KR100918015B1 - A device for rebroadcsting and processing a signal and communication network - Google Patents

Abstract

TECHNICAL FIELD The present invention relates to the field of terrestrial digital television, and more particularly, to an apparatus for rebroadcasting a signal 10 composed of at least one digital signal and an analog signal associated with a television program at the same frequency. For example, such a device is used in a residential area to facilitate the reception of digital signals by a portable receiving device. The rebroadcast apparatus according to the present invention comprises: selecting means (11) for protecting an ultra high frequency (UHF) frequency band; Filtering means 12 for removing constant frequencies of the analog signal; Amplifying means (13) for amplifying the filtered signal as described above; It comprises a rebroadcasting means 14 for broadcasting the amplified signal as described above. Eliminating a constant frequency of the analog signal is such that the reception of the analog signals by the receiver rebroadcasts at the same frequency of the signal without perturbation.

Television, gap-filler

Description

A device for rebroadcsting and processing a signal and communication network

1A is a block diagram showing characteristics of a rebroadcast apparatus according to the present invention.

FIG. 1B is a block diagram showing preferred filtering means for the rebroadcast apparatus of FIG. 1A. FIG.

FIG. 2 shows a part of the spectrum of a signal received by the rebroadcast apparatus of FIG. 1A. FIG.

3a schematically illustrates a portion of the spectrum of the main signal 10;
FIG. 3B schematically illustrates the transfer function of three tap filters in series allowing the removal of video carrier frequencies of the three analog components of main signal 10.
FIG. 3C schematically illustrates the spectrum of a signal obtained after filtering by three tap filters in series. FIG.

4 shows the principle of operating the filtering means 12 which also includes means for automatically setting the frequency to be removed.

FIG. 5 illustrates the use of the rebroadcast apparatus of FIG. 1A in a television apparatus. FIG.

The present invention relates to an apparatus for rebroadcasting a signal comprising at least one digital signal associated with a terrestrial digital television program and at least an analog signal associated with a terrestrial analog television program, the analog signal comprising a spectrum comprising a plurality of frequencies. Have

The invention also relates to an apparatus for processing signals for use in such a rebroadcast apparatus.

The invention can be applied, for example, to a home repeater (or called a gap-filler) in terrestrial digital television.

The standard ETS 300744, published by ETSI in March 1997, describes, in particular, DVB-T terrestrial digital television used in Europe. Compared with analog television systems, this system has the advantage of generating a net image when two signals of the same frequency representing the same picture but of different phases are received by the digital signal receiver, whereas analog television Such out-of-phase signals result in a phantom picture resulting in a relatively low quality picture in the analog signal receiver. In digital television, this advantage allows local isochronous rebroadcast of the digital signal received by the receiving antenna via a gap-filler to reach digital signal receivers located relatively far from the receiving antenna. Make it possible. For example, in a dwelling, the digital signal received by the receiving antenna located on the roof of the dwelling may be amplified and re-broadcasted so that a receiver below several floors can receive the signal through the built-in antenna. Nevertheless, such a receiving antenna can receive a relatively large number of signals, in particular digital and analog signals associated with television programs, which are in the same UHF frequency band which is divided into channels. . The term "signal received by the receiving antenna" will hereinafter be referred to as an assembly of signals received from the receiving antenna, in particular digital and analog signals associated with a television. When the signal received by the receive antenna is amplified and rebroadcasted, the analog signal in the signal received by the receive antenna will be amplified and rebroadcasted. Now the analog signal cannot be rebroadcast at the same frequency without the risk of phantom pictures. This is because when the rebroadcast analog signal and the analog signal received by the receiving antenna occur at the analog signal receiver, the rebroadcast analog signal is out of phase with respect to the analog signal received by the receiving antenna. As a result, it is necessary to eliminate the analog signal received by the antenna prior to the rebroadcast of the signal, in order for local dynamic frequency rebroadcast not to confuse users of analog signal receivers. The contemplated solution is to filter, by band pass filters, the signal received by the receiving antenna in the UHF frequency band so as to preserve only the digital signal. Such a solution has the disadvantage that UHF channels used in digital television are generally close to existing analog channels, which suggests that the required bandpass filters must be relatively selective and thereby complicated. To solve this problem, it has been considered to perform frequency conversion on the signal received by the receiving antenna, which causes less selectivity of the filters. This solution has been particularly adopted for the gap filler sold by Tekotelecom (web page: http://tekotelecom.it/products/dvbt/dvbrp.htm). Nevertheless, such frequency conversion requires relatively stable and consequently complicated oscillators, which leads to relatively high cost.

