Patent ID: 8908797

Claim:
A method for performing Time Alignment (TA) for an Envelope Tracking (ET) Radio Frequency (RF) Power Amplifier (PA) having an input signal, including a complex signal, that is propagated along a forward path of the ET RF PA having a forward path delay, a reference signal that is propagated along a zero-delay reference path of the ET RF PA, and a feedback signal, extracted from an output node of the ET RF PA, propagating along a feedback path having a feedback path delay, the method comprising: generating samples of the reference signal and the feedback signal at a sampling rate of 1/N to generate a captured sequence of data having a length of N samples, N being a value greater than or equal to one; calculating a cross-covariance of the feedback signal and the reference signal according to the captured sequence of data in order to generate a cross-covariance vector; determining peak values and corresponding index values of the N samples of the cross-covariance vector; determining a loop peak index and an envelope peak index; determining a delay difference between the envelope peak index and the loop peak index; determining an envelope delay and a loop delay respectively according to the envelope peak index and the loop peak index; performing a fine time delay estimation in order to generate a fractional envelope delay and a fractional loop delay respectively according to the envelope peak index and the loop peak index; and generating time delay settings according to the delay difference, the loop delay, the envelope delay, the fractional loop delay, and the fractional envelope delay, wherein the time delay settings include a coarse reference delay, a coarse forward delay, the fractional envelope delay and a fractional feedback delay.