Apparatus for improving the signal to noise ratio of signals received at two antennas

Claim 1

Device for improving the signal-to-noise ratio of electrical signals received on two aerials, applicable in the case when the useFul signals occupy a narrow band of frequencies around a mean value fo, and when the noise signals B1 and B2 received on the two aerials are at least partially correlated, comprising first means responsive to the signals received at said aerials for providing a pair of useful signals from each aerial identical to a common value S, so as to obtain at the output of the said means signals 1 S + B1 and Sigma 2 S + B2 a first circuit connected to said first means for generating a voltage u as a linear function of the correlation coefficient of the noise signals B1 and B2 and a voltage v proportional to the correlation coefficient of the noise signals B1 and B2 arranged in phase quadrature with respect to one another, a second circuit connected to said first circuit comprising an auxiliary generator of a given frequency F, means for obtaining from this generator and said first circuit sinusoidal voltages x and y of frequency F NOT = fo and of amplitudes respectively proportional to u and v, and means for forming voltages pi 1 x + y and pi 2 x y, and means responsive to said second circuit for chopping the voltages 1 and pi 2 and for applying them to respective first inputs of two polarity-coincidence correlators whose second inputs receive respectively voltages Sigma 1 and Sigma 2 resulting from chopping Sigma 1 and Sigma 2, the outputs of these two correlators being respectively connected to two inputs of a summation element, followed by a band-pass filter at whose output is obtained the required useful signal.

Claim 3

An apparatus for improving the signal to noise ratio of an information signal which contains a useful component and a noise component, said signal being received at a plurality of pick-up elements, comprising: first means for producing original electrical signals in response to said information signal received on said plurality of pick-up elements; second means responsive to said electrical signals for generating therefrom a first electrical signal representative of the linear correlation coefficient of the noise components in said original electrical signals, and a second electrical signal representative of the correclation coefficient of said noise components separated in phase-quadrature; third means responsive to said first and second electrical signals for modifying said first and second electrical signals and for generating sum and difference signals representative of the sum and difference respectively of the modified forms of said first and second electrical signals; and fourth means responsive to said first and second electrical signals and responsive to said sum and difference signals for generating an output signal representative of said information signal containing substantially the same useful component but having a noise component substantially attenuated, whereby the signal to noise ratio of said information signal is increased.

Claim 4

An apparatus for improving the signal to noise ratio of an information signal which contains a useful component and a noise component, said signal being received at a plurality of pick-up elements, comprising: first means for producing original electrical signals in response to said information signal received on said plurality of pick-up elements; second means responsive to said electrical signals for generating therefrom a first electrical signal representative of the linear correlation coefficient of the noise components in said original electrical signals, and a second electrical signal representative of the correclation coefficient of said noise components separated in phase-quadrature; third means responsive to said first and second electrical signals for modifying said first and second electrical signals and for generating sum and difference signals representative of the sum and difference respectively of the modified forms of said first and second electrical signals; and fourth means responsive to said first and second electrical signals and responsive to said sum and difference signals for generating an output signal representative of said information signal containing substantially the same useful component but having a noise component substantially attenuated, whereby the signal to noise ratio of said information signal is increased.