When viewed as a Taylor series expansion such as Eq. (6.18), the simplest nonlinearity is clearly the square law nonlinearity:
where is a parameter of the mapping.7.18
Consider a simple signal processing system consisting only of the square-law nonlinearity:
The Fourier transform of the output signal is easily found using the dual of the convolution theorem: 7.19
where `` '' denotes convolution. In general, the bandwidth of is double that of .