Circuit to eliminate signal chatter in the output of a fiber-optic receiver

• US 5,391,950 A
• Filed: 06/24/1993
• Issued: 02/21/1995
• Est. Priority Date: 06/24/1993
• Status: Expired due to Term

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Unisys Corporation
• Inventors: Krawczak, John A.
• Primary Examiner(s): Heyman, John S.
• Assistant Examiner(s): TON, MY TRANG
• Application Number:
  US08/080,545
• Time in Patent Office: 607 Days
• Field of Search: 307/542.1, 307/360, 307/361, 307/350, 307/351, 307/490, 307/494, 307/491, 307/359
• US Class Current: 327/384
• CPC Class Codes: H03K 5/082 with an adaptive threshold
• CPC Class Codes: H04L 25/062 Setting decision thresholds using feedforward techniques only

Abstract

A signal processing circuit that is subject to signal chatter is provided with signal chatter-elimination circuitry. Prior signal processing circuitry included a peak voltage detector which received a data input signal and provided a peak voltage representation of the input signal and a threshold-comparator that provided a threshold-comparison signal of a first output voltage magnitude when the peak voltage representation was below a predefined threshold voltage and of a second output voltage magnitude when the peak voltage representation was above the predefined threshold voltage. Improved signal chatter elimination is achieved by the further incorporation of a differential operational amplifier that has (a) a first input terminal that receives a data-representative signal which is subject to signal chatter, (b) a second input terminal that is coupled to receive a threshold-comparison signal of either a first fixed voltage level that blocks the output signal, or of a second variable voltage level that allows the output signal to be provided by the amplifier, and (c) a source of second variable voltage level which is temperature compensated, and the further incorporation of a threshold-level switch coupled to the threshold-comparator to receive the threshold comparison signal and to the amplifier, wherein the threshold-level switch is constructed to supply the first fixed voltage level to the second input terminal when the input signal is below the threshold voltage and the second voltage level to the second input terminal when the input signal is above the threshold voltage.

Claims

1. A signal chatter elimination circuit for the elimination of signal chatter in a data signal comprising:

a peak voltage detector that receives said data signals and is constructed to provide a peak voltage signal that is representative of the peak voltage of said data signal,

a threshold comparator that is coupled to said peak voltage detector for receiving said peak voltage signal that is constructed to provide a control signal that is at a first voltage level when said peak voltage signal has a magnitude that is below a defined threshold voltage magnitude and is at a second voltage level when said peak voltage is above said defined threshold voltage magnitude,

a differential amplifier which is capable of supplying an output signal representative of said data signal which comprises;

(a) a first input terminal coupled to receive said data signal which causes an output of said differential amplifier to be driven in a first polarity direction in response to said data signal,

(b) a second input terminal coupled to receive an applied signal that causes said output to be driven in a second polarity direction in response to said applied signal, and

(c) a variable voltage level source which provides a temperature compensation signal, and

a threshold-level switcher coupled to said threshold-comparator to receive a threshold comparison signal and to said differential amplifier, which is constructed to supply said control signal to said second input terminal,

wherein temperature compensation signal is also coupled to said second input terminal so that said applied signal comprises said control signal and said temperature compensation signal and said second voltage level is of a magnitude such that said output signal of said differential amplifier is supplied at a fixed voltage level when said control signal is at said second voltage level.

2. A signal chatter elimination circuit as claimed in claim 1 wherein said threshold-level switcher comprises first and second operational amplifier voltage followers coupled in cascade, wherein each voltage follower comprises a signal input terminal, a reference input terminal and an output terminal, and said signal input terminal of said first voltage follower is coupled to said threshold comparator to receive said control signal, said output terminal of said first voltage follower is coupled to said signal input terminal of said second voltage follower, said output terminal of said second voltage follower is coupled to said second input terminal of said differential amplifier, said reference input terminal of said first voltage follower is coupled to a reference voltage and said reference terminal of said second voltage follower is coupled to said source of said temperature compensation signal.