Journal of the Korea institute of electronic communication sciences
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    • v.4 no.4
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    • pp.247-252
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    • 2009
  • This paper presents an Integer-N phase-locked loop (PLL) frequency synthesizer using a novel prescaler based on a charge pump and clock triggering circuit. A quadrature VCO has been designed for the 900MHz UHF RFID application. In this circuit, a voltage-controlled oscillator(VCO), a novel Prescaler, phase frequency detector(PFD), charge pump(CP), and analog lock detector(ALD) have been integrated with 0.35-${\mu}m$CMOS process. The integer divider has been developed with a verilog-HDL module, and the PLL mixed mode simulation has been performed with Spectre-Verilog co-simulator. The sweep range of VCO is designed from 828 to 960 MHz and the VCO generates four phase quadrature signals. The simulation results show that the phase noise of VCO is -102dBc/Hz at 100 KHz offset frequency, and the maximum lock-in time is about 4us with 32MHz step change (from 896 to 928 MHz).

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