Feedforward nonlinear equalization of modulated data signals

Claim 2

In an arrangement responsive to samples of a received modulated data signal for forming decisions as to the values of data symbols contained in said signal, each of said samples being represented by a complex number, that improvement which comprises means (51-55, 61-65) for forming a plurality of signal products associated with an individual one of said samples, each multiplicand of each product being derived from a respective one of said samples, each said respective one of said samples bearing a predetermined temporal relationship to said individual one of said samples, and at least one multiplicand of individual ones of said signal products being the complex conjugate of the sample from which said one multiplicand is derived, means (71-75) for multiplying each of said products by an associated coefficient to form a plurality of weighted products, means (81-86) for combining said weighted products with each other to generate a feedforward nonlinear signal, and means (12, 14, 17, 43) for forming an individual one of said decisions in response to said feedforward nonlinear signal.

Claim 3

The invention of claim 1 wherein said modulated data signal is of the type in which both the carrier phase and amplitude are information-bearing.

Claim 4

The invention of claim 1 wherein said modulated data signal is a quadrature amplitude modulated signal.

Claim 5

In an arrangement responsive to samples of a received modulated data signal for forming decisions as to thee values of data symbols contained in said signal, said signal being of the type in which both the carrier phase and amplitude are information bearing and each of said samples being represented by a complex number, that improvement which comprises means (51-55, 61-65) for forming a plurality of signal products associated with an individual one of said samples, each multiplicand of each product being derived from a respective one of said samples, each said respective one of said samples bearing a predetermined temporal relationship to said individual one of said samples, and at least one multiplicand of individual ones of said signal products being the complex conjugate of the sample from which said one multiplicand is derived, means (71-75 for multiplying each of said products by an associated coefficient to form a plurality of weighted products, means (11, 43) for multiplying predetermined ones of said samples by respective associateed coefficients and for summing the resulting products with said weighted products to form a composite feedforward signal and means (12, 14, 17) responsive to said composite feedforward signal for forming an individual one of said decisions.

Claim 6

In an arrangement responsive to samples of a received modulated data signal for forming decisions as to thee values of data symbols contained in said signal, said signal being of the type in which both the carrier phase and amplitude are information bearing and each of said samples being represented by a complex number, that improvement which comprises means (51-55, 61-65) for forming a plurality of signal products associated with an individual one of said samples, each multiplicand of each product being derived from a respective one of said samples, each said respective one of said samples bearing a predetermined temporal relationship to said individual one of said samples, and at least one multiplicand of individual ones of said signal products being the complex conjugate of the sample from which said one multiplicand is derived, means (71-75 for multiplying each of said products by an associated coefficient to form a plurality of weighted products, means (11, 43) for multiplying predetermined ones of said samples by respective associateed coefficients and for summing the resulting products with said weighted products to form a composite feedforward signal and means (12, 14, 17) responsive to said composite feedforward signal for forming an individual one of said decisions.

Claim 7

In an arrangement responsive to complex samples of a received modulated data signal for forming decisions as to the values of data symbols represented by said signal, both the carrier phase and amplitude of said signal being information-bearing, that improvement which comprises means (51-55, 61-65) operative during each of a plurality of successive sampling periods for forming a plurality of signal products associated with an individual one of said samples, each multiplicand of each product being derived from a respective one of said samples, each said respective one of said samples bearing a predetermined temporal relationship to said individual one of said samples, and at least one multiplicand of individual ones of said signal products being the complex conjugate of the sample from which said one multiplicand is derived, means (71--75) operative during each of said sampling periods for multiplying said products by respective associated coefficients to form a plurality of weighted products, the value of each of said coefficients during an individual one of said sampling periods being its value during a preceding sampling period modified by a correction factor, means (81-86) for combining said weighted products with each other to generate a feedforward nonlinear signal, means (11, 43) responsive to predetermined ones of said samples for generating a feedforward linear signal and for combining it with said feedforward nonlinear signal to form a composite feedforward signal, and means (12, 14, 17) for forming an individual one of said decisions in response to said composite feedforward signal.

