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Equalizer Network for Shielded Distributed Data Interface Transceiver

IP.com Disclosure Number: IPCOM000110977D
Original Publication Date: 1994-Jan-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Celenza, N: AUTHOR

Abstract

Disclosed is the circuit topology and specific component values for the Equalizer Network used in the IBM Shielded Distributed Data Interface (SDDI) Transceiver. This network enables the IBM SDDI Transceiver to transmit/receive 100 Mbt data over Shielded Twisted Pair (STP) cable with excellent system jitter response.

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Equalizer Network for Shielded Distributed Data Interface Transceiver

      Disclosed is the circuit topology and specific component values
for the Equalizer Network used in the IBM Shielded Distributed Data
Interface (SDDI) Transceiver.  This network enables the IBM SDDI
Transceiver to transmit/receive 100 Mbt data over Shielded Twisted
Pair (STP) cable with excellent system jitter response.

      SDDI data has frequency components from 50 Khz to 62 Mhz.  STP
cable causes data jitter due to increased signal attenuation for high
frequencies.  Amplifier circuits, needed to compensate for cable
signal attenuation, contribute more jitter due to their limited
frequency response.  The equalizer design in this disclosure
compensates for STP cable attenuation, amplifier high frequency
response, and data frequency components, such that we are able to
drive 100 meters of STP Type 1 cable and still have jitter low enough
for a reliable SDDI system.

      The equalizer is symmetrical in circuit topology and in
physical layout for best common-mode rejection.  It is optimized for
pulses of equal peak-to-peak amplitude from an 8 ns to a 48 ns wide
pulse by proper selection of component values, such that the
equalizer network has a zero at 15.6 Mhz, a zero at 42.6 Mhz, and two
complex poles at 52.0 Mhz.  The two zeros and two poles serve to peak
the signal response of the equalizer by 15 dB at 62 Mhz and the
overall system response by 8.75 dB at 62 Mhz.