New method for generating the quadrature GMSK signal

A new method for generating the quadrature GMSK signal, called Direct Decomposing Modulation Phase (DDMP), is presented. The integrated phases of the Gaussian filtered pulse response are turned into two parts: the transient part and the stable part, and the construction of the two parts are analyzed in detail. The transient part is relative only to several near input data bits, its states being finite, which means the transient part can be made into a table to be stored into a EPROM. Although the stable part is relative to the history of all the input data, the triangle function values of it are ±1, which only cause the sign of the transient part changing. A realization scheme for generation of I-Q GMSK signal is designed. The simulating results validate the method, and the wave and the spectrum of the GMSK signal can be measured up to the GSM standard.