WO2009016475A2 - Process for analysing an analogue/digital terrestrial and/or cable television signal and related apparatus - Google Patents

Process for analysing an analogue/digital terrestrial and/or cable television signal and related apparatus Download PDF

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Publication number
WO2009016475A2
WO2009016475A2 PCT/IB2008/001983 IB2008001983W WO2009016475A2 WO 2009016475 A2 WO2009016475 A2 WO 2009016475A2 IB 2008001983 W IB2008001983 W IB 2008001983W WO 2009016475 A2 WO2009016475 A2 WO 2009016475A2
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WO
WIPO (PCT)
Prior art keywords
signal
process according
mhz
frequency
digital
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Application number
PCT/IB2008/001983
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French (fr)
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WO2009016475A3 (en
Inventor
Edoardo Romano
Original Assignee
Ro.Ve.R. Laboratories S.P.A.
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Application filed by Ro.Ve.R. Laboratories S.P.A. filed Critical Ro.Ve.R. Laboratories S.P.A.
Publication of WO2009016475A2 publication Critical patent/WO2009016475A2/en
Publication of WO2009016475A3 publication Critical patent/WO2009016475A3/en

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04H—BROADCAST COMMUNICATION
    • H04H20/00—Arrangements for broadcast or for distribution combined with broadcast
    • H04H20/12—Arrangements for observation, testing or troubleshooting
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
    • H04N21/43—Processing of content or additional data, e.g. demultiplexing additional data from a digital video stream; Elementary client operations, e.g. monitoring of home network or synchronising decoder's clock; Client middleware
    • H04N21/438—Interfacing the downstream path of the transmission network originating from a server, e.g. retrieving encoded video stream packets from an IP network
    • H04N21/4383—Accessing a communication channel
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
    • H04N21/43—Processing of content or additional data, e.g. demultiplexing additional data from a digital video stream; Elementary client operations, e.g. monitoring of home network or synchronising decoder's clock; Client middleware
    • H04N21/442—Monitoring of processes or resources, e.g. detecting the failure of a recording device, monitoring the downstream bandwidth, the number of times a movie has been viewed, the storage space available from the internal hard disk
    • H04N21/44209—Monitoring of downstream path of the transmission network originating from a server, e.g. bandwidth variations of a wireless network
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04H—BROADCAST COMMUNICATION
    • H04H60/00—Arrangements for broadcast applications with a direct linking to broadcast information or broadcast space-time; Broadcast-related systems
    • H04H60/35—Arrangements for identifying or recognising characteristics with a direct linkage to broadcast information or to broadcast space-time, e.g. for identifying broadcast stations or for identifying users
    • H04H60/38—Arrangements for identifying or recognising characteristics with a direct linkage to broadcast information or to broadcast space-time, e.g. for identifying broadcast stations or for identifying users for identifying broadcast time or space
    • H04H60/41—Arrangements for identifying or recognising characteristics with a direct linkage to broadcast information or to broadcast space-time, e.g. for identifying broadcast stations or for identifying users for identifying broadcast time or space for identifying broadcast space, i.e. broadcast channels, broadcast stations or broadcast areas

Definitions

  • the present invention relates to a process for analysing an analogue/digital terrestrial and/or cable television signal and to a related apparatus, especially suitable for being used by operators and technicians in order to carry out measurements with automatic signal type recognition.
  • information is transmitted through a channel having a typical frequency amplitude (also referred to as bandwidth or band amplitude) of 6, 7 or 8
  • the operator uses apparatuses which analysing the signal by scanning the frequencies typically used for television signals.
  • the operator will first scan the frequencies of the analogue television signal (if the apparatus has been previously set to the analogue television signal type) and manually note the frequencies of interest, and then he/she will carry out the same procedure for the digital terrestrial television signal and subsequently for the digital television cable signal; the signal analysis will thus take a long time, with a high probability of errors and high costs.
  • a traditional apparatus does not detect whether the signal transmission, instead of taking place within the bandwidth of the selected frequency range, occurs at 8, 7 or 6
  • the object of the present invention is to overcome the above-mentioned drawbacks. More specifically, the object of the present invention is to provide a process for analysing an analogue, digital terrestrial and/or cable television signal and a related apparatus adapted to analyse a television signal automatically without requiring the operator to set a signal type beforehand. It is a further object of the present invention to provide a process as defined above which allows to analyse the signal in a fast and accurate manner.