Claim 8

In an arrangement responsive to complex samples of a received modulated data signal for forming decisions as to the values of data symbols represented by said signal, both the carrier phase and amplitude of said signal being information-bearing, that improvement which comprises means (51-55, 61-65) operative during each of a plurality of successive sampling periods for forming a plurality of signal products associated with an individual one of said samples, each multiplicand of each product being derived from a respective one of said samples, each said respective one of said samples bearing a predetermined temporal relationship to said individual one of said samples, and at least one multiplicand of individual ones of said signal products being the complex conjugate of the sample from which said one multiplicand is derived, means (71--75) operative during each of said sampling periods for multiplying said products by respective associated coefficients to form a plurality of weighted products, the value of each of said coefficients during an individual one of said sampling periods being its value during a preceding sampling period modified by a correction factor, means (81-86) for combining said weighted products with each other to generate a feedforward nonlinear signal, means (11, 43) responsive to predetermined ones of said samples for generating a feedforward linear signal and for combining it with said feedforward nonlinear signal to form a composite feedforward signal, and means (12, 14, 17) for forming an individual one of said decisions in response to said composite feedforward signal.

Claim 9

The invention of claim 5 further comprising means means (12) for demodulating said composite feedforward signal, means (17) for generating a quantized data signal in response to the demodulated composite feedforward signal, means for forming an error signal (20) in response to said demodulated signal and said quantized data signal, and means (28) for modulating said error signal at the carrier frequency of said modulated data signal to form a modulated error signal, said correction factor for an individual one of said coefficients being a function of the product associated with said individual one of said coefficients during said preceding sampling period and of the modulated error signal for said preceding sampling period.

Claim 10

In a method for forming decisions as to the values of data symbols contained in a received modulated data signal, said decisions being formed in response to complex samples of said received signal, that improvement which comprises the steps of forming a plurality of signal products associated with an individual one of said samples, each multiplicand of each product being derived from a respective one of said samples, each said respective one of said samples bearing a predetermined temporal relationship to said individual one of said samples, and at least one multiplicand of individual ones of said signal products being the complex conjugate of the sample from which said one multiplicand is derived, multiplying each of said products by an associated coefficient to form a plurality of weighted products, combining said weighted products with each other to generate a feedforward nonlinear signal, and forming an individual one of said decisions in response to said feedforward nonlinear signal.

Claim 11

In a method for forming decisions as to the values of data symbols contained in a received modulated data signal, said decisions being formed in response to complex samples of said received signal, that improvement which comprises the steps of forming a plurality of signal products associated with an individual one of said samples, each multiplicand of each product being derived from a respective one of said samples, each said respective one of said samples bearing a predetermined temporal relationship to said individual one of said samples, and at least one multiplicand of individual ones of said signal products being the complex conjugate of the sample from which said one multiplicand is derived, multiplying each of said products by an associated coefficient to form a plurality of weighted products, combining said weighted products with each other to generate a feedforward nonlinear signal, and forming an individual one of said decisions in response to said feedforward nonlinear signal.

Claim 12

The invention of claim 7 wherein said modulated data signal is of the type in which both the carrier phase and amplitude are modulated.

Claim 13

The invention of claim 7 wherein said modulated data signal is a quadrature amplitude modulated signal.

Claim 14

In a method for forming decisions as to the values of data symbols contained in a received quadrature amplitude modulated data signal, said decisions being formed in response to complex samples of said received signal, that improvement which comprises the steps of forming a plurality of signal products associated with an individual one of said samples, each multiplicand of each product being derived from a respective one of said samples, each said respective one of said samples bearing a predetermined temporal relationship to said individual one of said samples, and at least one multiplicand of individual ones of said signal products being the complex conjugate of the sample from which said one multiplicand is derived, multiplying each of said products by an associated coefficient to form a plurality of weighted products, combining said weighted products with each other to generate a feedforward nonlinear signal, generating a feedforward linear signal in response to predetermined ones of said samples combining said feedforward linear signal with said feedforward nonlinear signal to form a composite feedforward signal, and forming an individual one of said decisions in response to said composite feedforward signal.

