Patent Application
20080222683
The present invention generally relates to the field of TV-signal distribution systems for multiple dwelling units. More particularly, the invention relates to a system of cascadable TV-signal distribution units, a unit as part of such a system and a method for installing such a system.
Multiple dwelling units (MDU) are systems where typically the satellite IF-band and terrestrial cable are distributed over different apartments or flats or the like. This can be done by the use of multiswitches, by the use of taps, such as for example described in EP 1 347 644 A2, or any other distributing devices known to the person skilled in the art. In the case of the multiswitches, it means that the signals coming from the head end (mostly on the roof) will be distributed over the whole building by cascading an amount of multiswitches. Typically, they will be installed inside the technical shaft of the building, and at each floor, customer drops will be tapped off to provide signals to the end-users. This is shown in
In all applications where multiswitches or other “cascadable units” are used, it is clear that a professional installation is needed. If the first units are not well tuned, it may affect the whole system. Therefore, the installer needs to use expensive measurement equipment for fine-tuning the system.
Nowadays, the installer more and more uses specialized software which takes into account a lot of parameters of the system, like carrier-to-noise, power and distortion, gain/loss, etc. to calculate the whole system in advance. However, this software is still based on assumptions, for instance what is the output level of the head end, what is the loss of the interconnecting coaxial cables, etc. In reality, the characteristics of the installed system usually differ from the assumed values, so the installed system still needs to be checked in the field. Consequently, the software does not relieve the installer from needing expensive measurement equipment.
It is an aim of the present invention to provide a system of cascadable TV-signal distribution units which can be installed more easily.
This aim is achieved according to the invention with a system showing the technical characteristics of the first claim.
It is also an aim of the present invention to provide a more efficient method for installing a system of cascadable TV-signal distribution units.
This aim is achieved according to the invention with a method comprising the steps of claim 11.
As used herein, “TV-signal” is intended to mean any signal at any frequency which carries TV images, whether aerial or terrestrial.
As used herein, by “vertical lines” is not intended that the lines necessarily extend in vertical direction. This is just the term which is used in the art since the lines for transporting signals usually extend from a head end on the roof up to for example a multiswitch for the flats on the ground floor.
As used herein, by “horizontal lines” is not intended that the lines necessarily extend in horizontal direction. This is just the term which is used in the art for the lines which are branched off from the vertical lines to for example connect a customer to a multiswitch.
As used herein, with “cascadable unit” is meant any TV-signal distribution unit which is installed on one or more vertical lines of a TV-signal distribution system.
The system of the invention comprises a plurality of groups of one or more TV-signal distribution units, i.e. cascadable units which are connected on the vertical lines and/or other units which are connected on the horizontal lines. Each TV-signal distribution unit comprises a plurality of lines on which input signals coming from a head end are transported from an input side to an output side of the unit. According to the invention, at least one of the TV-signal distribution units of each group has the following features:
at least one measurement means on each of the lines for measuring a signal characteristic of a TV-signal transported on that line,
a programmable processing means connected to the measurement means and provided for comparing each of the measured signal characteristics with at least one programmable reference value and determining a signal quality from each comparison,
indicator means connected to said programmable processing means and provided for indicating each of said signal qualities to an installer of the system.
In other words, a group of the system of the invention can for example comprise one TV-signal distribution unit having the measurement, processing and indicator means and one TV-signal distribution unit not having these means. A group can also be formed by only one TV-signal distribution unit which has the measurement, processing and indicator means. In general, each group comprises at least one TV-signal distribution unit having the measurement, processing and indicator means and possibly one or more TV-signal distribution units not having these means.
The programmable reference value or values can be programmed into each of the TV-signal distribution units at the factory and/or in the field. The units may also be reprogrammable, so that adjustments can be made later on.
By means of the indicator means, the installer is thus informed whether or not the transported signal on each of the lines has the required signal quality, which is programmed into the processing means by the programmable reference value. If the indicated signal quality is as required, no problems are to be expected and no adjustments are considered necessary. If the indicated quality does not meet the requirements, an adjustment is considered necessary to avoid problems.
