Apparatus and method for modulating and digitally predistorting a signal in a multiple modulation schemes

A programmable modulator ( 100 ) is programmable to operate in either of a GMSK or 8PSK mode. When operating in a GMSK mode, a signal modulating circuit 105 receives ( 210 ) a bit stream ( 110 ), maps the bit stream ( 110 ) to a phase value in complex I, Q form and applies a progressive rotation to...

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Bibliographische Detailangaben
Hauptverfasser:	NASH GREGORY T, AMAN ASAD U, KUNDMANN THOMAS J
Format:	Patent
Sprache:	eng
Schlagworte:	AMPLIFIERS BASIC ELECTRONIC CIRCUITRY ELECTRIC COMMUNICATION TECHNIQUE ELECTRICITY JAMMING OF COMMUNICATION SECRET COMMUNICATION TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHICCOMMUNICATION WIRELESS COMMUNICATIONS NETWORKS
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Beschreibung
Zusammenfassung:	A programmable modulator ( 100 ) is programmable to operate in either of a GMSK or 8PSK mode. When operating in a GMSK mode, a signal modulating circuit 105 receives ( 210 ) a bit stream ( 110 ), maps the bit stream ( 110 ) to a phase value in complex I, Q form and applies a progressive rotation to the phase value according to GMSK specifications. The output ( 140 ) is filtered by a filter circuit ( 135 ), preferably using a complex Finite Impulse Response (FIR) filter using the standard coefficients for an 8PSK modulation to create ( 215 ) an approximate GMSK output ( 165 ). A GMSK correction circuit ( 150 ) determines a correction term that is added to the filter circuit output ( 165 ) so as to correct amplitude variations to allow the output to conform to GSM/EDGE standards. The same modulator ( 100 ) may be programmed to operate in an 8PSK mode with linear predistortion.