Apparatus and method for baseband detection and equalization of information signals

Claim 3

The method of claim 1 including the additional step of combining said equalized in-phase and out-of-phase components to reproduce at baseband said information signal.

Claim 4

The method of claim 2 for use in a binary differentially coherent phase shift-keyed system wherein said information signal is characterized by a plurality of time slots and said combining step comprises first comparing the sign of the differential phase shift in one time slot of one of said components with the sign of the differential phase shift in the previous time slot of the other of said components and generating a positive output when both of the compared signs are alike and a negative output when different, and secondly, comparing the sign of the differential phase shift in one time slot of the other of said components with the sign in the previous time slot of said one component and generating a positive output when said compared signs are equal and a negative output when different, the output of said second comparison following in time the output of said first comparison, said comparisons being repeated until all of the differential phase information is recovered.

Claim 5

The method of claim 1 wherein said decomposing and carrier removing steps comprise the steps of: dividiNg said information signal into two separate signals in phase quadrature with each other, generating a local oscillator signal phase locked to the carrier of said information signal, dividing said local oscillator signal into two separate signals in phase quadrature with each other, phase shifting by 90* one of said separate local oscillator signals, simultaneously applying one of said separate information signals and said phase shifted local oscillator signal to a first homodyne to generate the in-phase component of said information signal at baseband, and simultaneously applying the other of said separate information signals and said other separate local oscillator signal to a second homodyne to generate the out-of-phase component of said information signal at baseband.

Claim 6

The method of claim 1 including the step of setting Alpha n and Beta n to levels equal to the coefficients of the Fourier series of the Fourier transform of the system component producing said distortion.

Claim 7

The method of claim 1 wherein each of said first and second pluralities of separate transmission paths comprises a transversal equalizer including time delay, attenuating and summing means, and including the steps of sampling said equalized in-phase and out-of-phase components and setting Alpha n and Beta n to values such that the difference between the inverse Fourier transform of said equalizer and said undistorted signal is equal to zero at a sufficient number of sampling instants to allow satisfactory transmission.

Claim 8

Apparatus for the detection and equalization of carrier information signals having arbitrary distortion and modulation comprising, means for removing the carrier from the distorted information signal by a linear mixing process, means for decomposing said distorted signal into distorted conjugate in-phase and out-of-phase components, means for directing each of said distorted conjugate components into a first and second plurality of separate transmission paths, means for adjusting the difference in time delay between adjacent ones of said paths within each of said pluralities to be not greater than the reciprocal of the bandwidth over which equalization is desired, means for attenuating the portion of said in-phase distorted component in the nth of its first plurality of paths by an amount + Alpha n and in the nth of its second plurality of paths by an amount + Beta n, means for attenuating the portion of said out-of-phase distorted component in the nth of its first plurality of paths by an amount - Beta n and in the nth of its second plurality of paths by an amount + Alpha n, means for summing said attenuated in-phase components of its first plurality of paths with said attenuated out-of-phase components of its first plurality of paths to produce an equalized baseband in-phase component of said information signal, and means for summing said attenuated in-phase components of its second plurality of paths with said attenuated out-of-phase components of its second plurality of paths to produce an equalized baseband out-of-phase component of said information signal.

Claim 9

Apparatus for the detection and equalization of carrier information signals having arbitrary distortion and modulation comprising, means for removing the carrier from the distorted information signal by a linear mixing process, means for decomposing said distorted signal into distorted conjugate in-phase and out-of-phase components, means for directing each of said distorted conjugate components into a first and second plurality of separate transmission paths, means for adjusting the difference in time delay between adjacent ones of said paths within each of said pluralities to be not greater than the reciprocal of the bandwidth over which equalization is desired, means for attenuating the portion of said in-phase distorted component in the nth of its first plurality of paths by an amount + Alpha n and in the nth of its second plurality of paths by an amount + Beta n, means for attenuating the portion of said out-of-phase distorted component in the nth of its first plurality of paths by an amount - Beta n and in the nth of its second plurality of paths by an amount + Alpha n, means for summing said attenuated in-phase components of its first plurality of paths with said attenuated out-of-phase components of its first plurality of paths to produce an equalized baseband in-phase component of said information signal, and means for summing said attenuated in-phase components of its second plurality of paths with said attenuated out-of-phase components of its second plurality of paths to produce an equalized baseband out-of-phase component of said information signal.

Claim 10

The apparatus of claim 7 in combination with means for combining said equalized in-phase and out-of-phase components to reproduce at baseband said information signal.

Claim 11

The apparatus of claim 8 for use in a binary differentially coherent phase shift-keyed system wherein said information signal is characterized by a plurality of time slots and said combining means comprises a comparator which first compares the sign of the differential phase shift in one time slot of one of said components with the sign of the differential phase shift in the previous time slot of the other of said components and generates a positive output when said compared signs are alike and a negative output when said signs are different, and secondly, compares the sign of the differential phase shift in one time slot in said other component with the sign in the previous time slot in said one component and generates a positive output when said compared signs are the same and a negative output when different, the output of said second comparison following in time the output of said first comparison, said comparisons being repeated until all of the differential phase information is recovered.

Claim 12

The apparatus of claim 7 wherein said means for decomposing said signal and removing said carrier comprises, hybrid coupler means for dividing said information signal into two separate signals in phase quadrature with each other, means for generating a local oscillator signal, means for phase-locking said local oscillator signal to the carrier of said information signal, hybrid coupler means for dividing said phase-locked local oscillator signal into two separate signals in phase quadrature with each other, means for phase shifting by 90* one of said separate local oscillator signals, a first and a second homodyne, means for simultaneously applying one of said separate information signals and said phase shifted local oscillator signal to said first homodyne to generate the in-phase component of said information signal at baseband, and means for simultaneously applying the other of said separate information signals and said other separate local oscillator signal to said second homodyne to generate the out-of-phase component of said information signal at baseband.

Claim 13

The apparatus of claim 7 wherein said means for directing each of said distorted conjugate signal components into a first and second plurality of separate transmission paths comprises first and second transversal equalizers.

Claim 14

The apparatus of claim 11 wherein each of said transversal equalizers comprise: a plurally tapped delay line, a separate transmission path connected to each of the taps of each of said delay lines, each of said attenuating means being a part of a separate one of said transmission paths, the location of said taps being chosen such that the difference in time delay between adjacent paths is not greater than the reciprocal of the bandwidth over which equalization is desired.

Claim 15

The apparatus of claim 11 in combination with means for sampling said equalized baseband in-phase and out-of-phase components and wherein Alpha n and Beta n are set to levels such that the difference between the inverse Fourier transform of each of said equalizers and said undistorted information signal is equal to zero at a sufficient number of sampling instants.

Claim 16

The apparatus of claim 7 wherein Alpha n and Beta n are set to levels equal to the coefficients of the Fourier series of the Fourier transform of the system component producing said distortion.