  • Fig. 1 is a flow chart of the process for analysing an analogue, digital terrestrial and/or cable television signal and of the related apparatus according to the invention
  • Fig. 2 is a flow chart of the process of the invention according to an embodiment which is alternative to the preferred one.
  • the process for analysing an analogue, digital terrestrial and/or cable television signal comprises a first step, represented by block 10, wherein, once the operator has selected a frequency channel on the apparatus (not shown), the signal is measured at predefined frequencies.
  • the television signal corresponding to the television channel taken into account generally has a bandwidth of approximately 8 MHz; however, the amplitude of the television channel, a priori unknown, may also be different, e.g. approx. 7 or 6 MHz.
  • the signal is preferably measured at the following frequencies:
  • ⁇ frequency of the carrier of the analogue video signal and/or within a certain neighbourhood of said frequency preferably + or - 1.25 MHz;
  • ⁇ band centre frequency of the digital channel and/or within a certain neighbourhood of said frequency preferably + or - 1.25 MHz;
  • ⁇ band centre frequency of the digital signal and/or within a certain neighbourhood of said frequency preferably + or - 1.5 MHz.
  • a selection block 12 evaluates the maximum value of the measured signal level; if said maximum value is lower than a preset value, substantially equal to 20 dB (decibel) (it should be pointed out that this value depends on the characteristics of the instrument implementing the process), then the signal will be classified as " not defined” and, for purposes which will be further explained below, the process will set the measurement instrument to the "analogue television signal" mode, as shown by block 14.
  • the signal recognition process will terminate at a block 16, or "end” block, and the apparatus will automatically set itself to the parameters for evaluating the analogue television signal, as shown by block 18, or “set analogue” block, and will consequently carry out on said signal all the measurements that will be requested by the operator on said signal.
  • the process will evaluate the difference between the maximum value and the minimum value of the measured signal level at the above- specified frequencies or frequency ranges; this evaluation will be carried out by means of a second selection block 20.
  • the television signal will be recognised as an analogue one and therefore the process will set again the conditions represented by blocks 14, 16 and 18; in fact, such a difference between the maximum value and the minimum value of the signal is a peculiarity of the analogue television signal.
  • the process will enter the condition shown by block 22, so that it will search for a digital terrestrial television signal with DVB (Digital Video Broadcasting) protocol and the TPS (Transmission Parameters Signaling) carriers of the OFDM (Orthogonal Frequency Division Multiplex) or COFDM (Coded OFDM) digital television signal, i.e. the type of television signal of digital terrestrial broadcasting; the process continues the analysis by assuming that said digital channel has the bandwidth which is typical of the frequency range in which the measurement is being carried out.
  • the TPS signal contains information about the type of digital transmission in progress, i.e. it provides indications as to which type of signal is being transmitted and with which parameters.
  • the process will then check whether the TPS signal searched for at block 22 has been "recognised” (i.e. properly synchronised and decoded) or not by the specific circuit known in the art included in the instrument and in every digital terrestrial signal receiver.
  • the process will recognise it as a digital terrestrial television signal, as shown by block 26.
  • the process will terminate at a block 28, or "end” block, and the apparatus will automatically set itself to the parameters of the digital terrestrial television signal, as shown by block 30, or "set digital" block.
  • the process according to the invention will, as shown diagrammatically by block 32, carry out one or more measurements of the signal level within a predefined frequency range.
  • said measurements are three and are carried out as follows: band centre frequency of the channel taken into consideration, from which a predefined value and substantially equal to 3.1 MHz is subtracted; however, this value may vary, depending on the application and on the instrument implementing the process, by plus/minus 2 MHz; - band centre frequency of the channel taken into consideration, from which a predefined value and substantially equal to 3.6 MHz is subtracted; however, this value may vary, depending on the application and on the instrument implementing the process, by plus/minus 2 MHz; band centre frequency of the channel taken into consideration, from which a predefined value and substantially equal to 4.1 MHz is subtracted; however, this value may vary, depending on the application and on the instrument implementing the process, by plus/minus 2 MHz.
  • This measurement allows to determine the transmission bandwidth of the digital television signal, which is generally not below 6 MHz.
  • it will check ratio between useful signal and noise, referred to as C/N ratio, at a selection block 34.
  • TPS type signals are searched for within this bandwidth and, if said signals are detected and synchronised, then the signal will be an OFDM type digital terrestrial television signal and the process will terminate in the conditions designated by blocks 26, 28 e 30.
  • the process according to the invention will carry out a verification of the amplitude of the "flatness” value (hereafter referred to as "flat") of the signal; such "flat” value is the difference between the maximum value and the minimum value of the signal oscillations.