With the TV-signal distribution units of the invention, the signal quality on each of the lines can be indicated towards the installer throughout the system without needing expensive measurement equipment. Such equipment is as it were incorporated into one or more TV-signal distribution units of each group. In this way, the installer is instantly informed where the signal quality does not meet the requirements and can immediately make the necessary adjustments to the system such as placement of an amplifier/attenuator between given stages of the cascade, thus saving time. The TV-signal distribution units of the invention can also obviate the need for calculation of the system in advance, since problems can be dealt with immediately in the field.
In one embodiment, the programmable processing means is provided for determining for each line whether the signal quality of the transported signal is “suitable” or “unsuitable” for distribution towards the end-users. In this embodiment, the programmable processing means for example determines the signal quality by checking if the measurement value is above or below the programmable reference value. Both qualities “suitable” and “unsuitable” can be subdivided in different values to provide further information.
The TV-signal distribution units of the system of the invention preferably themselves comprise adjustment means for adjusting the signal characteristic, which is measured by the measurement means, of the signal transported on at least one of the lines. The programmable processing means may be provided for controlling these adjustment means, so that the units are self-adjusting, and/or they may be accessible towards the installer for adjustments.
The system of the invention can further comprise one or more intermediate units for installation between the output side of one TV-signal distribution unit and the input side of another TV-signal distribution unit. This intermediate unit comprises adjustment means for adjusting the signal characteristic, which is measured in the TV-signal distribution units, of the signal on at least one of the lines. The intermediate unit can be placed where necessary, i.e. if the signal quality on the output side of a TV-signal distribution unit cannot be adjusted on that TV-signal distribution unit to meet the requirements. The intermediate unit is then placed and the adjustment is made until the requirements are met. The intermediate units may also comprise the measurement means, the programmable processing means and the indicator means in the same way as the other TV-signal distribution units.
The number of lines of each of the TV-signal distribution units can for example be from the range of 1 terrestrial input combined with 2, 4, 8, 12 or 16 satellite IF inputs. Any other number of lines is however also possible.
In a preferred embodiment, the measurement means which are provided on each of the lines of the TV-signal distribution units comprise a signal level measurement instrument. In this embodiment, the programmable processing means compare the measured signal levels with pre-programmed lower and upper reference values, to verify whether the signal level on the respective line is inside or outside a given window. In this way, the processing means deliver a signal quality “unsuitable”, with the subdivision into “too weak” or “too strong” or a signal quality “suitable”, meaning the signal level is within the pre-programmed window. The indicator means are preferably provided to indicate each of these possible values to the installer. This can for example be done by means of LEDs of different colours, but other indicator means are possible, such as for example an analog readout, an LCD or a light display, beep signals or any other visual or auditive indicator means known to the person skilled in the art.
In case the measured characteristic is the signal level as in the above embodiment, the intermediate unit comprises for example an amplifier/attenuator with an amplifying/attenuating circuit for amplifying/attenuating the signal level of at least one of the signals on the lines. The amplifier/attenuator can be provided with individual amplifying/attenuating circuits for each of the lines, so that the level of each of the lines can be controlled individually. Alternatively, separate amplifiers/attenuators for each line or groups of lines can be used. Any other intermediate units for adapting the signal level are also possible.
Using the above described system of TV-signal distribution units, the installation of the system becomes very simple. The installation method according to the invention comprises the following steps:
a) installing a group of TV-signal distribution units by connecting the input side of an uppermost TV-signal distribution unit of the group to lines for transporting TV-signals originating from a head end and subsequently connecting any other TV-signal distribution units of the group in cascade on the output side of the uppermost TV-signal distribution unit,
b) checking the signal quality on each of the lines by means of the indicator means of any of the TV-signal distribution units of the installed group,
c) where necessary, installing an intermediate unit before the uppermost TV-signal distribution unit of the group and/or in between two TV-signal distribution units of the group, the intermediate unit comprising adjustment means for adjusting the signal characteristic which is measured by the measurement means,
d) on the lines where necessary, adjusting the signal characteristic by means of the adjustment means of the installed intermediate unit and/or adjustment means of the TV-signal distribution units.
