Method for generating I/Q signal in a TDMA transmitter and corresponding modulator

A signal processing method for generating a digital in-phase/quadrature (I/Q) signal having a plurality of time-slots, the signal processing method comprising the steps of:

• under control of a modulator, generating a digital I/Q signal by,
• generating a first linearly modulated signal of a 0th order in an I/Q domain using a first pulse-shaping filter;
• generating a second linearly modulated signal of a higher order in the I/Q domain using a second pulse-shaping filter in a quadratic branch;
• and
• adding the first linearly modulated signal and the second linearly modulated signal to approximate a Gaussian Minimum Shift Keying (GMSK) modulator;
• and
• generating a dip in an envelope of the digital I/Q signal in a guard interval between adjacent time-slots of the plurality of time-slots by filling digital zeros into the first pulse-shaping filter and the second pulse-shaping filter.

A signal processing method, comprising:

• under control of a modulator,
• generating a digital in-phase/quadrature (I/Q) signal having a plurality of time-slots by selectively using a Gaussian Minimum Shift Keying (GMSK) modulation scheme when operating in a GMSK mode of operation and an 8Phase Shift Keying (8PSK) modulation scheme when operating in an 8PSK mode of operation, wherein the GMSK modulation scheme approximates a GMSK modulator to generate the digital I/Q signal by adding a series of at least two linearly modulated signals in an I/Q domain, wherein a first of the at least two linearly modulated signals is a 0th element of the series and is generated using a first pulse-shaping filter and a second of the at least two linearly modulated signals is a higher order element of the series and is generated using a second pulse-shaping filter, and wherein the 8PSK modulation scheme uses a 8PSK modulator to generate the digital I/Q signal, the 8PSK modulator including the first pulse-shaping filter;
• and
• generating a dip in an envelope of the digital I/Q signal in a guard interval between adjacent time-slots of the plurality of time-slots by filling digital zeros into at least one of the first pulse-shaping filter and the second pulse-shaping filter.

A transmitter, comprising:

• a modulator for generating a digital in-phase/quadrature (I/Q) signal having a plurality of time-slots, the modulator comprising:
• a first branch of 0th order with a first pulse-shaping filter for providing a first linearly modulated signal in an I/Q domain;
• at least one second branch of higher order with a second pulse-shaping filter for providing a second linearly modulated signal in the I/Q domain;
• an adder for adding the first linearly modulated signal and the second linearly modulated signal to approximate a Gaussian Minimum Shift Keying (GMSK) modulator;
• and
• means for introducing a dip in an envelope of the digital I/Q signal in a guard interval between adjacent time-slots of the plurality of time-slots, the means for introducing the dip in the envelope of the digital I/Q signal in the guard interval between the adjacent time-slots of the plurality of time-slots including means for filling digital zeros into the first pulse-shaping filter and the second pulse-shaping filter.