  • the process will evaluate the "flat" value of the signal within the new bandwidth; if such value is higher than a predetermined value, preferably 6 dB, then the signal will be considered to be not defined and the apparatus implementing the process according to the invention will set itself for analysing analogue signals, as shown diagrammatically by blocks 14, 16 and 18, as described above. If, on the contrary, the flat value is lower than, for example, 6 dB, the process will go on as detailed below.
  • the process will proceed by evaluating the C/N ratio of the signal within the bandwidth determined at block 32.
  • the process according to the invention will thus evaluate the C/N ratio pertaining to the flat value of the signal, i.e. of the potential digital cable television signal. If said ratio is lower than a certain value, preferably set to 12 dB (this value however depends on the characteristics of the instrument implementing the process, so that it may vary substantially to suit the construction characteristics of the instrument itself), the process will get to the condition designated by blocks 14, 16 and 18 and will consider the signal as not defined; in such a case, the operator will carry out the analyses on the signal by taking into account the typical parameters of the analogue television signal.
  • a certain value preferably set to 12 dB
  • a C/N ratio higher than the preset value indicates the presence of a digital cable television signal; hence the process ends, as shown by a block 54 or "End” block and by a block 56 or "Set digital CATV” block, by setting the instrument to the parameters for measuring the digital cable television signal.
  • a digital cable television signal demodulator if the instrument implementing the process according to the invention incorporates a digital cable television signal demodulator, the process will carry out, following a positive output from the selection block 40, a scanning of the frequency spectrum within a neighbourhood of the tuned frequency, said neighbourhood having a predetermined width and depending on the characteristics of the instrument implementing the process, as shown schematically by a block 44, or "Spectrum analysis" block.
  • This range is statistically equal to 10 MHz if the instrument is measuring inside a defined channelling (e.g.
  • the instrument will detect the frequency value at which the signal level is maximum.
  • the process will then go on to a selection block 46, wherein it will be attempted to determine the actual bandwidth of the detected signal and the band centre frequency thereof.
  • the process will carry out continuous and repeated measurements of the signal level in a neighbourhood of the frequency at which the highest signal level has been detected.
  • the process will attempt to determine two frequencies, one within the positive neighbourhood and the other within the negative neighbourhood of the above- mentioned frequency, at which the detected signal level is lower by a preset value, preferably 3 db, than the previously detected maximum value.
  • the average value of said two frequencies will be considered by the process to be the band centre value of the signal, even though this frequency will not coincide with the frequency corresponding to the maximum level of the signal. If this search is not successful, the signal will be considered as belonging to a not defined type, and the process will continue to blocks 14, 16 and 18. The instrument will thus be set to the "analogue television signal" mode. If this search is successful, the process will consider the signal to be comprised between the two frequencies detected at selection block 46 and will then verify, at a selection block 42', that the C/N ratio within the signal band determined at block 46 is higher than a preset value and preferably equal to 12 dB.
  • the signal will be considered as belonging to a not defined type, and the process will continue to blocks 14, 16 and 18.
  • the instrument will thus be set to the analogue television signal mode.
  • the signal will have the typical characteristics of the digital cable television signal, and therefore the process will proceed to a selection block 48, wherein the Symbol Rate, i.e. the transmission bit rate of a stream of digital signals, of the detected signal will be searched for.
  • the Symbol Rate i.e. the transmission bit rate of a stream of digital signals
  • This search will be carried out by applying all possible Symbol Rates, whether standardised or allowed by ITU (International Telecommunication Union) and/or by ETSI (European Telecommunication Standard Institute) (allowed by the standardisation bodies of the specific country) to the detected signal for the specific bandwidth determined at selection block 46, and the congruence of the result will then be verified.
  • ITU International Telecommunication Union
  • ETSI European Telecommunication Standard Institute
  • the signal will be considered as belonging to a not defined type; the process will then continue with blocks 14, 16 and 18, and the instrument, as already explained above, will be set to the analogue television signal mode.
  • the process detects a Symbol Rate which is coherent with the received signal, it will attempt to recognise and detect the digital cable television signal for the detected bandwidth with the Symbol Rate determined at the previous block, as shown by a selection block 50. If the signal cannot be locked properly, then it will be considered to be a not defined cable television signal with a particular Symbol Rate (not standardised and/or not allowed by international tables), and the process will proceed to blocks 14,16 and 18.
  • a block 52 or "Digital CATV” block
  • the process will terminate with a block 54', or "End” block, and a block 56', wherein the instrument will be set to the digital cable television signal mode.