It is an object of the present invention to provide a rebroadcast apparatus which can be carried out in a simple manner and as a result can be carried out at a relatively low cost.

As defined at the outset, the rebroadcast apparatus according to the present invention is:

Selection means suitable for preserving frequency bands corresponding to the digital signal and the analog signal;

Filtering means suitable for removing at least one frequency from the plurality of frequencies, preserving at least one of the plurality of frequencies, and supplying a filtered signal;

Amplification means suitable for amplifying the filtered signal and for supplying an amplified signal;

Rebroadcasting means suitable for broadcasting the amplified signal.

The present invention benefits from the fact that the spectrum of the analog signal includes certain frequencies that can be rebroadcast without perturbing the reception quality by the analog signal receiver. This is especially the case with sound carrier frequencies that do not produce perceptible perturbation when rebroadcast. The signal received by the receiving antenna is first filtered by the selection means to preserve the UHF frequency band. The filtering means then removes frequencies which cause perturbations in the analog signal receiver when rebroadcast. The resulting filtered signal is then amplified and rebroadcast to reach digital signal receivers located relatively far from the receiving antenna.

The rebroadcast apparatus as described above is preferably characterized in that said plurality of frequencies comprises at least a video carrier frequency and said filtering means comprises removal means suitable for removing video carrier frequencies or frequencies in said spectrum. .

Indeed, relatively large perturbations are caused by the video carrier frequencies when the video carrier frequencies are rebroadcast for reception by the analog signal receiver, while other frequencies of the analog signals cause less problems.

In a variant, said means for removing comprises a number of tap filters equal to the number of video carrier frequencies in said spectrum, said tap filters being configured in series, each of which being equal to one of the video carrier frequencies. It has a different rejection frequency.

According to this variant, a limited serial configuration of tap filters is used to filter the signal received by the receiving antenna, which results in a relatively simple and low cost rebroadcast device.

In addition, the filtering means also preferably comprise means for controlling the frequency or frequencies to be removed. The frequencies to be removed can thus be controlled as a function of the geographical area in which the rebroadcast device is installed. Thus, such a rebroadcast apparatus can be used in all geographical regions where DVB-T type digital signals are present near the analog signal.

In a variant, the control means comprises means for automatically setting the frequency or frequencies to be removed. Frequencies that are effectively removed by the filtering means correspond to the frequencies that are desired to be removed. One of the advantages of such setting means is that even when derivatives of certain electronic components of the control means exist, the removed frequencies still remain as frequencies to be removed.

The frequencies are effectively removed by filtering means corresponding to the frequencies that are desired to be removed. One of the advantages of such setting means, which is derived in the constant electronic components of the control means, is to remove the frequencies still remaining in the removed signals.

Other aspects than the above of the present invention are apparent from the embodiments described below, and will be described with reference to the embodiments.

1A illustrates a rebroadcast apparatus according to the present invention. Such a rebroadcast apparatus comprises a selecting means 11, a filtering means 12, an amplifying means 12, and a rebroadcasting means 14. The main signal 10 received by the receiving antenna is filtered by the selecting means 11 such that a part of the main signal 10 is preserved in the UHF frequency band. In fact, in addition to the frequencies of the UHF band, the main signal 10 includes supplementary frequencies corresponding to, for example, FM broadcast or GSM telecommunications. Since amplification and rebroadcast of such auxiliary frequencies is undesirable, it is desirable to eliminate such signals by the selection means 11, which may be a band pass filter for the UHF frequency band between 470 MHz and 860 MHz. The filtered main signal 10 is then filtered by the filtering means 12 such that the rebroadcast removes the frequencies that cause perturbation in the picture displayed by the analog signal receiver. The obtained signal is then amplified by the amplifying means 13 and then rebroadcast by the rebroadcasting means 14.

