An experimental investigation of GMSK modulation

This paper presents the experimental circuit used to generate GMSK modulated signals within a time frame. GMSK signal is represented as a 12PM3 continuous phase frequency shift keying modulation. A Quadrature modulator is implemented by using lookup tables of cos(/spl phi/(t;I)) and sin(/spl phi/(t;I)) values. EPROMs are used to store phase, sine and cosine information contained in lookup tables. Satisfactory outputs are obtained for the modulated signals with premodulation lowpass filter values BT=/spl infin/, BT=0.315.