Patent ID: 6025758
Filing Date: 2000-02-15
Classification: H04L

Abstract:
A method for generating at least one GMSK modulating signal from a serial digital data bit stream in order that the at least one GMSK modulating signal may modulate a carrier frequency signal associated with a GMSK transmitter of a digital communications system, the method comprising the steps of:a) converting each set of m consecutive data bits of the serial digital data bit stream into a parallel symbol, there being 2.sup.m possible symbols, each symbol being generally defined as (B.sub.-(m-1), . . . B.sub.0), where B.sub.0 is a current data bit and B.sub.-(m-1) is an mth previous data bit with respect to B.sub.0 ;b) assigning a corresponding phase advance to each of the 2.sup.m symbols, each phase advance being substantially equivalent to a percent phase advance contributed by m consecutive data bits of each symbol;c) assigning at least four corresponding accumulated phases to each of the 2.sup.m symbols, each of the at least four accumulated phases being derived from a multiple of 90 degrees;d) storing a plurality of digitally represented waveform portions in a memory unit, each one of a plurality of waveform portions respectively representing a time varying waveform that advances in phase by an amount respectively equal to each one of the at least four accumulated phases assigned to each of the 2.sup.m symbols;e) adding the phase advance assigned to a current symbol to the phase advance accumulated from a previous symbol in order to yield a current accumulated phase for the current symbol;f searching the memory unit for the digitally represented waveform portion that corresponds to a current accumulated phase for the current symbol;g) outputting the digitally represented waveform portion that corresponds to a current accumulated phase from the memory unit; andh) performing steps e) through g) for each data bit of a digital data bit stream to form a digital representation of the at least one GMSK modulating signal.