Rapid scan Fourier transform spectroscopy was used to study the high frequency dynamic properties of the two dimensional electron gases (2DEG) confined at the interface of heterojunctions or in a quantum well. By using a multi channel voltage supply unit controlled by the spectrometer and accumulating alternately a certain number of scans at two different gate voltages, gate voltage ratio spectra were obtained on samples prepared with metallic front gates. Several fundamental infrared excitations, namely, cyclotron resonance, 2D plasmon and the collective intersubband resonance were observed in these low dimensional systems.