Device for discriminating between two values of a signal with DC offset compensation

• US 4,363,977 A
• Filed: 02/20/1981
• Issued: 12/14/1982
• Est. Priority Date: 02/20/1980
• Status: Expired due to Term

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Yamaguchi, Kazuo, Murakami, Norio, Chujo, Takafumi, Murano, Kazuo, Tsuda, Toshitaka, Takahashi, Motohide
• Primary Examiner(s): Zazworsky, John
• Application Number:
  US06/236,609
• Time in Patent Office: 662 Days
• Field of Search: 307/264, 307/359, 307/351, 307/546, 307/555, 307/562, 307/311, 328/162, 328/165, 328/168, 328/175, 358/34, 358/36, 358/71, 340/146.3 AC, 340/146.3 AE, 340/146.3 AG, 330/9, 330/11
• US Class Current: 327/73
• CPC Class Codes: G01R 19/0038 Circuits for comparing several input signals and for indicating the result of this comparison, e.g. equal, different, greater, smaller (comparing pulses or pulse trains according to amplitude)
• CPC Class Codes: H03K 5/2427 using clock signals
• CPC Class Codes: H04B 10/6911 Photodiode bias control, e.g. for compensating temperature variations
• CPC Class Codes: H04B 10/695 Arrangements for optimizing the decision element in the receiver, e.g. by using automatic threshold control
• CPC Class Codes: H04L 25/062 Setting decision thresholds using feedforward techniques only
• CPC Class Codes: H04L 25/065 Binary decisions

Abstract

A device for discriminating between two values of a signal using DC offset compensation including an automatic gain control circuit, a peak detector circuit and a feedback path from the peak detector circuit to the input circuit of the automatic gain control circuit. The value of the feedback current is regulated so that the maximum value of one of the same polarity signals and the opposite polarity signal coincides with the minimum value of the other of the two signals.

Claims

1. A device for discriminating between two values of a signal using DC offset compensation, comprising:

an automatic gain control circuit, having an input, for receiving an incoming signal and for generating both a same polarity signal having the same polarity as said incoming signal and an opposite polarity signal having opposite polarity to that of said incoming signal;

a peak detector device, operatively connected to said automatic gain control circuit, for receiving said same polarity signal and said opposite polarity signal and for generating and controlling the value of a feedback current;

a feedback path for connecting the output of said peak detector device with the input of said automatic gain control circuit;

a level shift circuit, operatively connected to said automatic gain control circuit, for generating a shifted same polarity signal by shifting the level of said same polarity signal; and

a comparator, operatively connected to said level shift circuit and said automatic gain control circuit, for receiving said shifted same polarity signal and said opposite polarity signal through said level shift circuit and for generating a two value discriminated output signal in dependence upon said shifted same polarity signal and said opposite polarity signal, wherein the value of said feedback current is regulated so that the maximum value of one of said same polarity signal and said opposite polarity signal coincides with the minimum value of the other of said two polarity signals.

2. A device for discriminating between two values of a signal using DC offset compensation and automatic gain control, comprising:

an automatic gain control circuit, having an input and a feedback terminal, for receiving an incoming signal and for generating both a same polarity signal having the same polarity as said incoming signal and an opposite polarity signal having opposite polarity to that of said incoming signal;

a first level shift circuit, operatively connected to said automatic gain control circuit, for generating a shifted same polarity signal by shifting said same polarity signal and for passing therethrough said opposite polarity signal;

a first peak detection circuit, operatively connected to said first level shift circuit, for receiving the output of said first level shift circuit and for peak-detecting the difference between said shifted same polarity signal and said opposite polarity signal;

a second level shift circuit, operatively connected to said automatic gain control circuit, for generating a shifted opposite polarity signal by shifting said opposite polarity signal and for passing therethrough said same polarity signal;

a second peak detection circuit, operatively connected to said second level shift circuit, for receiving the output of said second level shift circuit and for peak-detecting the difference between said shifted opposite polarity signal and said same polarity signal;

a first feedback path for connecting the output of said first peak detection circuit with the input of said automatic gain control circuit to effect DC feedback;

a second feedback path for connecting the output of said second peak detection circuit with the feedback terminal of said automatic gain control circuit to effect automatic gain control; and

a comparator, operatively connected to said automatic gain control circuit, for receiving said same polarity signal and said opposite polarity signal, for generating a two value discriminated output signal, wherein said DC feedback by said first feedback path is carried out so that the minimum value of said opposite polarity signal coincides with the maximum value of said shifted same polarity signal.

3. A device as defined in claim 2, wherein said automatic gain control by said second feedback path is carried out so that the minimum value of said same polarity signal coincides with the maximum value of said shifted opposite polarity signal.

4. A device for discriminating between two values of an incoming signal, comprising:

an automatic gain control circuit, operatively connectable to receive the incoming signal, for generating a first signal and a second signal;

a level shift circuit, operatively connected to said automatic gain control circuit, for shifting the first signal by a predetermined value;

a peak detector, operatively connected to said automatic gain control circuit, for detecting the peak of a difference between the first and the second signal and for generating a feedback signal in dependence on said difference, said automatic gain control circuit generating the first and second signals in dependence upon the feedback signal and the incoming signal; and

a comparator, operatively connected to said automatic gain control circuit and to said level shift circuit, for comparing the second signal with the shifted first signal and for generating a discriminated signal in dependence upon the comparison, so that the two values of the incoming signal are discriminated.

5. A device for discriminating between two values of an incoming signal, comprising:

an automatic gain control circuit, operatively connectable to receive the incoming signal, for generating a first signal and a second signal;

a first level shift circuit, operatively connected to said automatic gain control circuit, for shifting the first signal by a first predetermined value and for passing therethrough the second signal;

a first peak detector circuit, operatively connected to said first level shift circuit and to said automatic gain control circuit, for detecting the peak of a first difference between the shifted first signal and the second signal and for generating a feedback signal in dependence on the first difference;

a second level shift circuit, operatively connected to said automatic gain control circuit, for shifting the second signal by a second predetermined value and for passing therethrough the first signal;

a second peak detector, operatively connected to said second level shift circuit and to said automatic gain control circuit, for detecting the peak of a second difference between the shifted second signal and the first signal and for generating the gain control signal in dependence on the second difference, said automatic gain control circuit generating the first and second signals in dependence upon the incoming signal, the feedback signal and the gain control signal; and

a comparator, operatively connected to said automatic gain control circuit, for comparing the second signal and the first signal and for generating a discriminated signal in dependence upon the comparison, so that the two values of the incoming signal are discriminated.