1. A method for stabilizing a coefficient set used by a digital predistortion (DPD) engine to apply pre-distortion to a transmit signal and cancel distortion generated by a distorting element or distorting system when transmitting the transmit signal, the method comprising: obtaining an initial coefficient set; rotating the initial coefficient set to maintain a phase of fundamental components (w 10 (t),. .. , w 1Q (t)) of the initial coefficient set as a constant value; averaging in the time domain the rotated coefficient set to obtain an averaged coefficient set; applying the averaged coefficient set to the DPD engine, the initial coefficient set expressed as W ⁡ ( t ) = [ w 10 ⁡ ( t ) w 11 ⁡ ( t ) … w 1 ⁢ Q ⁡ ( t ) w 20 ⁡ ( t ) w 21 ⁡ ( t ) … w 2 ⁢ Q ⁡ ( t ) … … … … w K ⁢ ⁢ 0 ⁡ ( t ) w K ⁢ ⁢ 1 ⁡ ( t ) … w KQ ⁡ ( t ) ] ; computing the phase of the fundamental components of the initial coefficient set as θ 1 ⁡ ( t ) = angle ⁡ ( ∑ q = 0 Q ⁢ w 1 ⁢ q ⁡ ( t ) ) ; and computing the rotated coefficient set as W 2 ⁡ ( t ) = [ w 10 ⁡ ( t ) w 11 ⁡ ( t ) … w 1 ⁢ Q ⁡ ( t ) w 20 ⁡ ( t ) w 21 ⁡ ( t ) … w 2 ⁢ Q ⁡ ( t ) … … … … w K ⁢ ⁢ 0 ⁡ ( t ) w K ⁢ ⁢ 1 ⁡ ( t ) … w KQ ⁡ ( t ) ] ⁢ ⅇ - jθ 1 ⁡ ( t ) .