Patent ID: 7349487

Claim:
A communication system comprising: a first communication device including: a digital signal source; a quadrature amplitude modulation unit operatively coupled to the digital signal source; a first pulse shaping filter operatively coupled to the quadrature amplitude modulation unit, wherein the first pulse shaping filter is such that the frequency domain response meets the Nyquist criteria and that the square root of the frequency domain response has a first derivative that is continuous at all points, the pulse shaping filter having an impulse response corresponding to the square root of the frequency domain response; a modulator operatively coupled to receive a signal from the pulse shaping filter; and a transmitter operatively coupled to the modulator; and a second communication device including a receiver; a demodulator operatively coupled to the receiver; a second pulse shaping filter, the second pulse shaping filter being matched to the first pulse shaping filter and being such that the frequency domain response meets the Nyquist criteria and that the square root of the frequency domain response has a first derivative that is continuous at all points, the second pulse shaping filter having an impulse response corresponding to the square root of the frequency domain response; a quadrature amplitude demodulation unit operatively coupled to the second pulse shaping filter; and a signal output operatively coupled to the quadrature amplitude demodulation unit.