一种新的GMSK正交调制信号产生方法

A New Method for Generating the Quadrature GMSK Signal

提出了一种称为直接分解法的GMSK正交调制信号产生方法.将单个脉冲的高斯滤波器响应的积分相位轨迹分成暂态部分和稳态部分,并详细分析了这两部分的组成规律.暂态部分只与相邻的几个码元有关,状态有限,可制成表格,可用存储器来实现.稳态部分尽管与所有输入码元有关,但其三角函数值为±1,只引起暂态部分的符号变化,用简单的时序电路就可实现.设计了能用VLSI实现的正交GMSK调制方案.仿真实验结果证实这种方案可行,波形正确,频谱符合要求.

A new method for generating the quadrature GMSK signal,called Direct Decomposin g Modulation Phase(DDMP),is presented.The integrated phases of the Gaussian fil t ered 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 pa rt 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 dat a,the triangle function values of it are ±1,which only cause the sign of the t ransient part changing.A realization scheme for generation of I-Q GMSK signal i s designed.The simulating results validate the method,and the wave and the spec trum of the GMSK signal can be measured up to the GSM standard.