1b shows a filtering means 12 according to a preferred embodiment of the invention. Such filtering means 12 comprise six tap filters numbered 120 to 125 with respective reject frequencies, each having a rejection frequency. The example considered here can be applied to the geographical area in France, for example, where six analog channels are used for broadcast analog television programs and each of these channels has a video carrier frequency.

There are geographic areas where the number of analog channels used is not six. In this case, the number of tap filters to be used in the filtering means 12 is equal to the number of analog channels used. Each tap filter is controlled to remove a given video carrier frequency. That is, the rejection frequency of the tap filter 120 is equal to the video carrier frequency of the first channel used, and the cutoff frequency of the tap filter 121 is equal to the video carrier frequency of the second channel used. The series connection of the six tap filters 120 to 125 thus enables the removal of all video carrier frequencies of the analog signal received by the receiving antenna.

For example, it applies to a geographic location, such as France, where there are six analog channels using analog television programs that are re-broadcast and each of those channels having an image carrier frequency. There are geographic locations with the number of analog channels used differently from the six. In this case, the number of tap filters used in the filtering means 12 is equal to the number of channels used for the analog channels. Each tap filter controls the removal of a given image carrier frequency, that is, the rejection frequency of tap filter 120 is equal to the frequency of the first channel used, and the cutoff frequency of tap filter 121 is equal to the two used. It is the same as the image carrier frequency of the first channel. The six tap filter series of 120 to 125 allow to remove all image carrier frequencies of the analog signal received from the receiving antenna.

2 shows a portion of the spectrum of the main signal 20, including analog and digital signals. This part represents the frequency band corresponding to three adjacent channels. The first digital component 23 is broadcast over the first channel 20. The analog component 24 is broadcast on the second channel 21. The second digital component 25 is broadcast over the third channel 22. The analog component is the "analog signal" is the set of analog components in the UHF frequency band of the main signal 120, and the "digital signal" is the set of digital components in the UHF frequency band, where the analog It should be noted that the signal corresponds to a television program and that the digital component may correspond to several television programs. The analog component 24 has a video carrier frequency 26, a chrominance carrier frequency 27, and an acoustic carrier frequency 28. The channel matches the spectral width of 8 MHz. The spectral width, i.e., the frequency difference between the acoustic carrier frequency 28 and the second digital component 25, has a value of about 0.25 MHz, which means that if one wants to fill the main signal 10 to preserve only the digital signal, there is a relatively separated sensitivity. Requires a good filter The spectral width between video carrier frequency 26 and first digital component 23 has a value of about 1.25 MHz. In conclusion, the fact that video carrier frequency 26 is removed alone requires a somewhat lower separation sensitivity and a somewhat lower cost filter.

3A schematically illustrates a portion of the spectrum of the main signal 10. A portion of the spectrum consists of twelve channels 301-312. Channels 301, 303, 304, 307, 309, 310, and 312 are digital channels. Channels 302, 305, 311 are analog channels. Channels 306 and 308 are not used. In the main signal 10 the analog components of the analog signal are each broadcast on an analog channel. Each analog component has frequencies plotted in the manner of a vertical line, video carrier frequency, chrominance carrier frequency, and acoustic carrier frequency.

3b schematically illustrates the transfer function of three tap filters in series allowing the removal of video carrier frequencies of the three analog components of main signal 10. The rejection frequency of the first tap filter is the same as the video carrier frequency of the analog component broadcast on channel 302, the rejection frequency of the second tap filter is the same as the video carrier frequency of the analog component broadcast on channel 305, and the third The rejection frequency of the tap filter is equal to the video carrier frequency of the analog component broadcast on channel 311. It is possible to use a filter with an adjustable rejection frequency. These filters include variable capacitances that may be changed in the manner of potencymeters, such as adjusting the rejection frequency, for example. It is also possible to use a filter of the rejection frequency which is adjusted via the graphical interface. According to the invention, the rebroadcast apparatus can be connected to the graphical interface in the form of a screen or a keyboard, for example. While such a rebroadcast device is installed, the operator injects video carrier frequencies of the analog signal inherently in a geographic location using a keyboard, such as adjusting each rejection frequency to one of the video carrier frequencies.

