System for crosstalk noise reduction on twisted pair, ethernet, polyphase and shielded wire systems
The present invention is an electronic circuit that reduces crosstalk in communications systems employing twisted pair, Ethernet, polyphase or shielded wire transmission media. The present invention includes three stages of crosstalk noise reduction. Stage 1 filters common mode noise from the transmission media and balances the resistive and reactive parasitic electrical characteristics of the transmission media that couple each line to the local ground over the operating frequency band. The second Stage performs differential crosstalk noise reduction in real time using multiple feedback loops. It can dynamically locate and set optimal system operating conditions for minimal differential crosstalk coupling for the specific environmental and interfering channel utilization conditions. The third Stage utilizes digital signal processing techniques to further reduce any residual crosstalk after analog-to-digital conversion. The third Stage also functions as a digital controller for the entire system as well as portions of subsystems including the feedback loops of Stage 2.
1 . An crosstalk noise reduction system comprising:
a first stage, comprising passive crosstalk noise reduction circuits operating on signals from a transmission media;
a second stage, comprising active crosstalk noise reduction circuits and multiple feedback loops; and
a third stage, comprising a digital signal processor.
2 . The crosstalk noise reduction system of claim 1 wherein said first stage is configured to filter common mode noise from a transmission media and balance the resistive and reactive parasitic electrical characteristics of said transmission media that couple each line.
3 . The crosstalk noise reduction system of claim 1 wherein said second stage is configured to perform differential crosstalk noise reduction in real time.
4 . The crosstalk noise reduction system of claim 1 wherein said third stage is configured to reduce residual crosstalk after analog-to-digital conversion.
5 . The crosstalk noise reduction system of claim 1 wherein said third stage digitally controls said crosstalk noise reduction system and portions of subsystems of said second stage.
6 . The crosstalk noise reduction system of claim 5 wherein said third stage uses two inputs from said first and second stage to adjust control signals sent to calibrate components in said second stage.
7 . The crosstalk noise reduction system of claim 6 wherein the first of said two inputs is from an A/D converter converting a receiving signal from in transmission media and the second of said two inputs is from an A/D converter converting a common mode signal in said transmission media.
8 . The crosstalk noise reduction system of claim 1 wherein said second stage further comprises:
a common mode sense;
an A/D converter;
a first amplifier receiving output signal from said common mode sense;
a second amplifier receiving output signal from said common mode sense; and
a synchronous AM detector.
9 . The crosstalk noise reduction system of claim 8 wherein said second stage further comprises:
a summing node configured to use output from said second amplifier to cancel crosstalk noise in a receiving signal from said transmission media.
10 . The crosstalk noise reduction system of claim 9 wherein said second stage further comprises:
an AGC control configured to receive control signals from said third stage to control said second amplifier.