Wideband transceiver with emi suppression

Abstract

A data communications transceiver for transmitting signals to and from the communicating medium, with the transceiver including an input terminal, a short time constant differentiator connected to the input terminal to differentiate signals applied thereto, a Schmitt trigger supplied with the output of the short time constant differentiator for producing a corresponding square wave output signal, a first driver supplied with the square wave output of the Schmitt trigger for supplying it to the communicating means, amplifying means for receiving signals from the communicating medium and for producing an amplified output therefrom, a second short time constant differentiator supplied with the output of the amplifying means and for supplying it to a second Schmitt trigger for producing a corresponding second square wave signal, and a second driver supplied with a second square wave signal for supplying it to an output terminal. In the preferred embodiment of the invention, electromagnetic interference is suppressed by connecting a bifilar transformer between the output of the first driver in the communicating medium, with the primary of the transformer being in series between the driver and the center conductor of the shielded communicating medium and with the secondary of the transformer being connected in series between the shield or the communicating medium and the floating ground of the transceiver circuit. A bypass capacitor is connected between the shield of the communicating medium and the circuit ground. Furthermore, an enable circuit is connected between the amplifying means and the second Schmitt trigger to only enable the Schmitt trigger when the amplitude of the received signal exceeds a predetermined minimum which is higher than threshold level of the Schmitt trigger.