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# Adaptive Amplitude and Interference Equalization

IP.com Disclosure Number: IPCOM000060482D
Original Publication Date: 1986-Apr-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 47K

IBM

## Related People

Schneider, RC: AUTHOR [+2]

## Abstract

An adaptive equalization loop is described where the read signal has symmetry, is less than 4-bit periods wide, and has unknown isolated pulse amplitude. As shown in Fig. 1, the unknown amplitude is designated A and the interference is I. The signal amplitude at time N is: SN = I DN-1 + A DN +I DN+1 (1) Although this is a single equation with two unknowns (I and A), a good approximation to I and A (I and A) can be derived by using the average values I- and A- . Hence, from (1): (Image Omitted) where DN = the detected signal at time N (-1,0,1). Note: Multiplication and division by Di is simple because Di e (-1,0,1). These equations can be implemented as the embodiment of Fig. 2.

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An adaptive equalization loop is described where the read signal has symmetry, is less than 4-bit periods wide, and has unknown isolated pulse amplitude. As shown in Fig. 1, the unknown amplitude is designated A and the interference is I. The signal amplitude at time N is: SN = I DN-1 + A DN +I DN+1 (1) Although this is a single equation with two unknowns (I and A), a good approximation to I and A (I and A) can be derived by using the average values I- and A- . Hence, from (1):

(Image Omitted)

where DN = the detected signal at time N (-1,0,1). Note: Multiplication and division by Di is simple because Di e (-1,0,1). These equations can be implemented as the embodiment of Fig. 2. A is then used to drive a variable gain amplifier (AGC) and I- is used to vary the amount of compensation (either delay line taps, or 1-F S2). An illustration of this circuit is shown in block form in Fig. 3. An adaptive loop is thus defined, that simultaneously obtains a measure of both amplitude and interference. Correction is done via AGC and variable compensation. When previous systems performed AGC, the effect of interference on signal amplitude was not considered.

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