LAN electro-optical interface

• US 5,251,054 A
• Filed: 10/24/1991
• Issued: 10/05/1993
• Est. Priority Date: 10/24/1991
• Status: Expired due to Fees

• Current Assignee: General Motors Corporation (General Motors Company)
• Original Assignee: General Motors Corporation (General Motors Company)
• Inventors: Lynn, Mark A.
• Primary Examiner(s): Chilcot, Jr., Richard E.
• Assistant Examiner(s): NEGASH, KINFE MICHAEL
• Application Number:
  US07/782,177
• Time in Patent Office: 712 Days
• Field of Search: 359/189, 359/154, 359/118, 359/158, 250/214 A, 250/214 B, 330/59, 330/308, 307/475
• US Class Current: 398/202
• CPC Class Codes: H03F 3/08 controlled by light
• CPC Class Codes: H04B 10/6972 using passive filtering

Abstract

A receiver circuit for a LAN electro-optical interface includes a high pass filter connected between the optical signal receiving element and the standard ECL line receiver. The high pass filter removes noise from the signal output by the optical signal receiving element, thereby reducing the bit error rate of the system and/or increasing the effective sensitivity of the system, enabling the signal transmission distance to be increased.

Claims

1. An apparatus coupled between an analog receiver and a line receiver means, comprising:

first filter means for receiving an electrical signal from the analog receiver and for first filtering the electrical signal, filtering low frequency noise from the electrical signal while passing data signals contained in the electrical signal, the data signals having a data frequency, the first filter means outputting a first filtered signal at a first filter output;

amplification means, connected to the output of the first filter means, for amplifying the first filtered signal, outputting, as a result, an amplified signal;

second filter means, coupled between the amplification means and the line receiver means, for receiving the amplified signal and for second filtering the amplified signal to filter high frequency noise from the amplified signal while passing data signals contained in the amplified signal, the second filter means outputting a second filtered signal to the line receiver means, which, in response thereto, outputs a robust square signal, whereby the sensitivity of the system is increased,

wherein the first filter means comprises

a parallel circuit including a first resistor connected in parallel with a capacitor, the parallel circuit having a first connection and a second connection, the first connection coupled to the output of the analog receiver and the second connection coupled to the amplification means; and

a second resistor connected between the second connection of the parallel circuit and ground,

whereby the first filter means comprises a first order high pass filter having a break frequency below the data frequency and operational to attenuate low frequency noise, which comprises all frequencies below the break frequency, whereby the first filter means decreases a bit error rate of the apparatus and increases sensitivity of the system.

2. An apparatus coupled between an analog receiver and a line receiver means, comprising:

first filter means for receiving an electrical signal from the analog receiver and for first filtering the electrical signal, filtering low frequency noise from the electrical signal while passing data signals contained in the electrical signal, the data signals having a data frequency, the first filter means outputting the first filtered signal at a first filter output;

amplification means, connected to the output of the first filter means, for amplifying the first filtered signal, outputting, as a result, an amplified signal;

second filter means, coupled between the amplification means and the line receiver means, for receiving the amplified signal and for second filtering the amplified signal, filtering high frequency noise from the amplified signal while passing data signals contained in the amplified signal, the second filter means outputting the second filtered signal to the line receiver means, which, in response thereto, outputs a robust square signal, whereby the sensitivity of the system is increased

wherein the amplification means comprises

a high gain transistor amplifier, coupled between the first filter means and the second filter means, including a transistor and biasing resistors, whereby the amplification means increases system sensitivity.

3. An apparatus coupled between an analog receiver and a line receiver means, comprising:

first filter means for receiving an electrical signal from the analog receiver and for first filtering the electrical signal, filtering low frequency noise from the electrical signal while passing data signals contained in the electrical signal, the data signals having a data frequency, the first filter means outputting the first filtered signal at a first filter output;

amplification means, connected to the output of the first filter means, for amplifying the first filtered signal, outputting, as a result, an amplified signal;

second filter means, coupled between the amplification means and the line receiver means, for receiving the amplified signal and for second filtering the amplified signal, filtering high frequency noise from the amplified signal while passing data signals contained in the amplified signal, the second filter means outputting the second filtered signal to the line receiver means, which, in response thereto, outputs a robust square signal, whereby the sensitivity of the system is increased

wherein the second filter means comprises

a series circuit including a resistor and a capacitor connected in series, the series circuit coupled between a voltage source and ground, an output of the amplification means connected to the connection between the resistor and capacitor, wherein the series circuit comprises a low pass filter having a break frequency above the data frequency and operational to attenuate high frequency noise characterized as all frequencies above the break frequency and whereby the second filter means decreases a bit error rate of the apparatus and increases sensitivity of the system.

4. An apparatus coupled between an analog receiver and a line receiver means, comprising:

a parallel circuit including a first resistor connected in parallel with a first capacitor, the parallel circuit having a first parallel circuit connection and a second parallel circuit connection, the first connection coupled to an output of the analog receiver;

a second resistor connected between the second connection of the parallel circuit and ground;

a high gain transistor amplifier, coupled to the second connection of the parallel circuit, including a transistor and third and fourth resistors for biasing a base of the transistor;

a series circuit including a fifth resistor and a second capacitor connected in series, the series circuit coupled between a voltage source and ground, the connection between fifth resistor and the second capacitor coupled to a collector of the transistor,

whereby the parallel circuit, second resistor, and series circuit act as a band pass filter having a first break frequency below a data frequency and a second break frequency above the data frequency and operational to attenuate low frequency noise and high frequency noise, wherein low frequency noise comprises all frequencies below the first break frequency and high frequency noise comprises all frequencies above the second break frequency, and whereby the band pass filter decreases a bit error rate of the apparatus and increases sensitivity of the system, and

whereby the high gain amplifier increases system sensitivity.