A Method for Obtaining Constant Envelope Quadrature Modulation System Base-Band Signal

In this article a new method based on the function sinn(πt/2Tb) is proposed to obtain 2Tb-long base-band signal which can be applied to quadrature modulation to make the modulated signal constant-enveloped and phase-continuous. The power spectrum of the signal attenuates more quickly and the out-of-band radiation decreases. The general expression of the signal is given and the time-frequency property has been analyzed. We established the modulation-demodulation model and realized the modulation and demodulation process by using MATLAB. Bit error rate characteristic has been analyzed and the simulation results proved the validity of this method.