Claim 15

In a method for forming decisions as to the values of data symbols contained in a received quadrature amplitude modulated data signal, said decisions being formed in response to complex samples of said received signal, that improvement which comprises the steps of forming a plurality of signal products associated with an individual one of said samples, each multiplicand of each product being derived from a respective one of said samples, each said respective one of said samples bearing a predetermined temporal relationship to said individual one of said samples, and at least one multiplicand of individual ones of said signal products being the complex conjugate of the sample from which said one multiplicand is derived, multiplying each of said products by an associated coefficient to form a plurality of weighted products, combining said weighted products with each other to generate a feedforward nonlinear signal, generating a feedforward linear signal in response to predetermined ones of said samples combining said feedforward linear signal with said feedforward nonlinear signal to form a composite feedforward signal, and forming an individual one of said decisions in response to said composite feedforward signal.

Claim 16

In a method for forming decisions as to the values of data symbols represented by a received modulated data signal in which both the carrier phase and amplitude are information-bearing, said decisions being formed in response to samples of said received signal each of which is represented by a complex number, that improvement which comprises the steps of forming during each of a plurality of successive sampling periods a plurality of signal products associated with an individual one of said samples, each multiplicand of each product being derived from a respective one of said samples, each said respective one of said samples bearing a predetermined temporal relationship to said individual one of said samples, and at least one multiplicand of individual ones of said signal products being the complex conjugate of the sample from which said one multiplicand is derived, multiplying said products by respective associated coefficients during each of said sampling periods to form a plurality of weighted products, the value of each of said coefficients during an individual one of said sampling periods being its value during the preceding sampling period modified by a correction factor, combining said weighted products with each other to generate a feedforward nonlinear signal, and forming an individual one of said decisions in response to a composite signal which includes said feedforward nonlinear signal.

Claim 17

In a method for forming decisions as to the values of data symbols represented by a received modulated data signal in which both the carrier phase and amplitude are information-bearing, said decisions being formed in response to samples of said received signal each of which is represented by a complex number, that improvement which comprises the steps of forming during each of a plurality of successive sampling periods a plurality of signal products associated with an individual one of said samples, each multiplicand of each product being derived from a respective one of said samples, each said respective one of said samples bearing a predetermined temporal relationship to said individual one of said samples, and at least one multiplicand of individual ones of said signal products being the complex conjugate of the sample from which said one multiplicand is derived, multiplying said products by respective associated coefficients during each of said sampling periods to form a plurality of weighted products, the value of each of said coefficients during an individual one of said sampling periods being its value during the preceding sampling period modified by a correction factor, combining said weighted products with each other to generate a feedforward nonlinear signal, and forming an individual one of said decisions in response to a composite signal which includes said feedforward nonlinear signal.

Claim 18

The invention of claim 11 comprising the further steps of multiplying predetermined ones of said samples by respective associated coefficients and combining the resulting products with said feedforward nonlinear signal to form a composite feedforward signal, demodulating said composite feedforward signal, generating a quantized data signal in response to the demodulated composite feedforward signal, forming an error signal in response to said demodulated signal and said quantized data signal, and modulating said error signal at the carrier frequency of said modulated data signal to form a modulated error signal, said correction factor for an individual one of said coefficients being a function of the product associated with said individual one of said coefficients during said preceding sampling period and of the modulated error signal for said preceding sampling period.

