Power reduction
View Patent ↗There is disclosed a technique in which any peaks above a threshold level are reduced, but not clipped, such that the effects of such peaks is reduced. Although the implementation of the technique preferably includes a clipping step, it is performed on the front-end rather than as the last step in the technique, such that the output signal is not a clipped signal. Any noise introduced by the clipping step, so-called clipping noise, is preferably filtered out of the useful frequency band of the signal.
1. A method of processing a band-limited, over-sampled signal comprising: clipping the band-limited, over-sampled signal at a given threshold; subtracting the clipped signal from the band-limited, over-sampled signal; filtering the subtracted signal to thereby control the frequency position of a clipping noise; delaying the band-limited, over-sampled signal; and subtracting the filtered clipped signal from the delayed band-limited, over-sampled signal, thereby reducing the amplitude of those portions of the band-limited, over-sampled signal having peaks above the given threshold.
2. The method of claim 1 wherein the step of filtering the subtracted signal comprises creating a pulse having a pre-determined shape dependent upon samples of the clipped signal.
3. The method of claim 1 wherein the step of delaying comprises delaying the band-limited, over-sampled signal by an amount corresponding to the time taken to implement the clipping and filtering steps.
4. The method of claim 1 further comprising a step of controlling the frequency position of the noise comprises moving the noise outside the frequency band used by the signal.
5. The method of claim 1 further comprising a step of controlling the frequency position of the noise comprises moving the noise outside the frequency band used by a signal transmitted in an opposite direction.
6. The method of claim 5 wherein the band-limited, over-sampled signal contributes an echo to the band-limited, over-sampled signal transmitted in an opposite direction.
7. A method of processing a band-limited, over-sampled signal comprising the steps of:
(a) reducing the amplitude of those portions of the band-limited, over-sampled signal having peaks above a threshold value;
(b) clipping the band-limited, over-sampled signal relative to the threshold,
wherein the step of clipping the band-limited, over-sampled signal further comprises limiting the amplitude of the band-limited, over-sampled signal to the threshold, and
subtracting the limited amplitude signal from the band-limited, over-sampled signal;
(c) filtering the clipped signal;
(d) combining the filtered clipped signal with the band-limited, over-sampled signal; and
(e) controlling the frequency position of the noise associated with the reduction of such peaks.
8. The method of claim 7 , wherein the step of filtering the clipped signal comprises creating a pulse having a pre-determined shape dependent upon samples of the clipped signal.
9. The method of claim 7 , wherein the step of combining comprises subtracting the filtered clipped signal from the band-limited, over-sampled signal.
10. The method of claim 7 , wherein the step of combining comprises delaying the band-limited, over-sampled signal by an amount corresponding to the time taken to implement the clipping and filtering steps.
11. The method of claim 7 , wherein the step of controlling the frequency position of the noise comprises filtering.
12. The method of claim 7 , wherein the step of controlling the frequency position of the noise comprises moving the noise outside the frequency band used by the band-limited, over-sampled signal.
13. The method of claim 7 , wherein the step of controlling the frequency position of the noise comprises moving the noise outside the frequency band used by a signal transmitted in an opposite direction.
14. The method of claim 13 , wherein the band-limited, over-sampled signal contributes an echo to the signal transmitted in an opposite direction.