  • the advantages offered by the process according to the invention are apparent from the above description.
  • the process for analysing an analogue/digital terrestrial and/or digital cable television signal and the related apparatus according to the present invention attains and allows to perform the analysis of a television signal in a fully automatic manner; the operator is not required to set a signal type beforehand, i.e. to decide which signal type among the analogue, digital terrestrial and digital cable signals should be taken into account.
  • a further advantage provided by the process according to the invention is that it allows to carry out a signal analysis in a fast and accurate manner while at the same time avoiding the risk of any operator's errors. Also advantageously, by using the process according to the invention the operator has a more complete perception of the signal received by the user.
  • a further advantage is that the process according to the invention analyses the signal by taking into consideration different bandwidths, unlike traditional processes wherein the operator must set the amplitude of the signal band and, if the signal is not comprised within that band, nothing will be detected.

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Multimedia (AREA)
  • Databases & Information Systems (AREA)
  • Testing, Inspecting, Measuring Of Stereoscopic Televisions And Televisions (AREA)
  • Two-Way Televisions, Distribution Of Moving Picture Or The Like (AREA)
  • Circuits Of Receivers In General (AREA)

Abstract

A process for analysing an analogue/digital terrestrial and/or digital cable television signal, especially suitable for being used by operators and technicians for performing automatic signal type recognition, comprising the following steps: selecting a television channel within the specific band of the country wherein operations are carried out; measuring the signal at the frequency of the analogue video carrier within the selected frequency band; performing at least one measurement of the signal at the band centre frequency of the digital channel within the selected frequency band; - performing one or more verification tests on the signal values within the selected frequency band, suitable for determining whether the television signal is an analogue signal, a digital terrestrial signal, a digital cable signal or a not defined signal.

Description

PROCESS FOR ANALYSING AN ANALOGUE/DIGITAL TERRESTRIAL AND/OR CABLE TELEVISION SIGNAL AND RELATED APPARATUS
DESCRIPTION
The present invention relates to a process for analysing an analogue/digital terrestrial and/or cable television signal and to a related apparatus, especially suitable for being used by operators and technicians in order to carry out measurements with automatic signal type recognition. In television signal broadcasting, information is transmitted through a channel having a typical frequency amplitude (also referred to as bandwidth or band amplitude) of 6, 7 or 8
MHz; within said frequency range, it is possible to transmit the analogue television signal so as the digital terrestrial or digital cable one.
As far as the digital television signal is concerned, moreover, within the same bandwidth of the analogue channel it is also possible to transmit a plurality of signals, including data type ones.
When analysing television signals, the operator uses apparatuses which analysing the signal by scanning the frequencies typically used for television signals.
However, traditional measuring apparatuses suffer from important drawbacks, in that the operator must previously decide the type of television signal to be taken into consideration (analogue, digital terrestrial, or digital cable signal), the bandwidth thereof and set up the apparatus accordingly.
Therefore, the operator will first scan the frequencies of the analogue television signal (if the apparatus has been previously set to the analogue television signal type) and manually note the frequencies of interest, and then he/she will carry out the same procedure for the digital terrestrial television signal and subsequently for the digital television cable signal; the signal analysis will thus take a long time, with a high probability of errors and high costs.
Also, a traditional apparatus does not detect whether the signal transmission, instead of taking place within the bandwidth of the selected frequency range, occurs at 8, 7 or 6
MHz, so, in that case, no signal is detected. The operator should previously know if the transmission takes place at 6, 7 or 8 MHz, and then set up the apparatus accordingly.
The object of the present invention is to overcome the above-mentioned drawbacks. More specifically, the object of the present invention is to provide a process for analysing an analogue, digital terrestrial and/or cable television signal and a related apparatus adapted to analyse a television signal automatically without requiring the operator to set a signal type beforehand. It is a further object of the present invention to provide a process as defined above which allows to analyse the signal in a fast and accurate manner.
It is a further object of the present invention to provide a process as defined above which allows to analyse the signal in a fast and accurate manner independently of the bandwidth used for the transmission of said signal. It is a further object of the present invention to provide a process to be applied to an apparatus that can be interfaced with devices having different computing capabilities and suitable for carrying out further analyses on the television signal.
It is a further object of the present invention to provide users with a process for analysing an analogue, digital terrestrial and/or cable television signal and a related apparatus which is adapted to ensure a high level of robustness and reliability over time, and which can be manufactured easily and economically.
