Abstract

Digital signals are converted to phase and amplitude altered, periodic, analog signals and emplaced on an output link. The system is adaptive and includes a plurality of simple quadrature phase shift keying modulators, each modulator having a plurality of controlling digital inputs, the states of which determine which of a plurality of phase displaced signals will be outputted. A local oscillator provides a periodic sinusoidal signal to each QPSK modulator. Summing circuits combine the outputs of the modulators so as to produce a constellation of phase and amplitude-displaced output sinusoidal signals. A processor/mapper combination enables conversion of a first set of digital inputs to a different set of digital outputs in accordance with a control input. Thus, the processor enables the alteration of the constellation of outputs in accordance with a control input, which may be indicative of the condition of a transmission facility.