Abstract: The linear scattering parameter can not represent and design the nonlinear microwave circuit accurately. The definition of nonlinear scattering function can be introduced similar to the linear network parameter. The theoretical system of the nonlinear scattering function has been built based on the conclusions of their linearization, definition and characteristic. The nonlinear network measurement system based on the digital oscilloscope is built. To the microwave transistor, amplitude and phase of incident and reflected waves can be obtained. The nonlinear scattering function can be extracted from the measuremental result, and the experimental results conform to the rule for the nonlinear microwave circuit. This theory can be used as a new tool to character the nonlinear microwave circuit.

Key words: microwave nonlinear circuit, nonlinear scattering function, large signal network measurement system