For the sake of clarity, it is repeated that a group of TV-signal distribution units according to the invention can for example comprise one TV-signal distribution unit having the measurement, processing and indicator means and one TV-signal distribution unit not having these means. A group can also be formed by only one TV-signal distribution unit which has the measurement, processing and indicator means. In general, each group comprises at least one TV-signal distribution unit having the measurement, processing and indicator means and possibly one or more TV-signal distribution units not having these means.
Steps a) to d) can be repeated for each subsequent group of TV-signal distribution units. The installer has the options of installing all groups at once and only afterwards installing the intermediate units where necessary or, more efficiently, installing the groups one by one, each time checking the indicator means of the group once it is installed and installing an intermediate unit before the group if necessary.
As each group has at least one TV-signal distribution unit which can immediately indicate when the signal quality does not meet the requirements, the installer is immediately aware of the problem and its location in the whole system. As a result, he can immediately install the appropriate intermediate unit on the most appropriate location.
It is preferred that each group comprises only a single TV-signal distribution unit, this unit then being one with the indicator means. In this way, optimal hardware efficiency can be achieved, since the intermediate units can now be placed only before the TV-signal distribution units where the signal quality would otherwise be insufficient. This can reduce the number of intermediate units which are installed in the system. However, groups of for example two TV-signal distribution units of which only one has the indicator means are also possible. In such a system, however, it may for example occur that an intermediate unit is placed before a TV-signal distribution unit without indicator means, whereas the signal quality on this unit would still be sufficient.
In a second aspect of the invention, it is an aim to provide a signal degradation compensation system with improved compensation capabilities. In the following, this second aspect will be briefly described.
The signal degradation compensation system of the invention comprises the following features:
at least one line for transporting a TV-signal from an input side to an output side,
measurement means on each of the lines for measuring at least two signal characteristics of the TV-signal on that line,
a programmable processing means connected to the measurement means and provided for comparing the measured signal characteristics with corresponding programmable reference values and determining a signal quality from each comparison,
signal degradation compensation means on each of the lines, connected to said programmable processing means and provided for compensating degradation of the transported TV-signal on the basis of the signal qualities determined by the programmable processing means.
In a preferred embodiment, the signal degradation compensation means are located upstream of the measurement means. This has the advantage that the programmable processing means is provided with feedback on the compensation.
In one embodiment of the signal degradation compensation system of the invention, the unit further comprises a user interface with indicator means for indicating each signal quality to an installer and control means by means of which the installer can control the signal degradation compensation means. The indicator and control means can be anything which is deemed suitable by the person skilled in the art, such as for example LEDs of different colours, an analog readout, an LCD or a light display, beep signals or any other visual or auditive indicator means. With this embodiment, the installer himself derives the necessary compensation from the information which is presented to him on the indicator means. The fact that the signal degradation compensation means are preferably upstream from the measurement means has the consequence that the installer gets feedback on his compensation, so that a correct compensation can be ensured.
The TV-signal degradation compensation system of the invention can be carried out as a single unit which incorporates the measurement means, the programmable processing means, as well as the signal degradation compensation means or as separate units, namely a measurement unit incorporating the measurement means and the programmable processing means and a compensation unit incorporating the signal degradation compensation means. In the latter case, the compensation unit can be mounted further upstream from the measurement unit to keep the number of devices in the dwelling of the end-user at a minimum.
In the case of a single unit, the programmable processing means can be further provided for interpreting the derived signal qualities and accordingly controlling the signal degradation compensation means. This embodiment has the advantage of automatic compensation of the signal degradation. The fact that the signal degradation compensation means are preferably upstream from the measurement means has the consequence that the processing means gets feedback on the performed compensation, so that a correct compensation can be ensured.