Claim 19

In an arrangement for receiving a succession of complex samples of a modulated data signal of the type in which both the carrier amplitude and phase are information-bearing, the n th of said samples being R(n), said signal representing a plurality of data symbols, the method which comprises the steps of generating an equalized feedforward nonlinear signal P(n) corresponding to said sample R(n), said signal P(n) including the terms ##EQU7## * indicating complex conjugate, the coefficients W j .sbsb.1.sub.,j.sbsb.2.sup.(1)* (n) and W j .sbsb.3.sub.,j.sbsb.4.sup.(2)* (n) having respective values associated with said sample R(n), and the index pairs (j 1 ,j 2 ) and (j 3 ,j 4 ) having respective sets of predetermined values, and forming a decision A(n) as to the value of an individual one of said data symbols in response to said signal P(n).

Claim 20

In an arrangement for receiving a succession of complex samples of a modulated data signal of the type in which both the carrier amplitude and phase are information-bearing, the n th of said samples being R(n), said signal representing a plurality of data symbols, the method which comprises the steps of generating an equalized feedforward nonlinear signal P(n) corresponding to said sample R(n), said signal P(n) including the terms ##EQU7## * indicating complex conjugate, the coefficients W j .sbsb.1.sub.,j.sbsb.2.sup.(1)* (n) and W j .sbsb.3.sub.,j.sbsb.4.sup.(2)* (n) having respective values associated with said sample R(n), and the index pairs (j 1 ,j 2 ) and (j 3 ,j 4 ) having respective sets of predetermined values, and forming a decision A(n) as to the value of an individual one of said data symbols in response to said signal P(n).

Claim 21

The invention of claim 13 wherein said decision-generating step is comprised of the steps of forming a demodulated signal Y(n) in response to at least said signal P(n) and quantizing said signal Y(n) to generate said decision A(n), and wherein said method is comprised of the further steps of forming a modulated error signal J * (n) in response to said signal Y(n) and said decision A(n), and updating the coefficients W j .sbsb.1.sub.,j.sbsb.2.sup.(1)* (n) and W j .sbsb.3.sub.,j.sbsb.4.sup.(2)* (n) in accordance with ##EQU8## β.sub. (n) and β 2 (n) being selected scaling factors.

Claim 22

The invention of claim 14 comprising the further steps of generating an equalized feedforward linear signal Q(n), ##EQU9## the coefficients W i .sup.(0)* (n) having respective values associated with said sample R(n) and the index i having a set of predetermined values, said signal Y(n) being formed also in response to said signal Q(n), and updating the coefficients W i .sup.(0)* (n) in accordance with W.sub.i.sup.(0) (n+1)=W.sub.i.sup.(0) (n)-β.sub.0 (n)R(n-i)J.sup.* (n), β.sub. (n) being a selected scaling factor.

Claim 23

The invention of claim 13 wherein said signal P(n) further includes at least a selected one of the terms ##EQU10## the coefficients W k .sbsb.1.sub.,k.sbsb.2.sub.,k.sbsb.3.sup.(3)* (n), W k .sbsb.4.sub.,k.sbsb.5.sub.,k.sbsb.6.sup.(4)* (n) and W k .sbsb.7.sub.,k.sbsb.8.sub.,k.sbsb.9.sup.(5)* (n) having respective values associated with said sample R(n), and the index triples (k 1 ,k 2 ,k 3 ), (k 4 ,k 5 ,k 6 ) and (k 7 ,k 8 ,k 9 ) having respective sets of predetermined values.

Claim 24

The invention of claim 16 wherein said decision-generating step is comprised of the steps of forming a demodulated signal Y(n) in response to at least said signal P(n) and quantizing said signal Y(n) to generate said decision A(n), and wherein said method is comprised of the further steps of forming a modulated error signal J * (n) in response to said signal Y(n) and said decision A(n), and updating the coefficients W k .sbsb.1.sub.,k.sbsb.2.sub.,k.sbsb.3.sup.(3)* (n), W k .sbsb.4.sub.,k.sbsb.5.sub.,k.sbsb.6.sup.(4)* (n) and W k .sbsb.7.sub.,k.sbsb.8.sub.,k.sbsb.9.sup.(5)* (n) in accordance with ##EQU11## β.sub. (n), β 4 (n) and β 5 (n) being selected scaling factors.

