Abstract: A digital communications transmitter (100) includes a digital linear-and-nonlinear predistortion section (200) to compensate for linear and nonlinear distortion introduced by transmitter-analog components (120). A direct-digital-downconversion section (300) generates a complex digital return-data stream (254) from the analog components (120) without introducing quadrature imbalance. A relatively low resolution exhibited by the return-data stream (254) is effectively increased through arithmetic processing. Linear distortion is first compensated using adaptive techniques with an equalizer (246) positioned in the forward-data stream (112). Nonlinear distortion is then compensated using adaptive techniques with a plurality of equalizers (226) that filter a plurality of orthogonal, higher-ordered-basis functions (214) generated from the forward-data stream (112). The filtered-basis functions are combined together and subtracted from the forward-data stream (112).

Abstract: A digital communications transmitter (100) includes a digital linear-and-nonlinear predistortion section (200) to compensate for linear and nonlinear distortion introduced by transmitter-analog components (120). A direct-digital-downconversion section (300) generates a complex digital return-data stream (254) from the analog components (120) without introducing quadrature imbalance. A relatively low resolution exhibited by the return-data stream (254) is effectively increased through arithmetic processing. Linear distortion is first compensated using adaptive techniques with an equalizer (246) positioned in the forward-data stream (112). Nonlinear distortion is then compensated using adaptive techniques with a plurality of equalizers (226) that filter a plurality of orthogonal, higher-ordered-basis functions (214) generated from the forward-data stream (112). The filtered-basis functions are combined together and subtracted from the forward-data stream (112).

Abstract: A digital communication transmitter serves as a signal path (10) which uses an adaptive equalizer (18) in a predistortion role. The adaptive equalizer (18) pre-distorts a complex digital communication signal (12) that need not exhibit any distortion. Subsequent analog distortion-introducing segments (24, 30, 36, 42) then distort a predistorted signal (22) output from the adaptive equalizer (18). An error signal (46) is formed from a reference signal (52) and a return signal (54). The equalizer (18) implements an adaptation algorithm that adjusts filter (68) coefficients to minimize correlation between one of the reference and return signals (52, 54) and the error signal (46). The equalizer (18) generates four sets of coefficients for four different filters. Consequently, the equalizer (18) exhibits four degrees of freedom in introducing predistortion into a complex signal to counter the distortion subsequently introduced in the signal path (10) by the distortion-introducing segments (24, 30, 36, 42).

Abstract: A digital communications transmitter (100) includes a digital linear-and-nonlinear predistortion section (200) to compensate for linear and nonlinear distortion introduced by transmitter-analog components (120). A direct-digital-downconversion section (300) generates a complex digital return-data stream (254) from the analog components (120) without introducing quadrature imbalance. A relatively low resolution exhibited by the return-data stream (254) is effectively increased through arithmetic processing. Linear distortion is first compensated using adaptive techniques with an equalizer (246) positioned in the forward-data stream (112). Nonlinear distortion is then compensated using adaptive techniques with a plurality of equalizers (226) that filter a plurality of orthogonal, higher-ordered-basis functions (214) generated from the forward-data stream (112). The filtered-basis functions are combined together and subtracted from the forward-data stream (112).

Abstract: A digital communication transmitter serves as a signal path (10) which uses an adaptive equalizer (18) in a predistortion role. The adaptive equalizer (18) pre-distorts a complex digital communication signal (12) that need not exhibit any distortion. Subsequent analog distortion-introducing segments (24, 30, 36, 42) then distort a predistorted signal (22) output from the adaptive equalizer (18). An error signal (46) is formed from a reference signal (52) and a return signal (54). The equalizer (18) implements an adaptation algorithm that adjusts filter (68) coefficients to minimize correlation between one of the reference and return signals (52, 54) and the error signal (46). The equalizer (18) generates four sets of coefficients for four different filters. Consequently, the equalizer (18) exhibits four degrees of freedom in introducing predistortion into a complex signal to counter the distortion subsequently introduced in the signal path (10) by the distortion-introducing segments (24, 30, 36, 42).