Amplitude modulation based on time-varying forced function of second-order oscillator circuit

This paper presents a novel technique of amplitude modulation which is based on a second-order oscillator circuit. By using the multi-time technique to analyze a second-order system for time-varying forced function, it is found that the system's forced response not only at an initial time but also at any arbitrary time is presented in term of the natural response's magnitude. It implies that amplitude of the natural response can directly be controlled by the forced response. For a condition that the forced response and the time-varying forced function is approximately identical, the resulted complete response of the second-order system therefore is amplitude modulation where the natural response and the time-varying forced function respectively represents sinusoidal carrier and information signals. To confirm the proposed technique, experimental results have been demonstrated which agree well with the given theoretical analysis.