Claim 25

In an arrangement for equalizing samples of a received modulated data signal, said modulated data signal being of the type in which both the carrier phase and amplitude are information-bearing, and each of said samples being represented by a complex number, that improvement which comprises means (51-55, 61-65) for forming a plurality of signal products associated with an individual one of said samples, each multiplicand of each product being derived from a respective one of said samples, each said respective one of said samples bearing a predetermined temporal relationship to said individual one of said samples, and at least one multiplicand of individual ones of said signal products being the complex conjugate of the sample from which said one multiplicand is derived, means (71-75) for multiplying each of said products by an associated coefficient to form a plurality of weighted products, and means (81-86) for combining said weighted products with each other to generate a feedforward nonlinear signal.

Claim 26

In an arrangement for equalizing samples of a received modulated data signal, said modulated data signal being of the type in which both the carrier phase and amplitude are information-bearing, and each of said samples being represented by a complex number, that improvement which comprises means (51-55, 61-65) for forming a plurality of signal products associated with an individual one of said samples, each multiplicand of each product being derived from a respective one of said samples, each said respective one of said samples bearing a predetermined temporal relationship to said individual one of said samples, and at least one multiplicand of individual ones of said signal products being the complex conjugate of the sample from which said one multiplicand is derived, means (71-75) for multiplying each of said products by an associated coefficient to form a plurality of weighted products, and means (81-86) for combining said weighted products with each other to generate a feedforward nonlinear signal.

Claim 27

In an arrangement for equalizing samples of a received quadrature amplitude modulated data signal, each of said samples being represented by a complex number, that improvement which comprises means (51-55, 61-65) for forming a plurality of signal products associated with an individual one of said samples, each multiplicand of each product being derived from a respective one of said samples, each said respective one of said samples bearing a predetermined temporal relationship to said individual one of said samples, and at least one multiplicand of individual ones of said signal products being the complex conjugate of the sample from which said one multiplicand is derived, means (71-75) for multiplying each of said products by an associated coefficient to form a plurality of weighted products, and means (81-86) for combining said weighted products with each other to generate a feedforward nonlinear signal.

Claim 28

In an arrangement for equalizing samples of a received quadrature amplitude modulated data signal, each of said samples being represented by a complex number, that improvement which comprises means (51-55, 61-65) for forming a plurality of signal products associated with an individual one of said samples, each multiplicand of each product being derived from a respective one of said samples, each said respective one of said samples bearing a predetermined temporal relationship to said individual one of said samples, and at least one multiplicand of individual ones of said signal products being the complex conjugate of the sample from which said one multiplicand is derived, means (71-75) for multiplying each of said products by an associated coefficient to form a plurality of weighted products, and means (81-86) for combining said weighted products with each other to generate a feedforward nonlinear signal.

Claim 29

The invention of claim 18 or claim 19 further comprising means (11, 43) responsive to predetermined ones of said samples for generating a feedforward linear signal and for combining it with said feedforward nonlinear signal to form a composite feedforward signal and means (12, 14, 17) responsive to said composite feedforward signal for recovering the modulated data from said samples.

