Shaping filter for high data rate signalling

Details Shaping filter for high data rate signalling Shaping filter for high data rate signalling

1997-03-03

1999-02-02

Bocure, Tesfaldet

Pulse or digital communications

Pulse code modulation

375295, H04B 1404

Patent

active

058675299

ABSTRACT:
A shaping filter for a PAM mapper is provided which manipulates incoming PAM code level signals to produce outgoing PAM code level signals whose frequency spectrum is shaped to meet desired criteria. In manipulating input code level values in(t), the shaping filter preferably utilizes previous output signal values without using previous incoming signal values. In a preferred embodiment, the output code level values out(t) are constrained to an output alphabet which is a predefined subset of code levels within the .mu.-law constellation, and are obtained by manipulating the input signals according to an integer-valued shifting function such that out(t) are code level values within the output alphabet. The preferred shifting function S "shifts" in(t) by a number of places in the output alphabet in the direction opposite the sign of ##EQU1## to provide out(t), where out(t) are .mu.-law code output level values at times t, and a.sub.i are weighting factors chosen to shape the frequency spectrum of out(t). The shaping filter may be used with multidimensional PAM constellations.

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"A Mathematical Theory of Communication". Bell Systems Technical Journal, 27:379-423, 623-656.

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