Bipolar signal processing circuit

• US 4,007,382 A
• Filed: 06/27/1975
• Issued: 02/08/1977
• Est. Priority Date: 02/12/1975
• Status: Expired due to Term

• Current Assignee: Canadian National Railway Company
• Original Assignee: Canadian National Railway Company
• Inventors: Warberg, John Martin
• Primary Examiner(s): Heyman, John S.
• Application Number:
  US05/590,828
• Time in Patent Office: 592 Days
• Field of Search: 307/235 A, 307/235 K, 307/235 N, 307/236, 328/146, 328/118, 328/147, 328/149
• US Class Current: 327/30
• CPC Class Codes: H04L 25/4925 using balanced bipolar ternary codes

Abstract

A bipolar signal is recovered and separated into its positive portion and its negative portion. The incoming bipolar signal and its inverted form are separately compared to a switched threshold. Switching of the threshold from a low standby level to a high level is effected by feedback of the output signals. The circuit generates a switched reference signal which is applied to two comparator circuits, one for the bipolar signal, the other for the inverted bipolar signal, and a hysterisis generator switches the threshold to its high level when a comparator circuit produces an output signal.

Claims

1. A bipolar signal processing circuit for recovering and processing a bipolar signal that could be degraded and for separately representing the positive and the negative portions of said bipolar signal, comprising:

input means for receiving a bipolar signal, an inverter circuit coupled to said input means for inverting the bipolar signal, a first comparator circuit having a reference input and having a signal input coupled to the output of said inverter circuit for producing a first output signal when the instantaneous value of the signal at its signal input exceeds the instantaneous value of the signal at its reference input, a second comparator circuit having a reference input and having a signal input coupled to said input means for producing a second output signal when the instantaneous value of the signal at its signal input exceeds the instantaneous value of the signal at its reference input, a peak voltage generator circuit connected to said input means for producing a reference voltage whose amplitude approaches the peak voltage of said bipolar signal, a grounded potential divider connected to the output of said peak voltage generator and having its junction connected to said reference inputs, an electronic switch connected across the grounded leg of said potential divider for substantially reducing the impedance of said potential divider whenever said switch is conductive, and an OR-gate circuit connected to said switch for maintaining said switch conductive during the presence of one of said first and second output signals, whereby said first output signal represents one of said positive and said negative portions of said bipolar signal and whereas said second output signal represents the other one of said portions of said bipolar signal.

2. The processing circuit as defined in claim 1 wherein the voltage applied to said reference inputs during the presence of said first or second output signals is approximately 75% of the peak voltage of said bipolar signal.

3. The processing circuit as defined in claim 2 wherein the voltage applied to said reference inputs during the absence of said output signals is approximately 25% of the peak voltage of said bipolar signal.

4. The processing circuit as defined in claim 1 wherein said electronic switch comprises the series connection of a resistor and the collector-emitter junction of a NPN transistor whose base is connected to the output of said OR-gate circuit.

5. The processing circuit defined in claim 4 wherein said peak voltage generator circuit comprises an operational amplifier whose first input is short-circuited to the amplifier'"'"'s output, and an R-C charging circuit connected between said input means through a rectifier and the other input of said operational amplifier.