scispace - formally typeset
Search or ask a question

Showing papers on "Noise reduction published in 1969"


Journal ArticleDOI
TL;DR: The feedback coding problem for additive noise systems, in which the noise may be colored, nonstationary, and correlated between channels, is formulated in terms of arbitrary linear operations at the transmitting and receiving points, providing a unified approach for deriving new results.
Abstract: The feedback coding problem for additive noise systems, in which the noise may be colored, nonstationary, and correlated between channels, is formulated in terms of arbitrary linear operations at the transmitting and receiving points. This rather general linear formulation provides a unified approach for deriving new results, as well as previous results obtained under more restrictive assumptions, in a straightforward manner. Thus the sequential form of the optimum linear feedback code with an average power constraint on the transmitter is derived for noiseless feedback but forward noise of arbitrary covariance. It is shown explicitly that noiseless feedback increases the capacity of a channel with colored noise. The noisy feedback problem is considered and upper and lower bounds on the performance presented.

117 citations


Journal ArticleDOI
TL;DR: In this paper, the authors derived the wide-band signal-to-noise ratio of a tape recorder equalized flat, which is inversely dependent upon the square of a bandwidth.
Abstract: Using the Wiener autocorrelation theorem, the noise power spectrum of the pole strength in a thin lamina of an erased tape is shown to be approximately white. The noise power spectrum of the reproduce head voltage is calculated for a thick tape and compared with the signal power. The wide-band signal-to-noise ratio of a tape recorder equalized flat is deduced and expressed in very simple forms, which are inversely dependent upon the square of a bandwidth. Notably, in this special case the wide-band result is independent of reproduce head-to-tape spacing. Numerical examples demonstrate that this simple theory yields results in excellent agreement with practice.

82 citations


Patent
Allan Carlson1
02 Jul 1969
TL;DR: In this paper, an apparatus and methods for reducing pattern noise in a vidicon type camera tube and particularly a camera tube system embodying a thermal detector array for viewing infrared radiation is described.
Abstract: This invention relates to an apparatus and methods for reducing pattern noise in a vidicon type camera tube and particularly a vidicon camera tube system embodying a thermal detector array for viewing infrared radiation. A chopper is placed in front of the detector and switched open and shut. Thus, the vidicon target receives alternatively signal plus noise and noise alone. When receiving the noise alone, the target is overcharged above a bias level by an external source to an amount equal to the discharge due to the noise. Therefore, when the target receives signal plus noise, the noise components will subtract out.

9 citations



Patent
14 Nov 1969
TL;DR: In this article, a system for reducing noise generated in an electrical transformer due to changing of size and shape of the ferromagnetic core when excited with alternating electric current was proposed.
Abstract: A system for reducing noise generated in an electrical transformer due to changing of size and shape of the ferromagnetic core when excited with alternating electric current. The noise reduction system comprises attaching flexible fibers to parts of the ferromagnetic core and parts of the housing or casing of the transformer. The flexible fibers absorb energy from the air column set up by the core when it changes size and shape and reduces the effectiveness of the air column in setting up objectional audible noise.

5 citations


Patent
28 Jul 1969

4 citations


Proceedings Article
01 Jan 1969
TL;DR: Fourier and Hadamard transformation codings for multidimensional data channel noise immunity and bandwidth reduction are presented.
Abstract: Fourier and Hadamard transformation codings for multidimensional data channel noise immunity and bandwidth reduction

3 citations


Journal ArticleDOI
01 Mar 1969
TL;DR: This article describes a digital method of generating white Gaussian noise with the spectral density A 2 uniformly distributed over all frequencies, and sets it up in practical non-real-time as well as in realtime simulations.
Abstract: The acquisition and processing of data is often affected by randomly fluctuating variables with the result that the data values are a blend of signal and noise. Thus a realistic simulation of the physical system must also purposely add to the deterministic values of the signal an analogous amount and type of noise. Since the physical system which is being simulated passes only finite-frequency signals, the noise can be simulated as a low-pass pseudo-white Gaussian noise with a certain RMS value, sampled at certain (equidistant) intervals of time. This article describes a digital method of generating such a noise. The mathematical derivation of this algorithm is rather lengthy and can be found in references (1) and (2), which should be credited with its original derivation. All the author did was to realize the usefulness and the flexibility of this tool, check it out for validity by means of autocorrelation and power-spectrum-density analysis, and set it up in practical non-real-time as well as in realtime simulations. The source of the noise is assumed to be white Gaussian noise with the spectral density A 2 uniformly distributed over all frequencies, as in figure 1.

3 citations


Journal ArticleDOI
TL;DR: In this article, the use of transmission line transformers for the suppression of ground loop induced noise is investigated, and a noise reduction of 100 was achieved in the experiment described, achieving a power loss of only 5 dB.

Patent
05 Feb 1969
TL;DR: In this paper, a method and system for producing a multidimensional recording of a multivariable data signal with a minimum amount of lowfrequency noise and interference in the signal is presented.
Abstract: A recording method and system is disclosed which provides for selective reprocessing and filtering of the data to obtain the optimum signal-to-noise ratio without a corresponding loss of the data range or fidelity. More particularly, an improved method and system is disclosed for producing a multidimensional recording of a multivariable data signal with a minimum amount of low-frequency noise and interference in the signal.