In an example, an apparatus for signal classification in a digital pre-distortion (DPD) system includes a positive frequency path including a first half-band low pass filter (LPF) operable to filter samples of an input digital samples after positive frequency translation; a negative frequency path including a second half-band LPF operable to filter the samples of the input digital samples after negative frequency translation; a power estimation circuit coupled to the positive frequency path and the negative frequency path, the power estimation circuit operable to determine a first average power based on output of the first half-band LPF, a second average power based on output of the second half-band LPF, and a total average power of the input digital samples; and a controller operable to determine a frequency content metric from the first average power and the second average power, and to select a set of filter coefficients for the DPD system based on the frequency content metric and the total average power.