Patent ID: 6973141

Claim:
A method of baseband digital modulation for a data transmission system wherein a plurality of data symbols is transmitted over a transmission channel at a symbol rate; said method comprising the steps of: generating a plurality of inphase (I) and quadrature (Q) components of symbols by mapping an input bit stream comprising a plurality of digital codewords into a QAM constellation; bandlimiting, quantizing, interpolating, and pre-compensating said I and Q components a digital signal for a sinc (sin x/x) function amplitude roll off by utilizing a Polyphase filter at a baseband frequency; converting a plurality of digital symbols into an analog signal by using a D/A converter in each I and Q channels separately; prefiltering by a lowpass analog antialiasing prefilter an I analog signal in an I channel, and an Q analog signal in a Q channel separately; and complexly combining said I component and said Q component of said analog signal by an (I/Q) modulator to generate a real analog RF signal at an interpolated sampling rate.