These and further objects are achieved by the process for analysing an analogue, digital terrestrial and/or cable television signal and a related apparatus, consisting in selecting a television channel within the specific band of the country where the analysis is being carried out, measuring the signal at the frequency of the analogue video carrier within the selected frequency band, carrying out at least one measurement of the signal at the band centre frequency of the digital channel within the selected frequency band, and making one or more verifying tests on the signal values, within the selected frequency band, suitable for determining whether the television signal is an analogue signal, a digital terrestrial signal, a digital cable signal or a not defined signal.
The construction and functional characteristics of the process for analysing an analogue, digital terrestrial and/or cable television signal and of the related apparatus according to the present invention will become apparent from the following detailed description, in which reference will be made to the annexed drawings representing a preferred but non- limiting embodiment thereof, wherein:
Fig. 1 is a flow chart of the process for analysing an analogue, digital terrestrial and/or cable television signal and of the related apparatus according to the invention; Fig. 2 is a flow chart of the process of the invention according to an embodiment which is alternative to the preferred one.
Referring now to Fig. 1, the process for analysing an analogue, digital terrestrial and/or cable television signal comprises a first step, represented by block 10, wherein, once the operator has selected a frequency channel on the apparatus (not shown), the signal is measured at predefined frequencies.
The television signal corresponding to the television channel taken into account generally has a bandwidth of approximately 8 MHz; however, the amplitude of the television channel, a priori unknown, may also be different, e.g. approx. 7 or 6 MHz. In the first phase, represented by block 10, the signal is preferably measured at the following frequencies:
■ frequency of the carrier of the analogue video signal and/or within a certain neighbourhood of said frequency, preferably + or - 1.25 MHz;
■ band centre frequency of the digital channel and/or within a certain neighbourhood of said frequency, preferably + or - 1.25 MHz;
■ band centre frequency of the digital signal and/or within a certain neighbourhood of said frequency, preferably + or - 1.5 MHz.
By carrying out the measurements at said frequencies, the instrument can find and store the maximum and minimum values of the signal level at each measurement point. A selection block 12 evaluates the maximum value of the measured signal level; if said maximum value is lower than a preset value, substantially equal to 20 dB (decibel) (it should be pointed out that this value depends on the characteristics of the instrument implementing the process), then the signal will be classified as " not defined" and, for purposes which will be further explained below, the process will set the measurement instrument to the "analogue television signal" mode, as shown by block 14.
In such a case, the signal recognition process will terminate at a block 16, or "end" block, and the apparatus will automatically set itself to the parameters for evaluating the analogue television signal, as shown by block 18, or "set analogue" block, and will consequently carry out on said signal all the measurements that will be requested by the operator on said signal.
In particular, should the level of the signal received by the instrument be lower than the sensitivity threshold of the latter, the process according to the invention will -A-
automatically set the operating condition associated with the analogue television signal, as defined by the above-mentioned blocks 14, 16 and 18, and will allow the instrument to properly detect the absence of any signal or a null signal (when the signal level is lower than the sensitivity threshold of the instrument itself). If the measured signal level, evaluated at selection block 12, is higher than the value preset substantially to 20 dB, then the process will evaluate the difference between the maximum value and the minimum value of the measured signal level at the above- specified frequencies or frequency ranges; this evaluation will be carried out by means of a second selection block 20. If the difference between the maximum value and the minimum value is greater than a preset value, preferably equal to 20 dB, the television signal will be recognised as an analogue one and therefore the process will set again the conditions represented by blocks 14, 16 and 18; in fact, such a difference between the maximum value and the minimum value of the signal is a peculiarity of the analogue television signal. In case the difference between the maximum value and the minimum value of the measured signal level is smaller than 20 dB, the process will enter the condition shown by block 22, so that it will search for a digital terrestrial television signal with DVB (Digital Video Broadcasting) protocol and the TPS (Transmission Parameters Signaling) carriers of the OFDM (Orthogonal Frequency Division Multiplex) or COFDM (Coded OFDM) digital television signal, i.e. the type of television signal of digital terrestrial broadcasting; the process continues the analysis by assuming that said digital channel has the bandwidth which is typical of the frequency range in which the measurement is being carried out. The TPS signal contains information about the type of digital transmission in progress, i.e. it provides indications as to which type of signal is being transmitted and with which parameters.
Through a third selection block 24, the process will then check whether the TPS signal searched for at block 22 has been "recognised" (i.e. properly synchronised and decoded) or not by the specific circuit known in the art included in the instrument and in every digital terrestrial signal receiver.
