  In this paper, frequency-domain analysis based on frequency sweep method is
presented for a nonlinear double integrator and a new linear integrator. All
the two types of integrators can estimate the onefold and double integrals of a
signal synchronously. With respect to the linear double integrator, the
nonlinear integrator has better estimation performance and stronger robustness.
Importantly, the integrator parameters can be regulated from the
frequency-domain analysis.
