• Title/Summary/Keyword: Phase noise spectrum

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Spectral Estimation of the Pass-by Noise of an Acoustic Source (등속 이동 음원의 통과소음 스펙트럼 추정에 관한 연구)

  • Lim Byoung-Duk;Kim Deok-Ki
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.12 s.243
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    • pp.1597-1604
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    • 2005
  • The identification of a moving noise source is important in reducing the source power of the transport systems such as airplanes or high speed trains. However, the direct measurement using a microphone running with noise source is usually difficult due to wind noise, white the source motion distorts the frequency characteristics of the pass-by sound measured at a fixed point. In this study the relationship between the spectra of the source and the pass-by sound signal is analyzed for an acoustic source moving at a constant velocity. Spectrum of the sound signal measured at a fixed point has an integral relationship with the source spectrum. Nevertheless direct conversion of the measured spectrum to the source spectrum is ill-posed due to the singularity of the integral kernel. Alternatively a differential equation approach is proposed, where the source characteristics can be recovered by solving a differential equation relating the source signal to the distorted measurement in time domain. The parameters such as the source speed and the time origin, required beforehand, are also determined only from the frequency-phase relationship using an auxiliary measurement. With the help of the regularization method, the source signal is successfully recovered. The effects of the parameter errors to the estimated frequency characteristics of the source are investigated through numerical simulations.

Analytical Proof of Conservation of Power in the LTV Phase Noise Theory for Noisy Oscillators (선형시변 발진기 위상잡음 이론의 전력 보존성의 증명)

  • Jeon, Man-Young
    • The Journal of the Korea institute of electronic communication sciences
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    • v.7 no.4
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    • pp.855-859
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    • 2012
  • This study derives a generalized PSD formula in the LTV phase noise theory for noisy oscillators. The derived formula analytically proves that the LTV phase noise theory can predict the conservation of the power in the noisy oscillation signals. Additionally, the derived formula allows the theory to account for the behavior of the power spectrum over the entire frequency range including the regions around higher harmonics as well as fundamental frequency.

A Study on Analysis of Phase Noise Effects in a FM-CW Radar System (FM-CW 레이다 시스템에서의 위상잡음 영향 분석에 관한 연구)

  • Lee, Jong-Gil
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.15 no.9
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    • pp.1840-1846
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    • 2011
  • It is necessary to estimate the Doppler spectrum for each range cell for the extraction of useful information from the return echoes in radar systems used for the remote sensing purpose such as detection of moving targets and weather surveillance. The signal amplitude in the beat frequency band is the important parameter in the detection and tracking of targets. However, strong clutter echoes do exist in most radar operation environments and the system phase noise spreads both the clutter and signal echoes of the target. In this paper, the effects of this system phase noise are analyzed concerning the clutter and the signal beat spectrum. It is shown that the separation capability of adjacent beat signal depends on the degree of spread in the clutter and beat signal caused by the radar system phase noise

A Comparative Study on the Power Spectrum of Three-Phase and Two-Phase RCD-PWM Scheme with Fixed Switching Frequency (고정 스위칭 주파수를 갖는 3상 및 2상 RCD-PWM의 파워 스펙트럼 비교)

  • Kim J.G.;Jung Y.G.;Lim Y.C.;Yang H.Y.;Wi S.O.
    • Proceedings of the KIPE Conference
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    • 2003.07a
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    • pp.308-312
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    • 2003
  • The objective of this paper is to investigate the power spectrum of a three-phase and a two-phase RCD (Random Pulse Centered Displacement) PWM scheme. The two-phase or three-phase pulses of RCD-PWM scheme are mutually center-aligned as in SVM(Space Vector Modulation), but the common pulse center is displaced randomly from the middle of the period. To verify the validity of the proposed two-phase RCD-PWM scheme, the power spectra of the output voltage, the d.c link current in the inverter drives and the radiated acoustic noise are experimentally investigated. And, the performance of the proposed two-phase RCD-PWM scheme was compared and discussed with the conventional three-phase RCD-PWM scheme.