3C schematically shows the spectrum of the signal obtained after being filtered by three tap filters in series. Three video carrier frequencies have disappeared. For example, it should be noted that it is possible to remove other frequencies of analog components in the same way at chrominance frequencies if necessary. In this case, it is advisable to add another tap filter with the same reject frequencies as other frequencies to be removed.

4 shows the principle of operating the filtering means 12 which also includes means for automatically setting the frequency to be removed. Such filtering means comprises six tap filters listed from 120 to 125, six D / A converters listed from 420 to 425, a shunt 400 and a tuning frequency controlled by the microcontroller 408. Local oscillator 402, mixer 403, bandpass filter 404 having a narrow band tuned to intermediate frequencies, amplifier 405, detector 406, and A / D converter 407. It consists of. The example considered here applies to the geographic area where six analog channels are used. Each tap filter 120-125 includes a variable capacitor that serves to supply these variable capacitors with a DC voltage to allow modification of the rejection frequency. For example, in tap filter 120, this DC voltage is obtained by a command from microcontroller 408 via D / A converter 420. Signal 410 is filtered by a series of tap filters 120-125 to supply filtered signal 411. If the installer wants to control the tap filter 120 to remove the video carrier frequency of the first analog channel of the signal 410, the installer may then video the microcontroller 408 via a graphical interface, for example. Supply the value of the carrier frequency. The microcontroller 408 instructs the D / A converter 420 to supply a DC voltage to adjust the rejection frequency of the tap filter 120 to the video carrier frequency. Nevertheless, because of a number of parameters, such as drifts of variable capacitors, the frequency effectively rejected by tap filter 120 is not exactly the same as the video carrier frequency being removed. The following principle alleviates this drawback. For example, the shunt 400 occupies one hundredth of the power of the filtered signal 411. The microcontroller 408 instructs the local oscillator 402 to adjust its tuning frequency to the difference between the video carrier frequency indicated by the installer and the intermediate frequency of the band pass filter 404. A portion of the filtered signal 411 taken by the shunt 400 passes successfully through the mixer 403, the band pass filter 404, the amplifier 405, and the detector 406. The residual level at the output of detector 406 is obtained, which is represented by the voltage of the video carrier frequency being removed. If the rejection frequency of the tap filter 120 is close to the video carrier frequency, this residual level will be relatively low. However, if this rejection frequency is far from the video carrier frequency, the residual level will be relatively high. As a result, this residual level is minimal when the reject frequency is closest to the video carrier frequency from which it is removed. The microcontroller 408 sends a command to the D / A converter 420 so that the supplied DC voltage changes until the residual level at the output of the A / D converter 407 becomes minimum. The DC voltage obtained when the residual level is minimum is then stored in a memory (not shown) of the microcontroller. For example, it should be noted that such adjustments may be performed multiple times, considering the drifts of the variable capacitors once a month. Nevertheless, only the adjustments made initially require interference by the installer. The adjustment of the other tap filters 121-125 is performed in the same way by indicating the video frequency to be removed in each adjustment.