If said signal has been decoded, then the process will recognise it as a digital terrestrial television signal, as shown by block 26. In such a case, as already described for the analogue television signal, the process will terminate at a block 28, or "end" block, and the apparatus will automatically set itself to the parameters of the digital terrestrial television signal, as shown by block 30, or "set digital" block. In the event that the TPS signal is not properly recognised, e.g. due to a signal bandwidth different from the typical one of the frequency range taken into account (for example, a bandwidth of 6 MHz), the process according to the invention will, as shown diagrammatically by block 32, carry out one or more measurements of the signal level within a predefined frequency range. In the preferred embodiment, said measurements are three and are carried out as follows: band centre frequency of the channel taken into consideration, from which a predefined value and substantially equal to 3.1 MHz is subtracted; however, this value may vary, depending on the application and on the instrument implementing the process, by plus/minus 2 MHz; - band centre frequency of the channel taken into consideration, from which a predefined value and substantially equal to 3.6 MHz is subtracted; however, this value may vary, depending on the application and on the instrument implementing the process, by plus/minus 2 MHz; band centre frequency of the channel taken into consideration, from which a predefined value and substantially equal to 4.1 MHz is subtracted; however, this value may vary, depending on the application and on the instrument implementing the process, by plus/minus 2 MHz.
This measurement allows to determine the transmission bandwidth of the digital television signal, which is generally not below 6 MHz. When the process has determined the signal bandwidth, it will check ratio between useful signal and noise, referred to as C/N ratio, at a selection block 34.
If said C/N ratio turns out to be lower than a predefined value, preferably 4 dB, then the signal will be recognised by the apparatus as not belonging to the digital terrestrial type. The process will then proceed to a block 40 which will be described later on. If, on the contrary, the C/N ratio is higher than 4 dB, the process will go on to a block 36, or "band" block; in this condition, the apparatus implementing the process according to the invention will carry out the steps described below within the bandwidth detected at block 32.
As shown by a selection block 38, TPS type signals are searched for within this bandwidth and, if said signals are detected and synchronised, then the signal will be an OFDM type digital terrestrial television signal and the process will terminate in the conditions designated by blocks 26, 28 e 30.
In case no TPS signals are locked and properly decoded within the new bandwidth, the process according to the invention will carry out a verification of the amplitude of the "flatness" value (hereafter referred to as "flat") of the signal; such "flat" value is the difference between the maximum value and the minimum value of the signal oscillations. As schematised by a selection block 40, the process will evaluate the "flat" value of the signal within the new bandwidth; if such value is higher than a predetermined value, preferably 6 dB, then the signal will be considered to be not defined and the apparatus implementing the process according to the invention will set itself for analysing analogue signals, as shown diagrammatically by blocks 14, 16 and 18, as described above. If, on the contrary, the flat value is lower than, for example, 6 dB, the process will go on as detailed below.
If the instrument implementing the process according to the invention does not incorporate a digital cable television signal demodulator, or if it incorporates one but the operator wants the process to be completed more quickly, the process will proceed by evaluating the C/N ratio of the signal within the bandwidth determined at block 32.
Through a selection block 42, the process according to the invention will thus evaluate the C/N ratio pertaining to the flat value of the signal, i.e. of the potential digital cable television signal. If said ratio is lower than a certain value, preferably set to 12 dB (this value however depends on the characteristics of the instrument implementing the process, so that it may vary substantially to suit the construction characteristics of the instrument itself), the process will get to the condition designated by blocks 14, 16 and 18 and will consider the signal as not defined; in such a case, the operator will carry out the analyses on the signal by taking into account the typical parameters of the analogue television signal. A C/N ratio higher than the preset value (which has been assumed to be 12 dB in this example, but, as mentioned above, it may vary considerably) indicates the presence of a digital cable television signal; hence the process ends, as shown by a block 54 or "End" block and by a block 56 or "Set digital CATV" block, by setting the instrument to the parameters for measuring the digital cable television signal.
Referring now to Fig. 2, wherein common blocks of the process are designated by the same reference numerals, if the instrument implementing the process according to the invention incorporates a digital cable television signal demodulator, the process will carry out, following a positive output from the selection block 40, a scanning of the frequency spectrum within a neighbourhood of the tuned frequency, said neighbourhood having a predetermined width and depending on the characteristics of the instrument implementing the process, as shown schematically by a block 44, or "Spectrum analysis" block. This range is statistically equal to 10 MHz if the instrument is measuring inside a defined channelling (e.g. inside a channelling reproducing the official channelling of a country where the verification is being carried out), or is statistically equal to 20 MHz if the instrument is verifying and analysing a signal outside a predefined channelling. This allows to reduce the search time when it is not necessary to scan a wider range, as well as to minimise the number of false or negative signals when the spectrum is explored freely. During the scanning performed at block 44, the instrument will detect the frequency value at which the signal level is maximum.
