According to the time-varying circuit concept

signal and circuitry system theory

we establish a time-varying linear circuit model of two-diode sampler using Nose-To-Nose(NTN) calibration procedure in this paper

and derive expressions of kick-out pulse and the impulse response of the sampler in time domain

proving that kick-out pulse is a natural response of the sampling circuit in the NTN.A new data-processing method is presented to obtain the varying RC parameter from the kick-out pulses acquired for the determination of the impulse response of sampler of oscilloscope.The problem of diode junction capacitance effect on the NTN calibration can be solved.