Constrained-envelope digital-communications transmission system and method therefor

In a digital communications system, a method for the transmission of a constrained-envelope communications signal, said transmission method comprising the steps of:

• filtering a quadrature phase-point signal stream to produce a filtered signal stream, said filtering step spreading energy from each phase point in said filtered signal stream over a plurality of unit baud intervals;
• generating a constrained-bandwidth error signal stream from said filtered signal stream and a threshold signal;
• combining said filtered signal stream and said constrained-bandwidth error signal stream to produce a constrained-envelope signal stream;
• linearly amplifying said constrained-envelope signal stream to produce said constrained-envelope communications signal;
• and
• transmitting said constrained-envelope communications signal.

A constrained-envelope digital-communications transmitter circuit comprising:

• a binary data source configured to provide a binary input signal stream;
• a phase mapper coupled to said binary data source and configured to produce a quadrature phase-point signal stream, wherein said phase-point signal stream has a predetermined number of symbols per unit baud interval, said predetermined number of symbols defining a phase point in a phase-point constellation;
• a Nyquist-type filter coupled to said phase mapper and configured to produce a filtered signal stream;
• a constrained-envelope generator coupled to said Nyquist-type filter and configured to produce a constrained-bandwidth error signal stream;
• a delay element coupled to said Nyquist-type filter and configured to produce a delayed signal stream synchronized with said constrained-bandwidth error signal stream;
• a complex summing circuit coupled to said delay element and said constrained-envelope generator and configured to produce a constrained-envelope signal stream;
• and
• a substantially linear amplifier coupled to said complex summing circuit and configured to produce a radio-frequency broadcast signal.