The process will then go on to a selection block 46, wherein it will be attempted to determine the actual bandwidth of the detected signal and the band centre frequency thereof. To this end, the process will carry out continuous and repeated measurements of the signal level in a neighbourhood of the frequency at which the highest signal level has been detected. The process will attempt to determine two frequencies, one within the positive neighbourhood and the other within the negative neighbourhood of the above- mentioned frequency, at which the detected signal level is lower by a preset value, preferably 3 db, than the previously detected maximum value.
The average value of said two frequencies will be considered by the process to be the band centre value of the signal, even though this frequency will not coincide with the frequency corresponding to the maximum level of the signal. If this search is not successful, the signal will be considered as belonging to a not defined type, and the process will continue to blocks 14, 16 and 18. The instrument will thus be set to the "analogue television signal" mode. If this search is successful, the process will consider the signal to be comprised between the two frequencies detected at selection block 46 and will then verify, at a selection block 42', that the C/N ratio within the signal band determined at block 46 is higher than a preset value and preferably equal to 12 dB.
If the verification fails, the signal will be considered as belonging to a not defined type, and the process will continue to blocks 14, 16 and 18. The instrument will thus be set to the analogue television signal mode.
If the search carried out at selection block 42' is successful, the signal will have the typical characteristics of the digital cable television signal, and therefore the process will proceed to a selection block 48, wherein the Symbol Rate, i.e. the transmission bit rate of a stream of digital signals, of the detected signal will be searched for.
This search will be carried out by applying all possible Symbol Rates, whether standardised or allowed by ITU (International Telecommunication Union) and/or by ETSI (European Telecommunication Standard Institute) (allowed by the standardisation bodies of the specific country) to the detected signal for the specific bandwidth determined at selection block 46, and the congruence of the result will then be verified. In the event that none of these Symbol Rate values produces a congruent result, the signal will be considered as belonging to a not defined type; the process will then continue with blocks 14, 16 and 18, and the instrument, as already explained above, will be set to the analogue television signal mode. If the process detects a Symbol Rate which is coherent with the received signal, it will attempt to recognise and detect the digital cable television signal for the detected bandwidth with the Symbol Rate determined at the previous block, as shown by a selection block 50. If the signal cannot be locked properly, then it will be considered to be a not defined cable television signal with a particular Symbol Rate (not standardised and/or not allowed by international tables), and the process will proceed to blocks 14,16 and 18.
If, on the contrary, the signal is locked properly, then it will be considered, as shown by a block 52, or "Digital CATV" block, to be a digital cable signal and the process will terminate with a block 54', or "End" block, and a block 56', wherein the instrument will be set to the digital cable television signal mode.
The advantages offered by the process according to the invention are apparent from the above description. The process for analysing an analogue/digital terrestrial and/or digital cable television signal and the related apparatus according to the present invention attains and allows to perform the analysis of a television signal in a fully automatic manner; the operator is not required to set a signal type beforehand, i.e. to decide which signal type among the analogue, digital terrestrial and digital cable signals should be taken into account.
A further advantage provided by the process according to the invention is that it allows to carry out a signal analysis in a fast and accurate manner while at the same time avoiding the risk of any operator's errors. Also advantageously, by using the process according to the invention the operator has a more complete perception of the signal received by the user.
A further advantage is that the process according to the invention analyses the signal by taking into consideration different bandwidths, unlike traditional processes wherein the operator must set the amplitude of the signal band and, if the signal is not comprised within that band, nothing will be detected. Although the invention has been disclosed herein with reference to an explanatory, non- limiting embodiment thereof, many changes and variations may still be made to it by those skilled in the art in the light of the above description. Therefore, the present invention is meant to embrace any changes or variations falling within the spirit and scope of the appended claims.

Claims

1. Process for analysing an analogue/digital terrestrial and/or digital cable television signal, especially suitable for being used by operators and technicians for performing automatic signal type recognition, consisting of:
- selecting a television channel within the specific band of the country wherein operations are carried out;
- measuring the signal at the frequency of the analogue video carrier within the selected frequency band;
- performing at least one measurement of the signal at the band centre frequency of the digital channel within the selected frequency band; - performing one or more verification tests on the signal values, within the selected frequency band, suitable for determining whether the television signal is an analogue signal, a digital terrestrial signal, a digital cable signal or a not defined signal.
