White noise

About: White noise is a research topic. Over the lifetime, 16496 publications have been published within this topic receiving 318633 citations.

Noise-predictive maximum likelihood (NPML) detection

Abstract: Sequence detectors for the digital magnetic recording channel that are based on noise-predictive partial-response equalization are described. Called Noise-Predictive Maximum Likelihood (NPML) detectors, they arise by imbedding a noise prediction/whitening process into the branch metric computation of a Viterbi detector. NPML detectors can be realized in a form that allows RAM table look-up implementation of the imbedded feedback. Alternatively, the noise prediction/whitening mechanism can be implemented as an infinite impulse response (IIR) filter. For a Lorentzian channel with operating points in the range 0.5

Noise generator using combined outputs of two pseudo-random sequence generators

Abstract: The pseudo-random-bit sequence generators are clocked by separate clock signals of different frequency. The two pseudo-random-bit sequence generator outputs are logically combined by an exclusive-or gate to provide a pseudo-random-bit sequence generator which, when converted to analog signal has improved white noise characteristics.

Adaptive time-varying cancellation of wideband interferences in spread-spectrum communications based on time-frequency distributions

Abstract: The paper proposes an adaptive method for suppressing wideband interferences in spread-spectrum (SS) communications. The proposed method is based on the time-frequency representation of the received signal from which the parameters of an adaptive time-varying interference excision filter are estimated. The approach is based on the generalized Wigner-Hough transform as an effective way to estimate the instantaneous frequency of parametric signals embedded in noise. The performance of the proposed approach is evaluated in the presence of linear and sinusoidal FM interferences plus white Gaussian noise in terms of the SNR improvement factor and bit error rate (BER).

Sensitivity Enhancement in Magnetic Resonance. I. Analysis of the Method of Time Averaging

Abstract: A theoretical analysis of the method of time averaging is made with special emphasis on the correlation effects caused by non‐white noise. It is shown that only in special cases is the signal‐to‐noise ratio improved exactly according to the square root of the number of successive scans through the investigated spectrum. This is shown in detail for random noise with an exponential‐cosine autocorrelation function. In the case of random noise with a pure exponential autocorrelation function, the deviation from the proportionality to the square root of the number of scans does not exceed a factor √2. If the frequency dependence of the power spectrum of the noise is given by |f|−λ, 0≤λ≤1, then the proportionality to the square root of the number of scans holds exactly. A peak in the noise power spectrum at a multiple of the repetition frequency of the scanning does affect the time averaging only if its width is smaller than the repetition frequency.