Digital equalizer with overlappable filter taps

Abstract

In one illustrative embodiment, an equalizer includes: a shift register, an array of multipliers, an array of multiplexers, and a summer. The shift register provides receive signal samples at each tap. Each multiplier in the array multiplies one of said receive signal samples by a respective coefficient to produce a product, with at least one of said multipliers coupled to a fixed tap. Each multiplexer in the array supplies an associated one of said multipliers with a receive signal sample from a selectable tap. The summer sums the products to produce a filtered output signal. To reduce hardware requirements, coefficient multipliers may be multiplexed to a reduced set of taps, and the dynamic range of the coefficients may be increased by overlapping the sets for different multipliers. Methods of tap selection and coefficient adaptation are disclosed.

Description

Background technique [0001] Digital communications occur between a sending device and a receiving device through an intermediate communications medium or "channel" (eg, fiber optic cable or insulated copper wire). Each transmitting device typically transmits symbols at a fixed symbol rate, while each receiving device detects the (possibly corrupted) symbol sequence and attempts to reconstruct the transmitted data. A "symbol" is a state or validity condition of a channel that lasts for a fixed period of time, called a "symbol interval". A symbol may be, for example, a voltage or current level, an optical power level, a phase value, or a specific frequency or wavelength. A change from one channel state to another is called a symbol transition. Each symbol may represent (ie, encode) one or more binary bits of data. Alternatively, data may be represented by symbol transitions or by a sequence of two or more symbols. [0002] Many digital communication links use only one bit pe...

AI Technical Summary

Problems solved by technology

[0002] Many digital communication links use only one bit per symbol; a binary "0" is represented by one symbol (e.g., a voltage or current signal in a first range), and a binary "1" is represented by another symbol (e.g., , a voltage or current signal in the second range), but higher order signal constellations are known and frequently used

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