2. Process according to claim 1, wherein the maximum value and the minimum value of the measured signal level are stored.
3. Process according to claim 1, wherein the measurement of the signal is carried out within a neighbourhood of + or - 1.25 MHz of the band centre frequency of the carrier of the analogue video channel.
4. Process according to claim 1, wherein the measurement of the signal is carried out within a neighbourhood of + or - 1.5 MHz of the band centre frequency of the digital channel.
5. Process according to one or more of the preceding claims, wherein within a selection block (12) the maximum frequency value of the measured signal is compared with a known value substantially equal to 20 dB.
6. Process according to one or more of the preceding claims, wherein within a selection block (20) the difference between the maximum value and the minimum value of the measured signal is compared with a known value substantially equal to 20 dB.
7. Process according to one or more of the preceding claims, wherein a search is carried out within a block (22) for a signal with TPS (Transmission Parameters Signaling) protocol of the OFDM (Orthogonal Frequency Division Multiplex) or COFDM (Coded OFDM) digital channel.
8. Process according to one or more of the preceding claims, wherein a test is carried out within a selection block (24) which test is suitable for verifying if the signal with TPS protocol has been detected and properly decoded.
9. Process according to one or more of the preceding claims, wherein one or more signal level measurements are carried out within a block (32) at certain frequencies or frequency ranges within the channel taken into account.
10. Process according to claim 9, wherein the signal level measurement is carried out by subtracting 3.1 MHz from the band centre frequency of the channel taken into account.
11. Process according to claim 10, wherein the signal level measurement is carried out by subtracting 3.1 MHz + or - 2 MHz from the band centre frequency of the channel taken into account.
12. Process according to claim 9, wherein the signal level measurement is carried out by subtracting 3.6 MHz from the band centre frequency of the channel taken into account.
13. Process according to claim 12, wherein the signal level measurement is carried out by subtracting 3.6 MHz + or - 2 MHz from the band centre frequency of the channel taken into account.
14. Process according to claim 9, wherein the signal level measurement is carried out by subtracting 4.1 MHz from the band centre frequency of the channel taken into account.
15. Process according to claim 14, wherein the signal level measurement is carried out by subtracting 4.1 MHz + o - 2 MHz from the band centre frequency of the channel taken into account.
16. Process according to claim 9, wherein at a selection block (34) the carrier-to-noise ratio, or C/N ratio, is compared with a known value preferably equal to 4 dB.
17. Process according to claim 9, wherein at a selection block (40) the amplitude of the "flat" value of the signal is compared with a known value preferably equal to 6 dB.
18. Process according to claim 17, wherein at a selection block (42) the C/N ratio is compared with a known value preferably equal to 12 dB.
19. Process according to claim 9, wherein within a selection block (38) TPS type signals are searched for, detected and decoded.
20. Process according to claim 17, wherein within a "Spectrum analysis" block (44) a scanning is performed on the frequency spectrum within a certain neighbourhood of the tuned frequency band.
21. Process according to claim 20, wherein within a selection block (46) the actual bandwidth of the detected signal and the band centre frequency thereof are determined.
22. Process according to claim 21, wherein within a selection block (42') the C/N ratio of the band centre frequency of the signal is compared with a known value preferably equal to 12 dB.
23. Process according to claim 22, wherein within a selection block (48) it is repeatedly attempted to "lock" and decode the signal by taking into consideration in succession all possible Symbol Rate values standardized and/or allowed by ITU
(International Telecommunication Union) and/or by ETSI (European
Telecommunication Standard Institute) (allowed by the standardization bodies of the specific country) for the specific bandwidth determined at selection block 46, and by verifying that the result is congruent with the received signal.
24. Process according to claim 23, wherein within a selection block (50) it is attempted to detect, recognise, "lock" and decode the digital cable television signal, by taking into account the previously detected bandwidth and the Symbol Rate determined to be congruent at the previous selection block (48).
25. Apparatus according to one or more of the preceding claims for implementing the process for analysing an analogue/digital terrestrial television signal, and digital cable television signal.
PCT/IB2008/001983 2007-07-31 2008-07-30 Process for analysing an analogue/digital terrestrial and/or cable television signal and related apparatus WO2009016475A2 (en)

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ITMI20071565 ITMI20071565A1 (en) 2007-07-31 2007-07-31 PROCESS FOR THE ANALYSIS OF AN ANALOGUE AND DIGITAL TV SIGNAL AND ITS APPARATUS

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