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Numerical analysis on the low noise designs of Savonius wind turbines by using phase difference in vortex shedding (와류이탈 위상차를 이용한 사보니우스형 풍력터빈의 소음 저감 설계에 관한 수치적 연구)

  • Kim, Sanghyeon;Cheong, Cheolung
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2013.04a
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    • pp.166-171
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    • 2013
  • In this study, low noise designs of a Savonius wind turbines are numerically investigated. From a previous study, it was found that the high harmonic components whose fundamental frequency is higher than the BPF were found to be dominant in noise spectrum of a Savonius wind turbine. On a basis of this observation, S-shaped blade tip is proposed as a low design factors that decrease wind turbine noise by inducing phase differences in vortex shedding. The conventional Savonius and S-shaped turbines are investigated using Hybrid CAA method where flow field around the turbine are computed using CFD techniques and the radiated noise are predicted by applying acoustic analogy to the computed flow data. Noise reductions by these design factors are confirmed by comparing the predicted noise levels from these turbines.

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Influences and Compensation of Phase Noise and IQ Imbalance in Multiband DFT-S OFDM System for the Spectrum Aggregation (스펙트럼 집성을 위한 멀티 밴드 DFT-S OFDM 시스템에서 직교 불균형과 위상 잡음의 영향 분석 및 보상)

  • Ryu, Sang-Burm;Ryu, Heung-Gyoon;Choi, Jin-Kyu;Kim, Jin-Up
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.21 no.11
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    • pp.1275-1284
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    • 2010
  • 100 MHz bandwidth and 1 Gbit/s data speed are needed in LTE-advanced for the next generation mobile communication system. Therefore, spectrum aggregation method has been studied recently to extend usable frequency bands. Also bandwidth utilization is increased since vacant frequencies are used to communicate. However, transceiver structure requires the digital RF and SDR. Therefore, frequency synthesizer and PA must operate over wide-bandwidth and RF impairments also increases in transceiver. Uplink of LTE advanced uses DFT-S OFDM using plural power amplifier. The effect of ICI increases in frequency domain of receiver due to phase noise and IQ imbalance. In this paper, we analyze influences of ICI in frequency domain of receiver considering phase noise and IQ imbalance in multiband system. Also, we separate phase noise and IQ imbalance effect from channel response in frequency domain of uplink system. And we propose a method to estimate the channel exactly and to compensate IQ imbalance and phase noise. Simulation result shows that the proposed method achieves the 2 dB performance gain of BER=$10^{-4}$.

Improvement of Phase Noise in Frequency Synthesizer with Dual PLL (이중 PLL 구조 주파수 합성기의 위상 잡음 개선)

  • Kim, Jung-Hoon;Park, Beom-Jun;Kim, Jee-Heung;Lee, Kyu-Song
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.25 no.9
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    • pp.903-911
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    • 2014
  • This paper proposes a high speed frequency synthesizer with dual phase-locked loop(PLL) structure to improve phase noise level and shape in a wideband receiver. To reduce phase noise and fractional spur, a output frequency of $1^{st}$ PLL used as reference frequency of $2^{nd}$ PLL is changed. The frequency synthesizer has been designed with 1 Hz frequency resolution using digital NCO in 6.5~8.5 GHz wide spectrum. The measured results of the fabricated frequency synthesizer show that the output power is about -3 dBm, the maximum lock-in time and phase noise are within 60 us and -95 dBc/Hz at 10 kHz offset, respectively.

Synchronization Scheme Using Phase Offsets of PN Sequences (PN 부호의 위상오프셋을 이용한 동기 방법)

  • Song, Young-Joon;Han, Young-Yearl
    • Proceedings of the Korea Electromagnetic Engineering Society Conference
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    • 2003.11a
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    • pp.581-584
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    • 2003
  • It is important to know phase offsets of PN (Pseudo Noise) sequences in spread spectrum communications since the acquisition is equivalent to make a phase offset between a receiving PN sequence and a PN sequence of local PN generator be identical. In this paper, a phase offset enumeration method for PN sequences with error detection, and its application to the synchronization are proposed. The phase offset enumeration far an n-tuple PN sequence and its error detection are performed when one period of the sequence is received. Once the phase offset of the receiving sequence is calculated, we can easily accomplish the synchronization by initializing shift registers of a local PN generator according to the phase offset value. The mean acquisition time of the proposed synchronization method is derived analytically, and we see that the method acquires very fast acquisition in the high SNR (Signal-to- Noise Ratio) environment.

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