Reduction of average-to-minimum power ratio in communications signals

1. A method of reducing the average-to-minimum magnitude ratio (AMR) of a communications signal having a sequence of symbols, comprising:

obtaining a digital message for generating the communications signal having a sequence of symbols;

applying a pulse-shaping technique to an instance of a pulse of a given form to generate a communications signal s(t);

obtaining a minimum value ρ(t min ) of the magnitude of the generated communication signal s(t) at a time instant t_min in a time interval between two distinct time instants t1 and t2 (t 1 <t 2 );

generating, in the time interval between the time instants t 1 and t 2 , a correction signal with a predetermined impulse response r(t−t min ) which is obtained based on the minimum value and the predetermined signal envelope minimum if it is determined that ρ(t min ) is smaller than a predetermined signal envelope minimum; and

adding the correction signal to the communications signal to generate a modified communications signal, wherein

the communications signal is represented within a signal plane having an origin denoting a signal of zero magnitude;

the minimum value of the magnitude of the communications signal is calculated from a distance from the origin to a first straight line spanning a coordinate of the communications signal s(t 1 ) and a coordinate of the communications signal s(t 2 ), and the method further comprises:

determining the first straight line spanning the coordinate of the communications signal s(t 1 ) and the coordinate of the communications signal s(t 2 ) and a second straight line passing through the origin and being orthogonal to the first straight line; and

calculating the minimum value ρ(t min ) of the magnitude of the communications signal from a distance from the origin to an intersection point of the first straight line and the second straight line.

2. The method of claim 1 wherein the correction signal is added to the communications signal at times other than t=kT+T/2, where T denotes the symbol period and k is an integer.

3. The method of claim 1 , wherein a correction weight C is determined based on the minimum value and the predetermined signal envelope minimum; and

the predetermined impulse response r(t−t min ) is generated based on the correction weight C.

4. The method of claim 1 , wherein

the communications signal s(t 1 ) and the communications signal s(t 2 ) are generated by using a pulse-shaping filter p(t), and

the pulse-shaping filter p(t) and a pulse-shaping filter r(t) having the correction weight C are substantially identical to each other.

5. The method of claim 1 , wherein

a modified in-phase component, which the modified communications signal has, is translated to an amplitude component and a phase component and a modified quadrature component, which the modified communications signal has, is translated to an amplitude component and a phase component, and the amplitude components and the phase components are polar-modulated.

6. The method of claim 1 , wherein the minimum value ρ(t min ) is generated using a locally-linear model.

7. A PAM generator, comprising:

a baseband modulator for applying a pulse-shaping technique to instance of a pulse of a given form to generate a communications signal;

an analyzer connected to an output end of the baseband modulator for obtaining a minimum value ρ(t min ) of the magnitude of the communications signal at a time instant t min in a time interval between two distinct time instants t 1 and t 2 (t 1 <t 2 );

a pulse-shaping filter connected to an output end of the analyzer for generating, in the time interval between the time instants t 1 and t 2 , a correction signal by multiplying a correction weight C, based on the minimum value ρ(t min ) and a predetermined signal envelope minimum, by a predetermined impulse response r(t−t min ), which is based on the time instant t min , if it is determined that there exists a time instant tin the time interval between the time instants t 1 and t 2 where the magnitude of the communications signal at the time instant t is smaller than the predetermined signal envelope minimum; and

an adder for adding the correction signal to the communications signal s(t) to generate a modified communications signal, wherein

the communications signal is represented within a signal plane having an origin denoting a signal of zero magnitude;

the minimum value ρ(t min ) of the magnitude of the communications signal is calculated from a distance from the origin to a first straight line spanning a coordinate of the communications signal s(t 1 ) and a coordinate of the communications signal s(t 2 );

the first straight line spanning the coordinate of the communications signal s(t 1 ) and the coordinate of the communications signal s(t 2 ), and a second straight line passing through the origin and being orthogonal to the first straight line are determined; and

the minimum value ρ(t min ) of the magnitude of the communications signal from a distance from the origin to an intersection point of the first straight line and the second straight line is calculated.

8. The PAM generator according to claim 7 , wherein

the communications signal s(t 1 ) and the communications signal s(t 2 ) are generated by using a pulse-shaping filter p(t), and

the pulse-shaping filter p(t) and a pulse-shaping filter r(t) having the correction weight C are substantially identical with each other.

9. The PAM generator according to claim 7 further comprising

a coordinate translation section, wherein

the coordinate translation section translates a modified in-phase component of the modified communications signal to an amplitude component and a phase component, translates a modified quadrature component of the modified communications signal to an amplitude component and a phase-component, and polar-modulates the phase components and the phase-components.