Passband equalizer for phase-modulated data signals

Claim 2

A transversal equalizer for a phase-modulated data transmission channel causing distorted signals comprising a synchronously tapped delay line accepting distorted signals from said channel; a pair of adjustable attenuators connected to each tap on said delay line; a summation circuit for forming an equalized output signal; means for connecting one of each pair of attenuators directly and the other of each pair through a 90* phase shifter to said summation circuit; means for developing an error signal from the difference in magnitude between a 90-degree vector component of an actual output signal from said summation circuit and the corresponding vector component of an idealized output signal; and means for correlating said error signal with distorted signals from said channel directly, and with distorted signals phaseshifted by 90 degrees, at each tap on said delay line to generate control signals for the respective ones and others of each pair of said attenuators.

Claim 3

The transversal equalizer defined in claim 1 in which a second synchronously tapped delay line in series with a 90* phase shifter provides quadrature-related tap signals for correlation with said error signal to generate control signals for said attenuators connected to said summation circuit through said first-mentioned 90* phase shifter.

Claim 4

The transversal equalizer defined in claim 1 in which said means for developing an error signal comprises a comparator with a predetermined threshold level set at the magnitude of the equal quadrature-related components of an ideal phase-modulated reference signal.

Claim 5

The transversal equalizer defined in claim 1 in which said means for correlating said error signal with the several distorted signals appearing at taps on said delay line comprises Exclusive-OR gates.

Claim 6

An adaptive transversal equalizer for a phase-modulated data transmission channel comprising a first delay line with synchronously spaced taps thereon and having a direct connection to said channel; a first 90-degree phase-shift circuit accepting signals from said channel; a second delay line with synchronously spaced taps thereon for receiving phase-shifted channel signals from said first phase-shift circuit; a first plurality of adjustable attenuators connected to the taps on said first delay line; first combining means for signals traversing said first plurality of attenuators; a second plurality of adjustable attenuators connected to taps on said first delay line; second combining means for signals traversing said second plurality of attenuators; third combining means for signals traversing said first and second combining means for producing an equalized output signal; a second 90* phase-shift circuit in tandem between said second and third combining means; threshold slicing means responsive to signals traversing said second phase-shift circuit for deriving an error signal as the difference between the predetermined threshold level related to the magnitude of equal-length quadrature components of an ideal received signal and signals traversing said second phase-shift circuit; a first plurality of correlating means having first and second inputs, said first inputs being connected to individual taps on said first delay line for providing control signals to said first plurality of adjustable attenuators; a second plurality of correlating means having first and second inputs, said first input being connected to individual taps on said second delay line for providing control signals to said second plurality of adjustable attenuators; and means for applying said error signal to the second inputs of said first and second pluralities of correlating means in common.

Claim 7

An adaptive transversal equalizer for a phase-modulated data transmission channel comprising a first delay line with synchronously spaced taps thereon and having a direct connection to said channel; a first 90-degree phase-shift circuit accepting signals from said channel; a second delay line with synchronously spaced taps thereon for receiving phase-shifted channel signals from said first phase-shift circuit; a first plurality of adjustable attenuators connected to the taps on said first delay line; first combining means for signals traversing said first plurality of attenuators; a second plurality of adjustable attenuators connected to taps on said first delay line; second combining means for signals traversing said second plurality of attenuators; third combining means for signals traversing said first and second combining means for producing an equalized output signal; a second 90* phase-shift circuit in tandem between said second and third combining means; threshold slicing means responsive to signals traversing said second phase-shift circuit for deriving an error signal as the difference between the predetermined threshold level related to the magnitude of equal-length quadrature components of an ideal received signal and signals traversing said second phase-shift circuit; a first plurality of correlating means having first and second inputs, said first inputs being connected to individual taps on said first delay line for providing control signals to said first plurality of adjustable attenuators; a second plurality of correlating means having first and second inputs, said first input being connected to individual taps on said second delay line for providing control signals to said second plurality of adjustable attenuators; and means for applying said error signal to the second inputs of said first and second pluralities of correlating means in common.