METHOD FOR RECEIVING A SIGNAL, WHICH IS TRANSMITTED OVER A PAIR OF WIRES AND RECEIVER

Abstract

A method for receiving a signal, which is transmitted over a pair of wires is measuring a differential mode (DM) signal and is measuring a common mode (DM) signal and using both DM and CM to restore the original signal. A corresponding receiver (1) comprises a CM receiving path (3), a DM receiving path (2) and a digital signal processor (22) to combine CM and DM signals. With this method and receiver (1) the coverage of networks, which are slightly unbalanced, can be enhanced, especially in cases where the CM signal is less attenuated than the DM signal.

Description

The present invention and its numerous embodiments will be better understood on basis of the following exemplary description thereof taken in conjunction with the accompanying drawing, in which

FIG. 1 shows a circuit of a receiver according to a first embodiment of the present invention, and

FIG. 2 shows a circuit of a receiver according to a second embodiment of the present invention.

In FIG. 1 a schematic circuit for a receiver 1 is depicted, that is used in a PLC system. However receivers for xDSL-systems or other two-wire, mainly balanced, networks are working on the same basis. In a powerline grid (with Phase P, Neutral N and Ground PE), the signals are normally coupled into the grid as differential mode (DM) via a PLC modem, which acts as a transmitter (not shown). Due to inherent imbalances (light switches, current bars the fuse cabinet, branches, etc.) a part of the original pure DM signal is coupled into the common mode (CM) of the signal. Since the CM signal is more likely to radiate from the wires and cause interference, it has been disregarded so far to inject CM signals, but using the CM signal for receiving only, does not cause radiation.

However, the CM signal can be used to enhance the coverage of the networks (e.g. PLC systems or xDSL-systems). A receiver 1 to receive both the common mode and the differential mode is built of a differential mode receiving path 2 and a common mode receiving path 3.

The common mode receiving path 3 is built of a common mode choke 4 for highly attenuating the DM signals, but not affecting the CM signals and of a CM impedance matching network 5 for hindering reflections of the CM signal to be inputted into the network again.

The differential mode receiving path 2 is built of a differential mode choke 11, for highly attenuating common mode signals and not affecting DM signals, and a balun 12, which block CM signals, whereby DM signals are not affected and a DM impedance matching network 13, which are all connected in series. An additional common mode choke 14 is connected between the balloon 12 and a ground plane 15 in order to build a drain for the common mode signal.

Both the common mode receiving path 3 and the differential mode receiving path 2 are connected in parallel to the powerline gridlines P and N.

In the first embodiment of FIG. 1 both the common mode receiving path 3 and the differential mode receiving path 2 are coupled into one filter 20 and the filtered signal is converted to a digital signal in an analog-digital-converter (ADC, 21). The digitally converted signal is used by a digital signal processing unit (DSP, 23) to restore the original signal.

In the second embodiment of FIG. 2 the CM receiving path 3 and the DM receiving path 2 are coupled to separate filters, namely a CM filter 30 and a DM filter 31, which respective output signals are coupled to separate analog-digital-converters, namely a CM analog-digital-converter 32 and a DM analog-digital-converter 33, thereby giving the possibility to better adapt the CM filter 30 and the DM filter 31 to the CM signal and DM signal, respectively.

Even if the invention is described above with respect to a PLC-system, it is evident that it may be used for every network that is intended to be balanced, but certain inbalances occur, e.g. in xDSL-systems.

If PLC modems are integrated into big devices like a flat display of a personal computer (PC) a counterpoise for CM reception could easily be integrated.

Claims

1. Method for receiving a signal, which is transmitted over a pair of wires (P,N), comprising the steps of: measuring a differential mode of the signal,measuring a common mode of the signal,

2. Method according to claim 1, further comprising the steps of separating the differential and the common mode of the signal before measuring the modes.

3. Method according to claim 1 or 2, further comprising the steps of combining pure differential mode and pure common mode into one analog-digital-converter (21) and evaluating the modes in one digital signal processor (22).

4. Method according to claim 1 or 2, further comprising the steps of coupling the differential mode and the common mode into distinct analog-digital-converters (32,33).

5. Receiver (1) for wire-based communication signals comprising: a differential mode receiving path (2), a common mode receiving path (3) and a digital signal processor (22), which is connected to both receiving paths (2,3).

6. Receiver (1) according to claim 5 further comprising: a differential mode choke (11) in the differential mode receiving path (2).

7. Receiver (1) according to claim 5 or 6, further comprising: a common mode choke (4) in the common mode receiving path (3).

8. Receiver (1) according to claims 5 to 7, further comprising a differential mode impedance matching network (13) after the differential mode choke (11) in the differential mode receiving path (2).

9. Receiver (1) according to claims 5 to 8, further comprising a common mode impedance matching network (5) after the common mode choke (4) in the common mode receiving path (3).

10. Receiver (1) according to claim 5 to 9, further comprising one filter (20) to which input both the common mode receiving path (3) and the differential mode receiving path (2) are coupled.

11. Receiver (1) according to claims 5 to 9, further comprising a CM filter (30) and a DM filter (31) for the common mode receiving path (3) and the differential mode receiving path (2), respectively.

12. Receiver (1) according to claim 10, further comprising an analog digital converter (21) and a digital signal processor (22), which are connected in series to said one filter (20).

13. Receiver (1) according to claim 11, further comprising a CM analog digital converter (32) after the CM filter (30) and a DM analog digital converter (33) after the DM filter (31).

14. Receiver (1) according to any one of the claims 7 to 13, further comprising a further differential mode choke (14) in the differential mode receiving path (2) after the common mode choke (11) for coupling the common mode signal to ground (15) and a balun (12) between the common mode choke (11) the respective filter (20,31) for the DM mode.

15. Receiver (1) according to any one of the claims 5 to 14, characterized in that the received signals are Powerline-signals.

16. Receiver (1) according to any one of the claim 5 to 14, characterized in that the received signals are xDSL-signals.