Claim 30

In an arrangement for equalizing complex samples of a received modulated data signal in which both the carrier phase and amplitude are information-bearing, that improvement which comprises means (51-55, 61-65) operative during each of a plurality of successive sampling periods for forming a plurality of signal products associated with an individual one of said samples, each multiplicand of each product being derived from a respective one of said samples, each said respective one of said samples bearing a predetermined temporal relationship to said individual one of said samples, at at least one multiplicand of individual ones of said signal products being the complex conjugate of the sample from which said one multiplicand is derived, means (71-75) operative during each of said sampling periods for multiplying said products by respective associated coefficients to form a plurality of weighted products, the value of each of said coefficients during an individual one of said sampling being its value during a preceding sampling period modified by a correction factor, means (81-86) for combining said weighted products with each other to generate a feedforward nonlinear signal, means (11, 43) responsive to predetermined ones of said samples for generating a feedforward linear signal and for combining it with said feedforward nonlinear signal to form a composite feedforward signal, means (12) for demodulating said composite feedforward signal, means (17) for generating a quantized data signal in response to the demodulated composite feedforward signal, means for forming an error signal (20) in response to said demodulated signal and said quantized data signal, and means (28) for modulating said error signal at the carrier frequency of said modulated data signal to form a modulated error signal, said correction factor for an individual one of said coefficients being a function of the product associated with said individual one of said coefficients during said preceding sampling period and of the modulated error signal for said preceding sampling period.

Claim 31

In an arrangement for equalizing complex samples of a received modulated data signal in which both the carrier phase and amplitude are information-bearing, that improvement which comprises means (51-55, 61-65) operative during each of a plurality of successive sampling periods for forming a plurality of signal products associated with an individual one of said samples, each multiplicand of each product being derived from a respective one of said samples, each said respective one of said samples bearing a predetermined temporal relationship to said individual one of said samples, at at least one multiplicand of individual ones of said signal products being the complex conjugate of the sample from which said one multiplicand is derived, means (71-75) operative during each of said sampling periods for multiplying said products by respective associated coefficients to form a plurality of weighted products, the value of each of said coefficients during an individual one of said sampling being its value during a preceding sampling period modified by a correction factor, means (81-86) for combining said weighted products with each other to generate a feedforward nonlinear signal, means (11, 43) responsive to predetermined ones of said samples for generating a feedforward linear signal and for combining it with said feedforward nonlinear signal to form a composite feedforward signal, means (12) for demodulating said composite feedforward signal, means (17) for generating a quantized data signal in response to the demodulated composite feedforward signal, means for forming an error signal (20) in response to said demodulated signal and said quantized data signal, and means (28) for modulating said error signal at the carrier frequency of said modulated data signal to form a modulated error signal, said correction factor for an individual one of said coefficients being a function of the product associated with said individual one of said coefficients during said preceding sampling period and of the modulated error signal for said preceding sampling period.

Claim 32

In a method for equalizing complex samples of a received modulated data signal, said modulated data signal being of the type in which both the carrier phase and amplitude are modulated, that improvement which comprises the steps of forming a plurality of signal products associated with an individual one of said samples, each multiplicand of each product being derived from a respective one of said samples, each said respective one of said samples bearing a predetermined temporal relationship to said individual one of said samples, and at least one multiplicand of individual ones of said signal products being the complex conjugate of the sample from which said one multiplicand is derived, multiplying each of said products by an associated coefficient to form a plurality of weighted products, and combining said weighted products with each other to generate a feedforward nonlinear signal.

Claim 33

In a method for equalizing complex samples of a received modulated data signal, said modulated data signal being of the type in which both the carrier phase and amplitude are modulated, that improvement which comprises the steps of forming a plurality of signal products associated with an individual one of said samples, each multiplicand of each product being derived from a respective one of said samples, each said respective one of said samples bearing a predetermined temporal relationship to said individual one of said samples, and at least one multiplicand of individual ones of said signal products being the complex conjugate of the sample from which said one multiplicand is derived, multiplying each of said products by an associated coefficient to form a plurality of weighted products, and combining said weighted products with each other to generate a feedforward nonlinear signal.

