1. A non-transitory computer-readable medium that, when executed by a processor, configures the processor to characterize a nonlinear system, by performing the steps of: applying a first signal to the nonlinear system; determining a first response of the nonlinear system to the first signal; applying a second signal to the nonlinear system; determining a second response of the nonlinear system to the second signal; and performing a mathematical operation based on the first signal, the second signal, the first response, and the second response to generate an output that characterizes the nonlinear system.