WO2014037351A1 - Signal combining device and associated method - Google Patents

Abstract

There is provided a signal combining device (10) comprising a plurality of inputs (12, 14, 16), each input connectable to signal paths carrying signals of different frequency ranges such as RF, xDSL and power, and an output (20) connectable to a coaxial cable (52), wherein first and second inputs (12, 14) form inputs to a combination filter (30), and a third input (16) is connected to an output of the combination filter (30) to create a combined signal output path (18). The first input (12) is adapted to receive an xDSL signal with a signal conversion device (24) in the form of a balun disposed intermediate the first input and the combination filter (30) for converting an xDSL signal to an asymmetric signal. A method of combining multiple signals having different frequency bands is also provided.

Description

Title: Signal Combining Device and Associated Method Field of the invention

This invention relates to a signal combining device for combining signals having multiple frequencies and an associated method for combining such signals.

Background to the invention

For cable television and broadband networks, relaying all necessary data signals to a user can involve several cables to accommodate different signal frequencies used for different types of data. For example where RF signals are involved, coaxial cable is used and for xDSL signals, twisted pair cable is used. Generally a two-wire power cable is also required to power the network at the user end. Having several different cables can complicate installation and add to ingress problems as where a plurality of cables are involved, more connectors are needed so adding to the potential for ingress.

Summary of the invention

In accordance with one aspect of the present invention, there is provided a signal combining device comprising a plurality of inputs, each input connectable to signal paths carrying signals of different frequency ranges and an output connectable to a coaxial cable, wherein first and second inputs form inputs to a combination filter, such as a diplex filter, and a third input is connected to an output of the combination filter to create a combined signal output path, the first and second inputs form inputs to a combination filter, and a third input is connected to an output of the combination filter to create a combined signal output path, the first input adapted to receive an xDSL signal and a signal conversion device disposed intermediate the first input and the combination filter for converting an xDSL signal to an asymmetric signal. In this way, signals having different frequency ranges are combined into a single output path.

The xDSL signal prior to conversion is symmetric in that it has a positive and negative signal wire and is carried by a twisted pair cable, one wire a positive line and the other wire a negative line. This is the case even for the sub-category of xDSL signals called ADSL where the A stands for asymmetric but in this case "asymmetric" means that the ADSL signal has a different downstream speed to an upstream speed. The signal conversion device makes the signal asymmetric by converting it into a signal transmissible along a signal wire versus ground rather than a positive and negative signal wire as with the unconverted xDSL signal.

Preferably the xDSL signal is a VDSL-2 signal and the first input is adapted to receive VDSL-2 signals from an optical transceiver.

The signal conversion device may of preference be a balun or other type of transformer.

Desirably the second and third inputs are connectable to RF signals and power signals respectively, with the power signal of particular advantage where the signal receivable at the first input is a VDSL-2 signal as this will ensure power for the optical transceiver.

Where the combination filter is a diplex filter, preferably the first input is connected to a low pass side of the diplex filter and the second input is connected to a high pass side of the diplex filter.

The third input may be connected to with the output of the combination filter by disposing a power inserter device between the third input and the output of the combination filter.

Preferably the power inserter comprises capacitive and inductive elements to allow for impedance matching so as to improve return loss at lower frequencies, typically frequencies below lMHz.

Typically the signal combining device will be bi-directional, allowing received multiple signals with mutually exclusive frequency bands to be combined onto a common signal output path and in reverse allowing a combined signal having a plurality of different frequency bands to be split into a plurality of signals of different frequency bands. In accordance with another aspect of the present invention, there is provided a method of combining a plurality of signals having different frequency bands, the method comprising:

(1) modifying an xDSL signal to be asymmetric and so converted to a signal wire form transmissible by a signal wire versus ground;

(2) combining the modified xDSL signal with an RF signal to create a combined signal; and

(3) combining the combined signal with a power signal so as to create one signal carrying multiple frequency bands.

Preferably the xDSL signal is a VDSL-2 signal obtained from an optical receiver or optical transceiver.

The method may further comprise combining the power signal with the combined signal using a high pass filter. This ensures no high frequency signal components are added to the combined signal when the power signal is added to the combined signal.

Desirably, the power signal is routed through an impedance matching device before being combined with the combined signal.

The invention will now be described, by way of example, and with reference to the accompanying drawings in which:

Figure 1 shows a signal combining device in accordance with the present invention; Figure 2 shows a detailed view of a power inserting device used within the device of Figure 1 ; and

Figure 3 shows a schematic diagram of the signal combining device in use. Description

Figure 1 shows a signal combining device 10 which has three inputs 12, 14, 16 for receiving signals with different non-overlapping frequency bands and combining those signals into a single signal passing along output path 18 for onward transmission from output 20. First input 12 receives an xDSL signal which is a positive and negative signal. Input 14 receives an RF signal and input 16 receives a power signal. The xDSL signal typically has a frequency range of 300kHz to 30MHz with the power signal typically having a frequency range of DC to 20kHz and the RF signal a frequency range of 85MHz to 1006MHz.

