Title: Transmitter predistortion circuit and method therefor
Application Number: 200580009862 Application Date: 2005.01.24
Publication Number: 1938939 Publication Date: 2007.03.28
Approval Pub. Date: Granted Pub. Date:
International Classifi-cation: H03D3/24;H03H7/30
Applicant(s) Name: Crestcom Inc. Address:
Inventor(s) Name:
Attorney & Agent: yangkai chenjing jun
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 ).
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