This second aspect of the invention can be applied on the “vertical lines”, as have been described above, as well as on “horizontal lines”, i.e. the so-called “customer drops” which branch off from vertical lines. Again, these “horizontal lines” do not necessarily extend in horizontal direction. In other words, the signal degradation compensation unit can be a TV-signal distribution unit or an intermediate unit as have been described above, or any unit downstream from the TV-signal distribution units on the horizontal lines.
Preferably, each of the determined signal qualities comprises at least values which are indicative of the transported signal being “suitable” or “unsuitable” for distribution towards end-users. The “suitable” or “unsuitable” signal quality means that the installer or the processing means is informed whether or not the measured signal quality meets the requirements, which are programmed into the processing means by the programmable reference values. If the quality is “suitable”, no compensations are considered necessary. If the quality is “unsuitable”, compensation is considered necessary. Both qualities “suitable” and “unsuitable” can be subdivided in different values to provide further information.
In a preferred embodiment of the signal degradation compensation system of the invention, the measurement means are provided for measuring the signal level on at least two spaced apart frequencies within the bandwidth of the signal. Since the signal level typically has a linear variation over the bandwidth, the processing means can determine the signal level over the whole bandwidth of the signal from the two or more measurements of the signal level on the spaced apart frequencies. A negative slope in the signal level indicates degradation, so an appropriate compensation can be a slope adjustment, as well as a gain adjustment if the overall signal is too weak.
The invention will be further elucidated by means of the following description and the appended figures.
The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. The dimensions and the relative dimensions do not necessarily correspond to actual reductions to practice of the invention.
Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. The terms are interchangeable under appropriate circumstances and the embodiments of the invention can operate in other sequences than described or illustrated herein.
Moreover, the terms top, bottom, over, under and the like in the description and the claims are used for descriptive purposes and not necessarily for describing relative positions. The terms so used are interchangeable under appropriate circumstances and the embodiments of the invention described herein can operate in other orientations than described or illustrated herein.
The term “comprising”, used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It needs to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression “a device comprising means A and B” should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.
In the following, preferred embodiments of the invention will be described in which the signal characteristic which is measured is the signal level. The invention can however also be applied to measure and adjust any other signal characteristic. The idea of these preferred embodiments is to indicate in a visual manner what the levels are at certain points of the installation, for instance the level at each interconnection between the cascadable units can be visualized. As mostly several level indicators will be installed, this gives a simple overview of the whole system in the blink of an eye.
In the following, the invention will be mainly described in a system comprising a plurality of cascadable TV-signal distribution units connected on vertical lines originating from a head end. It is clear the invention can also be applied in units on the horizontal lines, or in units on both the horizontal and vertical lines.
The typical prior art system of
The system of
The cascadable unit 10 of
With the system of
Alternatively, the installation can also be performed by installing the cascadable units 10, 12, 14 one by one, checking the signal levels and making the necessary adjustments if necessary before installing the next cascadable unit. In this case, each cascadable unit on its own forms a group in the wording of the invention.
Another possible embodiment of the present invention is based on other existing products of Unitron, where the cascading principle is present as well, such as for example the SCU-2P3MDC, the SCU-4P5MTB, or other cascadable units. The cascadable unit 30 shown in
The present invention is applied in the stacker 30 as follows. The detection circuit 32 of the AGC can act as the measurement means, as described in the disclosure of the invention. Each of the AGCs outputs a voltage which is a representation of the signal level at each input 35, 36. This representation can be linear but does not need to be, it can even be inverse, meaning the higher the signal level, the smaller the voltage. Next, this voltage can be fed into the microcontroller 33 of the AGC, which can be programmed by the manufacturer to decide if the signal level falls within a given window. In this example, the decision on the colour of the LEDs 31 can for instance be:
The system of
In
As the first stacker has a too high signal level, the first action of the installer should be to reduce this input level, coming from the head end 51. This can for instance be done by placing an attenuator 59 of for example 5 dB on each vertical line 54 coming from the head end 51, as shown in
As appears from the above, it is important that the installer follows the direction of the signal, this means he first has to look at the LEDs of the first cascadable unit near the head end. And only when those are green, he can look at the second unit and act according the colour of these LEDs. As soon as also these LEDs are green, he can go to the next unit and so on. If he executes this algorithm until the last unit, the result will be a “calibrated system” with optimal, i.e. the least possible hardware usage.
