Equivalent baseband analysis of narrow weakly nonlinear bandpass systems for waveform diversity applications

Because electronic components are inherently nonlinear, actual circuits implemented for waveform diversity applications experience nonlinear effects that can severely degrade performance. For systems intended to operate in a linear fashion, a weakly nonlinear model is appropriate. In principle, computer simulations can be used to determine the waveform distortion caused by the nonlinear behavior. However, in general, when waveform diversity applications involve modulated signals with large carrier frequencies, extremely high sampling frequencies are required. This paper develops an equivalent baseband baseband analysis that enables the distorted output modulations to be determined using much lower baseband sampling frequencies. The method is illustrated with an example involving two amplitude modulated signals at the input to a bandpass system having a third-order nonlinearity.