Input 12 is connected to balun or auto -transformer 24 which converts the xDSL signal into an asymmetric signal, i.e. a signal transmitted along a single wire versus ground rather than a signal transmitted on a pair of wires as a positive and negative signal. Output 26 of balun 24 is connected to a low pass side 28 of diplex filter 30 where the converted xDSL signal is combined with the RF signal received at input 14, the RF signal being fed to the high pass side 32 of filter 30.

Balun 24 is made using ferrite transformers for wide band performance. However these types of transformers can have reduced performance at lower and higher frequencies and return loss can be increased in detriment to the overall network. For higher frequencies, some compensation can be achieved by selecting the components in the low pass filter 28 to achieve impedance matching and obtain impedance transformation to gain an improved return loss.

Diplex filter 30 combines the two different frequency signals of RF and xDSL and transmits them along a common signal path 34 whilst maintaining their separate frequency ranges. The combined xDSL and RF signals are then further combined with a power signal from input 16, the power signal being routed through power inserter device 36 to be added to signal path 34 such that output signal path 18 then carries three signals of mutually exclusive frequency bands ready for output.

Power inserter 36 comprises two capacitors and one inductor as shown in detail in Figure 2. For clarity, the second capacitor has been omitted from the representation of the power inserter shown in Figures 1 and 3. Capacitor 40 is an RF path to ground, leaving capacitor 42 and inductor 44 to form a high pass filter. By appropriate selection of the values of these three components, the power inserter acts is arranged to act as an impedance matching device improving the return loss at lower frequencies, typically those below lMHz.

Use of two devices 10, 10' to combine multiple signals having different frequency bands at one end, transmit them along a coaxial cable and split them at the other end into separate signals of different frequency bands is shown in Figure 3. With this arrangement, input 12 receives a VDSL-2 signal from optical transceiver 50 receives data from a cable or broadband supplier. The VDSL-2 signal is converted to be an asymmetric signal using balun 24 and combined with an RF signal received from input 14 by diplex filter 30. A power signal is received at input 16 which powers the optical transceiver. After the three separate frequency band signals are combined on a common signal path, output 20 feeds the combined signal along coaxial cable 52 to a second device 10' which in this instance is used in the opposite sense to split the multiple frequency band signal into three separate signals. For device 10', output 20' now acts as an input, with power inserter 36' and diplex filter 30' separating out the different frequency band signals for separate output. VDSL-2 signal is converted back to a symmetric form by balun 24' and leaves device at outlet 12' to be fed to optical transceiver 50' associated with a user device or user equipment.

By combining RF, xDSL or VDSL-2, and power signals on one coaxial cable, installation of in-home networks is greatly simplified.

Claims

Claims

1. A signal combining device comprising a plurality of inputs, each input connectable to signal paths carrying signals of different frequency ranges and an output connectable to a coaxial cable, wherein first and second inputs form inputs to a combination filter, and a third input is connected to an output of the combination filter to create a combined signal output path, the first input adapted to receive an xDSL signal and a signal conversion device disposed intermediate the first input and the combination filter for converting an xDSL signal to an asymmetric signal.

2. A signal combining device according to claim 1, wherein the xDSL signal is a VDSL-2 signal and the first input is adapted to receive VDSL-2 signals from an optical transceiver.

3. A signal combining device according to claim 1 or claim 2, wherein the signal conversion device is a balun.

4. A signal combining device according to any of the preceding claims, wherein the second and third inputs are connectable to RF signals and power signals respectively.

5. A signal combining device according to any of the preceding claims, wherein the combination filter is a diplex filter, with the first input connected to a low pass side of the diplex filter and the second input connected to a high pass side of the diplex filter.

6. A signal combining device according to any of the preceding claims, wherein the third input is connected to the output of the combination filter by disposing a power inserter device between the third input and the output of the combination filter.

7. A signal combining device according to claim 6, wherein the power inserter comprises capacitive and inductive elements to allow for impedance matching.

8. A method of combining a plurality of signals having different frequency bands, the method comprising:

(1) modifying an xDSL signal to be asymmetric; (2) combining the modified xDSL signal with an RF signal to create a combined signal; and

(3) combining the combined signal with a power signal so as to create one signal carrying multiple frequency bands.

9. A method according to claim 8, wherein the xDSL signal is a VDSL-2 signal.

10. A method according to claim 8 or claim 9, further comprising combining the power signal with the combined signal using a high pass filter.