Serial signal injection using capacitive and transformer couplings for power line communications
View Patent ↗A coupling network has a first power line interface port and a power line modem interface configured to be coupled to a power line modem transceiver. An inductor-capacitor circuit coupled to the power line modem interface has a low-impedance resonant frequency at a signal frequency of the power line modem transceiver. An inductor having a corner frequency between the signal frequency and the power line frequency has a first end and a second end. The first end of the inductor is connected to the inductor-capacitor circuit and a second end of the inductor is coupled to an alternating current ground coupled to the transceiver ground. The inductor couples the first power line interface port to a power supply interface port.
1. A coupling network comprising:
a first power line interface port for connecting said network to a power line that carries a power signal characterized by a power line frequency;
a power line modem interface configured to be coupled to a power line modem transceiver that receives a signal characterized by a signal frequency;
an inductor-capacitor circuit coupled to the power line modem interface and having a low-impedance resonant frequency of the power line modem transceiver;
an alternating current ground coupled to a transceiver ground;
an inductor having a corner frequency between the signal frequency and the power line frequency, and having a first end and a second end, the first end of the inductor being connected to the inductor-capacitor circuit and the second end of the inductor being coupled to the alternating current ground; and
a power supply interface port coupled to the first power line interface port through the inductor.
2. The coupling network of claim 1 wherein the inductor is a winding of a transformer.
3. The coupling network of claim 1 wherein the first end of the inductor is connected to the first power line interface port.
4. The coupling network of claim 1 wherein the first end of the inductor is connected to the power supply interface port.
5. The coupling network of claim 1 further comprising a capacitor coupled to the first power line interface port and to a second power line interface port.
6. The coupling network of claim 5 wherein the capacitor has an impedance less than about 20 ohms at a signal frequency of the coupling network.
7. The coupling network of claim 5 wherein the capacitor has an impedance less than about 12 ohms at a signal frequency of the coupling network.
8. The coupling network of claim 5 wherein the capacitor has an impedance not greater than about 6 ohms at a signal frequency of the coupling network.
9. The coupling network of claim 5 further comprising a first power line lead connected to the second power line interface port.
10. The coupling network of claim 9 further comprising a second power line lead connected to the power supply interface port; and
a power supply connected to the first power line lead and to the second power line lead.
11. The coupling network of claim 9 wherein the power supply is a linear power supply.
12. The coupling network of claim 9 wherein the power supply is a switching power supply.
13. The coupling network of claim 12 wherein a transformer operates in conjunction with the capacitor to form an EMI filter.
14. The coupling network of claim 1 further comprising the power line modem transceiver.