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# Time Domain Adjustable Equalizer

IP.com Disclosure Number: IPCOM000089220D
Original Publication Date: 1977-Oct-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 39K

IBM

## Related People

Castro, F: AUTHOR [+2]

## Abstract

The adjustable equalizer shown above allows for separate pulse slimming and distortion adjustments which do not interact. Also, a single potentiometer is used to effect bidirectional distortion adjustment.

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Time Domain Adjustable Equalizer

The adjustable equalizer shown above allows for separate pulse slimming and distortion adjustments which do not interact. Also, a single potentiometer is used to effect bidirectional distortion adjustment.

A basic equalizer stage for pulse slimming and distortion correction can be written in the Laplace domain as: Vo over Vi(S) = (1 + AS) (1 - BS) = 1 + (A - B)S - ABS)/2/.

This can be viewed as taking the original signal, adding (A - B) times the first derivative, and subtracting AB times the second derivative. This function can be implemented in various ways. However, the adjustment of A and B each control simultaneously the first derivative amplitude and the second derivative amplitude, making adjustments in the time domain very difficult.

The circuit shown in Fig. 1 overcomes this difficulty and makes the adjustment procedure simple because there is no interaction between second derivative gain, which controls pulse slimming, and first derivative gain, which controls distortion. Also, making the sign of the first derivative either positive or negative with a single potentiometer (pot) makes it possible to correct distortion without knowing beforehand its direction. From the diagram in Fig. 1, Vo = Vi + dVi over dt(+/- K2) - d/2/ over dt/2/ (Vi) K1 or Vo over Vi(S) = 1 + (+/- K2)S - K1S/2/

Adjustment of the pot shown in Fig. 2 gives more distortion correction in one direction than it does in the other direction. When the pot is...