Reduction of average-to-minimum power ratio in communications signals
First Claim
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1. A method of altering a communications signal to reduce an average-to-minimum power ratio thereof, the communications signal being formed using pulse-shaping techniques applied to instances of a pulse of a given form, the communication signal using constellation points, the method comprising, for at least one signal component:
- setting a desired signal envelope minimum;
mapping a digital stream of bits onto a symbol constellation to generate a sequence of symbols;
generating signal sample points from the sequence of symbols;
identifying two or more signal sample points between which a communications signal is likely to reach a local envelope minimum;
using a mathematical model of the communications signal, the two or more signal sample points lying in between two constellation points;
determining a minimum of the communications signal envelope between the signal sample points and a time at which the minimum between the signal sample points occurs;
determining a measure of at least one of magnitude and phase of the communications signal corresponding to the minimum of the communications signal; and
if said minimum of the communications signal is less than the desired signal minimum;
in accordance with said one of magnitude and phase, forming a scaled corrective pulse; and
adding to the signal component the scaled corrective pulse, in timed relation to the signal, to form a modified communications signal having a reduced average-to-minimum power ratio.
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Abstract
This invention, generally speaking, modifies pulse amplitude modulated signals to reduce the ratio of average power to minimum power. The signal is modified in such a manner that the signal quality remains acceptable. The signal quality is described in terms of the Power Spectral Density (PSD) and the Error Vector Magnitude (EVM).
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Citations
22 Claims
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1. A method of altering a communications signal to reduce an average-to-minimum power ratio thereof, the communications signal being formed using pulse-shaping techniques applied to instances of a pulse of a given form, the communication signal using constellation points, the method comprising, for at least one signal component:
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setting a desired signal envelope minimum; mapping a digital stream of bits onto a symbol constellation to generate a sequence of symbols; generating signal sample points from the sequence of symbols; identifying two or more signal sample points between which a communications signal is likely to reach a local envelope minimum; using a mathematical model of the communications signal, the two or more signal sample points lying in between two constellation points;
determining a minimum of the communications signal envelope between the signal sample points and a time at which the minimum between the signal sample points occurs;determining a measure of at least one of magnitude and phase of the communications signal corresponding to the minimum of the communications signal; and if said minimum of the communications signal is less than the desired signal minimum; in accordance with said one of magnitude and phase, forming a scaled corrective pulse; and adding to the signal component the scaled corrective pulse, in timed relation to the signal, to form a modified communications signal having a reduced average-to-minimum power ratio. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 18, 19, 20)
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15. A method of altering a communications signal to reduce an average-to-minimum power ratio thereof, the communications signal being represented in polar form having a magnitude component and a phase-related component, the communication signal using constellation points, the method comprising, for at least one signal component:
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filtering a communications signal using a nonlinear filter in a polar domain; setting a desired signal envelope minimum; identifying a time instant between two samples at which the signal envelope falls below the desired signal envelope minimum, the two samples lying in between two constellation points; and adding to the signal component a corrective pulse, in timed relation to the signal, to form a modified communications signal having a reduced average-to-minimum power ratio. - View Dependent Claims (16, 17)
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21. A method of conditioning a communications signal, comprising:
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assigning mathematical coordinates to two signal samples of a communications signal, the communication signal comprising a plurality of constellation points, said two signal samples lying between two constellation points, said two signal samples being in the temporal vicinity of a low-magnitude event of the communications signal; calculating a minimum magnitude of the communications signal using the mathematical coordinates; if the calculated minimum magnitude is less than a predetermined threshold, forming a correction pulse; and combining the correction pulse coherently with the communications signal in the temporal vicinity of the low-magnitude event.
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22. A method of conditioning a communications signal, comprising:
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determining in a coordinate system, a spatial orientation of at least two samples related to a communications signal, the communication signal associated with at least two constellation points, the at least two samples lying between two constellation points; determining a minimum threshold of the communications signal in the coordinate system; using the coordinates of the at least two samples, determining if the communications signal encounters a threshold event, wherein the communications signal will fall below the minimum threshold; based upon if the communications signal falls below the minimum threshold; forming a correction pulse; and combining the correction pulse with the communications signal in the temporal vicinity of the threshold event.
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Specification