Patent ID: 6771711
Filing Date: 2004-08-03
Classification: H03M,H04L

Abstract:
A digital Gaussian minimum shift keying (GMSK) filter for frequency modulating a carrier signal in a GMSK transmission system, the GMSK filter comprising:a control logic module having a shift register receiving modulation bits, said shift register having a first side for receiving logic 1 values of the modulation bits and a second side receiving logic 0 values of the modulation bits, said second side being opposite said first side, said shift register having a shift direction switchable between a stop, a left and a right shift direction; a number of individual current sources outputting individual current values with said individual current sources being individually driven by said control logic module in accordance with a digital signal to be modulated; and an output resistor coupled to said individual current sources with a total current from said individual current sources being converted by said output resistor to a voltage value for controlling a voltage controlled oscillator, by which a frequency of the carrier signal is modulated.