Browse Prior Art Database

Adaptive Equalization Circuit

IP.com Disclosure Number: IPCOM000052026D
Original Publication Date: 1981-Apr-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Hong, JH: AUTHOR

Abstract

The article discloses a differential amplifier circuit in which opposed transistors operate in switching, linear or mixed linear/switching modes to adaptively compensate for skin effect losses in cables

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 67% of the total text.

Page 1 of 2

Adaptive Equalization Circuit

The article discloses a differential amplifier circuit in which opposed transistors operate in switching, linear or mixed linear/switching modes to adaptively compensate for skin effect losses in cables

In data transmission systems using coaxial or twisted pair cables, the transmitted signal is attenuated due to the skin effect loss in the cable. The loss is a direct function of frequency. For broadband signals, communication becomes difficult without equalization, i.e., compensation for this frequency- dependent attenuation.

This article relates to a particularly simple dynamic equalizer for use in serial high-speed data communication systems.

The circuit diagram of the new equalizer is shown in Fig. 1. It is basically a differential amplifier and, as such, has two basic operating modes: linear and switching. When the input signal, Vin, is small, transistors Q1 and Q2 operate in the linear mode, and the simplified small signal equivalent circuit as shown in Fig. 2 is valid. The small signal transfer function is approximately equal to the following. G(jOmega) = (Rc gm) over 2 (1 over 1 gm R1) (jOmega a) over JOmega b) where a = 1 over Ce R2 and b = 1 over Ce R2 (1 R2 over R1).

Fig. 3 shows the magnitude plot of G(jOmega). By choosing R1, R2 and Ce appropriately, the equalizer can be designed to compensate for skin effect for any specified maximum cable length.

When the same equalizer is used with a cable of less-than-maximum length, ...