US Patent 7724840 RF transmitter with predistortion and method therefor

An RF transmitter (10) includes a linear predistorter (22) and a nonlinear predistorter (24) which together drive analog transmitter components (14). The linear and nonlinear predistorters (22, 24) are implemented using a collection of adaptive equalizers (30). A feedback signal (20) is developed by downconverting an RF communication signal (16) obtained from the analog components (14). The feedback signal (20) are used in driving tap coefficients (34) for the adaptive equalizers (30′, 30″) in the nonlinear predistorter (24). An intermodulation-product canceller (94) uses signal cancellation to cancel intermodulation products from the feedback signal (20) and generate an intermodulation-neutralized feedback signal (96). The intermodulation-neutralized feedback signal (96) is used along with a modulated convergence factor (43) in driving tap coefficients (34) for the adaptive equalizer (30) in the linear predistorter (22).