Claim 34

In a method for equalizing complex samples of a received quadrature amplitude modulated data signal, that improvement which comprises the steps of forming a plurality of signal products associated with an individual one of said samples, each multiplicand of each product being derived from a respective one of said samples, each said respective one of said samples bearing a predetermined temporal relationship to said individual one of said samples, and at least one multiplicand of individual ones of said signal products being the complex conjugate of the sample from which said one multiplicand is derived, multiplying each of said products by an associated coefficient to form a plurality of weighted products, and combining said weighted products with each other to generate a feedforward nonlinear signal.

Claim 35

In a method for equalizing complex samples of a received quadrature amplitude modulated data signal, that improvement which comprises the steps of forming a plurality of signal products associated with an individual one of said samples, each multiplicand of each product being derived from a respective one of said samples, each said respective one of said samples bearing a predetermined temporal relationship to said individual one of said samples, and at least one multiplicand of individual ones of said signal products being the complex conjugate of the sample from which said one multiplicand is derived, multiplying each of said products by an associated coefficient to form a plurality of weighted products, and combining said weighted products with each other to generate a feedforward nonlinear signal.

Claim 36

The invention of claim 22 or claim 23 comprising the further steps of generating a feedforward linear signal in response to predetermined ones of said samples and combining said feedforward linear signal with said feedforward nonlinear signal to form a composite feedforward signal, and recovering the modulated data from said samples in response to said composite feedforward signal.

Claim 37

In a method for equalizing samples of a received modulated data signal in which both the carrier phase and amplitude are information-bearing, each of said samples being represented by a complex number, that improvement which comprises the steps of forming during each of a plurality of successive sampling periods a plurality of signal products associated with an individual one of said samples, each multiplicand of each product being derived from a respective one of said samples, each said respective one of said samples bearing a predetermined temporal relationship to said individual one of said samples, and at least one multiplicand of individual ones of said signal products being the complex conjugate of the sample from which said one multiplicand is derived, multiplying said products by respective associated coefficients during each of said sampling periods to form a plurality of weighted products, the value of each of said coefficients during an individual one of said sampling periods being its value during the preceding sampling period modified by a correction factor, combining said weighted products with each other to generate a feedforward nonlinear signal, generating a feedforward linear signal in response to predetermined ones of said samples and combining said feedforward linear signal with said feedforward nonlinear signal to form a composite feedforward signal, demodulating said composite feedforward signal, generating a quantized data signal in response to the demodulated composite feedforward signal, forming an error signal in response to said demodulated signal and said quantized data signal, and, modulating said error signal at the carrier frequency of said modulated data signal to form a modulated error signal, said correction factor for an individual one of said coefficients being a function of the product associated with said individual one of said coefficients during said preceding sampling period and of the modulated error signal for said preceding sampling period.

Claim 38

In a method for equalizing samples of a received modulated data signal in which both the carrier phase and amplitude are information-bearing, each of said samples being represented by a complex number, that improvement which comprises the steps of forming during each of a plurality of successive sampling periods a plurality of signal products associated with an individual one of said samples, each multiplicand of each product being derived from a respective one of said samples, each said respective one of said samples bearing a predetermined temporal relationship to said individual one of said samples, and at least one multiplicand of individual ones of said signal products being the complex conjugate of the sample from which said one multiplicand is derived, multiplying said products by respective associated coefficients during each of said sampling periods to form a plurality of weighted products, the value of each of said coefficients during an individual one of said sampling periods being its value during the preceding sampling period modified by a correction factor, combining said weighted products with each other to generate a feedforward nonlinear signal, generating a feedforward linear signal in response to predetermined ones of said samples and combining said feedforward linear signal with said feedforward nonlinear signal to form a composite feedforward signal, demodulating said composite feedforward signal, generating a quantized data signal in response to the demodulated composite feedforward signal, forming an error signal in response to said demodulated signal and said quantized data signal, and, modulating said error signal at the carrier frequency of said modulated data signal to form a modulated error signal, said correction factor for an individual one of said coefficients being a function of the product associated with said individual one of said coefficients during said preceding sampling period and of the modulated error signal for said preceding sampling period.