Patent ID: 8081710

Claim:
An I/Q communication transmitter, comprising: a pre-distortion lookup table containing pre-distortion lookup data comprising predetermined amplitude correction coefficients and predetermined phase correction coefficients; an auto-calibration module in communication with the pre-distortion lookup table, and configured to operate during a closed-loop auto-calibration interval, said auto-calibration module configured to calibrate the pre-distortion lookup data to compensate for a non-linearity in the I/Q communication transmitter by generating and manipulating the predistortion lookup data exclusively in polar form; a baseband processor in communication with the pre-distortion lookup table and comprising the auto-calibration module, wherein the baseband processor is configured to receive an input signal in an I/Q form, convert said input signal from said I/Q form to a polar form so as to obtain an input magnitude signal and an input phase signal, use said input magnitude signal and said input phase signal to determine locations within said pre-distortion lookup table for a first amplitude correction coefficient of said predetermined amplitude correction coefficients and a first phase correction coefficient of said predetermined phase correction coefficients necessary for proper pre-distortion of said input signal, and generate a pre-distorted baseband I/Q signal pair by performing pre-distortion operations exclusively in a polar domain, and wherein the pre-distortion is based on the first amplitude correction coefficient and the first phase correction coefficient during an open-loop operational interval; an I/Q modulator in communication with the baseband processor, wherein the I/Q modulator is configured to modulate an RF carrier signal based on the pre-distorted baseband I/Q signal pair and to generate a pre-distorted, modulated RF carrier signal by performing modulation operations in an I/Q domain; a power amplifier in communication with the baseband processor and the I/Q modulator, wherein the power amplifier is configured to amplify the pre-distorted, modulated RF carrier signal and to generate an amplified RF signal; a digital feedback path in communication with the power amplifier and the baseband processor, wherein the digital feedback path is configured to process the amplified RF signal to generate a polar feedback signal in a polar form and to provide the polar feedback signal to the baseband processor during the closed-loop auto-calibration interval; wherein the baseband processor is further configured to perform the following operations for updating the pre-distortion look-up data during the closed-loop auto-calibration interval: generate a polar input signal by converting the input signal from the I/Q form to a polar form; collect data regarding a nonlinear relationship between the polar feedback signal and the polar input signal; and store the data in the pre-distortion lookup table for use during the open-loop operational interval.