In the above explanation of the calibration system of
A small enhancement could be reached if the installer is educated to find the level where the LEDs are just not red, but green. This means the level at this point is just below the “too high” level. In this way, the maximum number of cascadable units can be connected without need of a next intermediate unit. This is the case if the cascadable units have insertion loss on the vertical lines. If they would have gain, then, depending on the length of the cable, it could be more useful to aim for the lowest part of the green window.
The present invention can also be based on 1 limit instead of 2 limits, for instance by defining only an upper limit for the signal level. In this case, the blinking red is eliminated, and the installer can only detect if the signal is too strong. The same can be worked out with only the red blinking lower limit.
In the cascadable units, a different amount of indicators can be implemented with respect to the amount of “vertical” lines. LEDs can be multiplexed or maybe some lines are not useful to be calibrated, like the terrestrial path in some cases.
Instead of incorporating the indicators inside the cascadable units, these indicators can also be designed as add-on products, only being inserted inside the system during installation. This could save costs as 1 indicator device can then serve several installations.
The invention can also be used on the horizontal lines, acting as customer drops. A similar principle for detecting levels by a level indicator can be implemented. Implementing the invention in the horizontal lines can be treated in the same way as in the previously described vertical lines. So this will not be discussed in detail.
In the following, an enhanced embodiment of the invention will be described with reference to
For the explanation, the situation of
For optimal performance, the centre frequencies are chosen apart as far as possible, meaning the first LED 76 is preferably indicating the level at the lowest frequency of the amplified band, while the second LED 77 indicates the level of the highest frequency of the amplified band. Again a window can be assigned to the two LEDs 76, 77. In the horizontal lines, other windows may be more appropriate than in the vertical lines, but this is a matter of choice and circumstances. A suitable window can for example be:
As mentioned, during installation of the customer drops with their distribution system, problems can appear with levels and slopes of the wideband signals. A typical customer drop can include 10 m of cable, an 8-way splitter, again 10 m of cable, a next 8-way splitter and 30 m of cable before entering the customer premises to be connected with the customer device (de-stacker). With this 50 m of cable, a slope of more than 20 dB can be induced in some cases. With this typical customer drop, each cascadable unit is able to provide signal to 64 customers. The compensation unit 70 with 2 LEDs can now for instance be installed just before the last 8-way splitter, like in
The system connected on the horizontal line can for example be calibrated as follows.
If the signal cannot be adjusted by means of a single compensation unit 70, i.e. it is not possible to adjust such that both LEDs 76, 77 become green, the cause can be that the signal has degraded too much by the use of for example cheaper or bad performing adjustable amplifiers. In such a case, an iteration of two or more compensation units 70 can be used to solve the problem.
In alternative embodiments of signal degradation compensation devices or systems, other compensation circuitry may be used so that the calibration technique also becomes different. Furthermore, the compensation circuitry itself may be included in a separate unit from the unit with the measurement circuitry, the microcontroller and the indicators.
In the embodiment of
Not only the horizontal lines can have units with multiple LEDs per line, also the vertical lines can be equipped with units which detect not only the level of one band, but also the slope, or other signal characteristics. With similar amplifiers, with adjustable gain and slope, also the vertical lines could be compensated for gain and slope.
As the window of the LED colour can be (re-)programmed independently for the two LEDs 76, 77 of the compensation unit 70, the window for each LED can be set differently. This could be necessary if a long cable is expected behind the compensation unit 70. In this case, it can be advisable to set the window for the lowest band lower than the window for the highest band. For instance a difference of 5 dB could be set, which would allow to compensate for an extra 10 or 15 m of cable (depending on the type of cable and the frequency range of the wideband signal).
The compensation unit 80 of
| Number | Date | Country | Kind |
|---|---|---|---|
| 05106540.7 | Jul 2005 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP06/64341 | 7/17/2006 | WO | 00 | 3/10/2008 |
