Method and apparatus for high-speed data transfer employing self-synchronizing quadrature amplitude modulation

摘要

A Quadrature Amplitude Modulation (QAM) method and apparatus including a QAM transmit modulator with at least one unbalanced mixer, which creates an asymmetric two-dimensional (2-D) QAM symbol constellation. The asymmetrical symbol constellation provides baseband symbol clock signal leakage sufficient to facilitate quick and simple baseband symbol clock recovery and signal channel compensation at the QAM receiver without significantly degrading the system bit-error rate (BER). While slightly degrading static BER, overall system performance is improved when considering baseband symbol clock recovery and received signal compensation for an imperfect signal channel. This allows QAM to be deployed in systems where QAM is otherwise prohibitively expensive and improves overall system performance for any existing QAM system application without additional bandwidth, cost or complexity.

主权项

1. In a communication system including a data transmitter coupled through a signal channel to a data receiver, a method for transferring data through the signal channel comprising the steps of:
encoding the data to produce a first baseband modulating signal I(t) and a second baseband modulating signal Q(t) whose amplitudes together represent a time series of complex symbols (I, Q) each selected from a two-dimensional (2-D) constellation of symbols distributed on the phase plane about the origin such that at least one of the baseband modulating signals has a substantially non-zero mean amplitude; multiplying the first baseband modulating signal I(t) by a first baseband symbol clock signal to produce a first modulation product signal and multiplying the second baseband modulating signal Q(t) by a second baseband symbol clock signal to produce a second modulation product signal, where the phases of the first and second baseband symbol clock signals are generally fixed in quadrature; summing the first and second modulation product signals to produce a transmitter output signal; coupling the transmitter output signal through the signal channel to the data receiver; and demodulating the first and second modulation product signals at the data receiver to recover the series of complex symbols (I, Q).