Pseudo-random Noise Signal Research Articles

Attractors of a randomly forced electronic oscillator

This paper examines an electronic oscillator forced by a pseudo-random noise signal. We give evidence of the existence of one or more random attractors for the system depending on noise amplitude and system parameters. These random attractors may appear to be random fixed points or random chaotic attractors. In the latter case, we observe a form of intermittent synchronization of the response of the system to the noise signal. We show how this can be understood as on–off intermittency in an extended system.

Measurements of normal incidence surface impedance using the single transfer function method with multitone periodic random noise signal

Commonly used signals for determining the transfer function of a linear filter are pure tone excitation, white noise, or a pseudorandom noise (MLS) signal. However, it is known that the accuracy of this measurement depends strongly on the kind of signal used. In order to try to improve the quality of the measurement, multitone periodic random noise signal properties are investigated in the case of the normal incidence surface impedance measurement. Kundt’s tubes and free-field impedance results using a single microphone transfer function method are given in a large frequency range (20–4000 Hz) for a multitone periodic random noise signal. These results are compared with those obtained with pure tone, white noise, and MLS signal excitation. Also, the influence of noise immunity is investigated for each type of signal.

Spatial coherence measurement of sound in the northwest Pacific Ocean

An experiment on the transverse horizontal spatial coherence of sound propagating in the ocean was performed jointly by Chinese and Russian acousticians in the northwest Pacific Ocean in June 1990. Three hydrophones with spacings of 270 and 130 m were put in the water at a 30‐m depth. The acoustic source with four cw (from 109 to 860 Hz) and a broadband pseudorandom noise signal was drifted at a depth of 100 m. Part of the measurement results of up to 140 km are presented in this paper. It seems that the spatial coherence was related to the amplitude of the received signals and rises considerably in convergence zones.

Delay detection method using cross-spectrum for multitransmitter simulcasting

The authors propose a precise delay detection method using cross-spectrum which can be adopted for phase synchronisation of high speed multitransmitter simulcasting mobile radio communication systems. It is also shown that the detection error of this method is improved by pseudorandom noise (PN) signals and the minimum square error estimation.

Effects of interaural time delays of noise stimuli on low-frequency cells in the cat's inferior colliculus. I. Responses to wideband noise

We examined the responses of low-frequency neurons in the central nucleus of the inferior colliculus (ICC) of the cat to interaurally delayed, wideband noise stimuli. The stimuli were pseudorandom noise signals that were generated digitally with a nominal bandwidth of 60-4,000 Hz. We also compared the responses to noise with those obtained from interaural phase differences of pure tones. We studied 144 neurons with characteristic frequencies below 2.5 kHz. Eighty-five percent (85%) of these were sensitive to changes in both interaural time differences (ITDs) of noise and interaural phase differences of pure tones, only 2% were sensitive to one stimulus but not the other, and the remainder were insensitive to both stimuli. For most cells the discharge rate was modulated in an approximately cyclic fashion by changes in ITDs of the wideband noise stimuli. The maximal spike counts often occurred near zero ITD, and there was considerable variability in the nature of the cycling, though it usually disappeared for ITDs greater than +/- 4,000 microseconds. The position of the central peak was usually (65%) within the physiologically relevant range of +/- 400 microseconds, and most (80%) occurred at positive ITDs, which corresponded to delays to the ipsilateral stimulus. In general, the shapes of the responses were not affected by changes in stimulus level above threshold. As long as identical noises were delivered to both ears, the responses were not sensitive to the particular noise stimulus used. When uncorrelated noises were delivered to the two ears, there was no sensitivity to ITDs. Composite curves were computed by linear summation of the responses to ITDs of pure tones at frequencies spaced at equal intervals throughout each cell's response area. The shapes of composite curves were similar to the responses of the same cell to ITDs of wideband noise stimuli. The positions of the central peaks of these two functions were highly correlated (r = 0.91, slope = 0.97). The values of characteristic delay and characteristic phase computed from the tonal responses were found to be good indicators of the shapes of the noise delay curves. Characteristic phases (CPs) near zero were associated with noise delay curves symmetric about the central peak, CPs near 0.5 cycles with those symmetric about the trough, while CPs between 0 and 0.5 or between 0.5 and 1.0 had noise delay curves that were asymmetric with a prominent trough to the left or right, respectively, of the central peak.(ABSTRACT TRUNCATED AT 400 WORDS)

Correlation method for determination of the time constants of impedances applied to electrical model networks and to a liquid capacitor

A correlation method is described for analysis of electrical impedances. The impedance is investigated as part of a four-terminal network, allowing general system analysis techniques to be applied. With a pseudorandom noise signal as input the measured cross-correlation function corresponds, under certain conditions, to the impulse response of the four-terminal network and contains the information about the network components via the time constants of the four-terminal network. The method has been applied to electrical two-terminal networks and to a liquid capacitor filled with a solution of poly- gamma -benzyl-L-glutamate in 1,2-dichloroethane. The latter application demonstrates that information on the dynamic behaviour of a chemical system and its changes with time can be obtained directly.

A review of distortion and its measurement in p.c.m. telephony systems

Pulse code modulation systems as used in telephony networks are briefly described with particular regard to the inherent quantizing distortion (q.d.). Test methods for the evaluation of signal to q.d. ratio, from analogue input to analogue output, are reviewed. Three test stimuli are considered and their advantages and disadvantages discussed. The three stimuli are a sinusoid, a band-limited noise signal and a band-limited pseudo-random noise signal.

Decomposition technique for acquiring combined pseudorandom-noise signals

A new technique for fast acquisition of pseudorandom-noise (p.r.n.) signals is derived. By considering that the period of a long combined p.r.n. sequence is equal to the product of the periods of its component sequences, we found that phase synchronisation can be achieved much easier after directly decomposing the received p.r.n. sequence into its component sequences, thus eliminating the sequential search required by the existing methods. Advantages of the proposed technique are: (a) it is easy to implement, (b) there are low probabilities of false alarm and false dismissal, and (c) in the minimising of the correlation time. It could not only significantly improve the existing p.r.n. ranging and tracking systems, but also could strengthen and simplify spread-spectrum communication systems, especially in the secure-code generators and logical-minimisation areas. Examples are presented and discussed.

Use of high-resolution pseudorandom noise signals to isolate individual underwater sound paths

In the course of the study of the transmission properties of broad-band pseudorandom noise signals as a function of range, water depth, and other environmental parameters, relationship between correlation peak time differences and multipath time differences was determined. Illustrations of the measured cross correlation between a reference and high-resolution pseudorandom noise signal versus time and calculated ray paths are presented. Peak correlation values range from 0.31 to 0.63 for the demonstration data. Only minor discrepancies were observed in the measured time differences between the correlation peaks and those calculated from XBT data.