Magnetic circuit for high speed automotive ethernet over UTP channels
View Patent ↗The present disclosure is directed to apparatuses for preventing significant amounts of common mode noise from a PHY transceiver, such as an Ethernet PHY transceiver, from coupling to an unshielded twisted-pair cable. The apparatuses can provide common mode noise isolation, while limiting any common mode noise to differential mode noise (CM-DM) conversion. Common mode noise is generally ignored by a PHY transceiver that receives a differential data signal because of differential signaling. However, when common mode noise is converted to differential mode noise, then data errors can result. Thus, limiting any CM-DM conversion is important.
1. A transceiver, comprising:
a physical layer device (PHY) configured to send and receive differential data signals via a media dependent interface (MDI) over an unshielded twisted pair (UTP) cable;
a common mode choke (CMC), coupled between an input/output port of the PHY and the MDI, and configured to provide a low impedance to the differential data signals and a high impedance to common mode noise;
a common mode termination (CMT) configured to provide a matched termination for the common mode noise; and
a differential mode choke (DMC), coupled between the UTP cable and the CMT, configured to provide a low impedance for the common mode noise and a high impedance for the differential data signals,
wherein the CMT includes an input node connected to an output of the DMC and includes another node connected to ground.
2. The transceiver of claim 1 , wherein the DMC comprises a core, a first winding, and a second winding, wherein the first winding and the second winding are wound in opposite directions around the core so that the first and second windings are inversely coupled.
3. The transceiver of claim 2 , further comprising:
a voltage supply connected to a first end of the first winding, wherein a second end of the first winding is connected to a first wire of the UTP cable.
4. The transceiver of claim 3 , wherein a first end of the second winding is connected to ground through the CMT, and wherein a second end of the second winding is connected to a second wire of the UTP cable.
5. The transceiver of claim 4 , further comprising:
a capacitor connected between the first end of the first winding and the first end of the second winding to provide a common mode reference at an input of the CMT.
6. The transceiver of claim 1 , further comprising:
a direct current (DC) blocking capacitor coupled between an output port of the CMC and the UTP cable.
7. The transceiver of claim 1 , wherein the differential data signals are Ethernet differential data signals.
8. The transceiver of claim 1 , wherein the transceiver is implemented in an automobile.
9. A transceiver, comprising:
a physical layer device (PHY) configured to send and receive differential data signals via a media dependent interface (MDI) over an unshielded twisted pair (UTP) cable;
a first common mode choke (CMC), coupled between an input/output port of the PHY and the MDI, and configured to provide a low impedance to the differential data signals and a high impedance to common mode noise;
a common mode termination (CMT) configured to provide a matched termination for the common mode noise; and
a second CMC, coupled between the UTP cable and the CMT, configured to provide a low impedance for the common mode noise and a high impedance for the differential data signals,
wherein the CMT includes an input node connected to an output of the second CMC and includes another node connected to ground.
10. The transceiver of claim 9 , wherein the second CMC comprises a core, a first winding, and a second winding, wherein the first winding and the second winding are wound in the same direction around the core.
11. The transceiver of claim 10 , further comprising:
a voltage supply connected to a first end of the first winding, wherein a second end of the first winding is connected to a first wire of the UTP cable.
12. The transceiver of claim 11 , wherein a first end of the second winding is connected to ground through the CMT, and wherein a second end of the second winding is connected to a second wire of the UTP cable.
13. The transceiver of claim 12 , further comprising:
a capacitor connected between the first end of the first winding and the first end of the second winding to provide a common mode reference at an input of the CMT.
14. The transceiver of claim 9 , further comprising:
a direct current (DC) blocking capacitor coupled between an output port of the first CMC and the UTP cable.
15. The transceiver of claim 9 , wherein the differential data signals are Ethernet differential data signals.
16. The transceiver of claim 9 , wherein the transceiver is implemented in an automobile.
17. A transceiver, comprising:
a physical layer device (PHY) configured to send and receive differential data signals via a media dependent interface (MDI) over an unshielded twisted pair (UTP) cable;
a common mode choke (CMC), coupled between an input/output port of the PHY and the MDI, and configured to provide a low impedance to the differential data signals and a high impedance to common mode noise;
a common mode termination (CMT) configured to provide a matched termination for the common mode noise; and
an autotransformer, coupled between the UTP cable and the CMT, configured to provide a low impedance to the common mode noise and a high impedance for the differential data signals,
wherein the CMT includes an input node connected to a center tap of the autotransformer and includes another node connected to ground.
18. The transceiver of claim 17 , further comprising:
a direct current (DC) blocking capacitor coupled between an output port of the CMC and the UTP cable.
19. The transceiver of claim 17 , wherein the differential data signals are Ethernet differential data signals.
20. The transceiver of claim 17 , wherein the transceiver is implemented in an automobile.
21. The transceiver of claim 17 , wherein the autotransformer includes a single winding having the center tap, wherein a first end of the single winding is connected to a first wire of the UTP cable, and a second end of the single winding is connected to a second wire of the UTP cable.