5 illustrates the use of rebroadcast devices in a television system. Such a television system includes a transmitting antenna 501, a receiving antenna 502, four rebroadcasting devices 503 to 506, four digital signal receivers 507 to 510, and two analogues. Signal receivers 511, 512. Receive antenna 502 receives signals transmitted from transmit antenna 501 and possibly other neighbor transmitters. In particular, signals received from the receive antenna include digital and analog signals related to television programs. In this example under consideration, the rebroadcast device is installed on each floor of the house 513. For example, other arrangements for installing a single rebroadcast device for the entire house 513 or a single signal processing device in accordance with the present invention coupled to multiple rebroadcast antennas may be considered. Configurations that can be considered depend on a number of parameters such as, for example, the size of the house 513 or the structural materials. The four rebroadcast devices 503-506 are shown in bold straight lines in this figure and receive signals from the receive antenna 502 via a cable commonly used to transmit analog signals received by the receive antenna 502. . The two analog signal receivers 511 and 512 are connected to the receiving antenna by the same cable. By virtue of the filtering device of the rebroadcasting devices 503 to 506 according to the present invention, the image displayed by the two analog signal receivers 511, 512 is subjected to the same frequency rebroadcast of the signal received by the receiving antenna 502. Not disturbed by

The above description with reference to the drawings is intended to illustrate rather than limit the invention. In this regard, several points of reference are given below.

For example, the description of the drawings applies to the DVB-T standard described in the ETS 300744 standard. The present invention applies to other digital television standards that can be further improved because digital signals and analog signals coexist and co-frequency rebroadcast of digital signals is possible without disturbing the pictures corresponding to these digital signals.

The television system is described with reference to FIG. It is possible to deviate from this manner without departing from the scope of the present invention. For example, the rebroadcast device may be installed in a home that may include several digital signal receivers. The rebroadcast device may also serve as a relay device for transmitting digital signals in a geographic area with poor service of the transmit antenna 501, for example due to such obstacles as mountains. In such a case, the rebroadcast apparatus may be installed in the secondary antenna.

The rebroadcast apparatus according to the present invention may be used in a communication network including at least a transmitter capable of transmitting signals representing an image, a transmission network, and a receiver capable of receiving the signals.

The use of the verb "comprises" and its use does not exclude the presence of components other than those described in the claims. Singular expressions used before a component do not exclude the presence of a plurality of such components.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the field of terrestrial digital television, and more particularly, to an apparatus for re-broadcasting a signal 10 composed of at least one digital signal and an analog signal related to a television program at the same frequency. The effect is that the reception of analog signals by the receiver is rebroadcasted at the same frequency of the signal without perturbation.

Claims (11)

Device for signal rebroadcasting, Digital signals related to at least terrestrial digital television programs, 10. An apparatus for re-broadcasting a signal comprising at least an analog signal relating to a terrestrial analog television program, the analog signal having at least the analog signal having a spectrum comprising a plurality of frequencies. Selection means for preserving frequency bands corresponding to the digital signal and the analog signal;     Filtering means for removing at least one frequency from the plurality of frequencies, preserving at least one of the plurality of frequencies, and supplying a filtered signal; Amplifying means for amplifying the filtered signal and supplying the amplified signal; And at least rebroadcast means for broadcasting said amplified signal. The method of claim 1, The plurality of frequencies comprises at least a video carrier frequency, And the filtering means removes the video carrier frequency or frequencies in the spectrum. The method of claim 2, The filtering means comprises a number of tap filters equal to the number of video carrier frequencies in the spectrum, the tap filters configured in series, each of the tap filters being one of the video carrier frequencies. Apparatus for signal rebroadcast, characterized by having the same different rejection frequency. delete delete Apparatus for signal processing, Input means for receiving at least a digital signal relating to a terrestrial digital television program; An input means for receiving at least an analog signal related to a terrestrial analog television program, said analog signal comprising input means for receiving said analog signal, said spectrum having a spectrum comprising a plurality of frequencies, wherein said signal processing apparatus comprises: The processing apparatus supplies filtering means for removing at least one frequency from the plurality of frequencies, preserving at least one of the plurality of frequencies, and thereby generating a filtered signal, and the filtered signal. And an output means for outputting said device. delete The method of claim 6, The filtering means comprises a number of tap filters equal to the number of video carrier frequencies in the spectrum, the tap filters configured in series, each of the tap filters having a different rejection frequency equal to one of the video carrier frequencies. The signal processing apparatus characterized by having. delete delete In a communication network, At least a transmitter capable of transmitting signals representing at least an image, a transmission network, a receiver capable of receiving the signals, and at least a rebroadcast apparatus as claimed in claim 1.

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