EP2328288A1 - System and method for detecting and localising impedance error adjustments - Google Patents

Abstract

The system has a power detector (302) for informing a microprocessor-controller (308) that high-frequency signals are present at an input. A local oscillator (305) and a mixer (303) are provided for converting the signals into intermediate frequency, where the system is designed in such a manner that the signals are input signals in a satellite master antenna TV-network. The microprocessor-controller detects the position of impedance-error adjustments in the network. A user interface (309) is provided for communicating a user with the microprocessor-controller. An independent claim is also included for a method for detecting and localizing impedance error adjustments in a satellite master antenna TV-network.

Description

The present invention relates to a system and method for detecting and locating impedance mismatches, particularly in SMATV networks.

The invention relates to the field of reflectometry in the frequency domain, specifically the field of detection and localization of impedance mismatches within SMATV networks (SMATV = satellite master antenna television), where only signals from these networks are used without any other signal through the inventive system is inserted.

State of the art

The distribution networks for TDT services and satellite television systems, depending on their design, contain a variety of impedance mismatching on the links on which radio frequency signals are transmitted from the head unit to the user socket. The reflected waves appear essentially in all those discontinuities that exist in SMATV networks, that is, in connections between distributors, dissipators, sockets, and in coaxial cables, due to the fact that the devices used in the network are not ideal. This can lead to low detection time echoes located in key points of the network; and there may also be another set of mismatches caused by defective or disconnected cables, the poor condition of the distribution elements, and also difficulty in identifying installation errors.

The effect of an impedance mismatch at a particular location of an SMATV network is that a reflection or echo of the signal at that point is generated with different amplitude and phase. Reflections can affect the signal distribution in the rest of the network in constructive or destructive form due to the aforementioned change in amplitude and phase in the reflected signal. Therefore, a network that is inappropriately treated may show undesirable effects. As a result of these reflections, the signal may be significantly degraded in performance, so some of the services may not be provided to some users.

This is true in the case of digital terrestrial transmission signals, especially in the case of satellite signals, where the existence of error protection techniques due to inter-symbol interference (ISI) is very limited.

Another critical case is when data is sent over coaxial cable, again because multipath phenomena lead to interference between symbols. Although the actual design of these networks can usually mitigate the consequences of the existence of rebound of the signal in the rest of the network, the stage in which the network is installed is necessary for the correct reception of the signal in these networks in order to detect all the delayed signals. which are or are not provided for in the stage of development or set-up triggered by the uncontrolled, previously annotated motives.

Today, the solutions available in the field of impedance mismatch detection provide that the position of these disturbances is obtained by inserting a known signal and by later receiving (intercepting) the signal caused by the isolation of the impedances. Logically, when using these devices, one works in SMATV networks, where no other signal is inserted which is not a signal of the actual device. There are several scenarios where this happens. The first situation is the one where the network is still in the installation phase. In this case, no signal is transmitted to any of the possible users of the network, so that there is no possibility to interfere with the needs of the user. In the second case, a network is fully functional, but to identify the reflections it is necessary to separate the head unit signal so as not to interfere with the measurement process. Of course, this is an undesirable situation because it requires terminating services for different users connected to the SMATV network.

Currently, there is no technique to capture the source of impedance mismatches in the network without taking the user's services. Therefore, when searching for the position of the clutter or echo within an SMATV network, it becomes necessary to discontinue the propagation of the signal, thereby interrupting the reception of contents in each of the distribution sockets, with the corresponding drawback for the group of Users who want to use the services offered.

As already stated, the current focus for the determination of the presence of mismatches in the adaptation of impedances is essentially based on the insertion of a known signal into the network and on the later reception (interception) of the reflections resulting in decoupling of the network (reflectometry). have their origin. Depending on the type of domain being worked on, that is, time or frequencies, there are two possible ways to solve the problem. Time domain reflectometry (TDR) is the transmission of a pulse to the device to be evaluated and the interception of the reflected signal in the device. This technique is often used to study the parameters of the lossy transmission lines, such as in the American patent US 006437578B1 labeled, "Distance to Fault Cable Loss Correction and Time Domain Reflectometer Measurements." The sampling rates for capturing the signal in the field of reflectometry in the time domain require the use of too high a clock, which increases the complexity of the recognition tools. Due to limitations of the TDR system to verify the existence of errors in function of the frequency in the system to be analyzed, there is a very different approach. This is known reflectometry, which works in the frequency domain (FDR). This is a very commonly used strategy in measuring instruments due to the need for a lower sampling rate (hence less complex) and the increased measure of observing the spectral variation of the process parameters. This technique produces spectral noise, usually with one tone or a series of tones, so that the effects of impedance mismatches versus frequency are obtained by the reflection of these sinusoids. Examples of the use of this technique are the US patents US 006868357B2 entitled "Frequency Domain Reflectometry for Testing and Cable Use in Situ Connectors, Passive Conectivity, Cable Fray Detection, and Live Wire Testing" and US 006691051 B2 entitled "Transient distance to fault measurement".

In the known frequency range of reflectometry, there are several variants. So there is the phase detection FDR (PDFDR), which produces the phase difference between the waves, the standing wave reflectometry (SWR), which measures the size of the standing wave by the superposition of the incident and reflected waves, the size of the Waves, the frequency-modulated continuous wave (FMCW), which uses one of a set of sinusoids whose frequency is linearly increased, and the mixed-signal reflectometry (MSR) as in the US patent US007215126B2 presented with the title "Apparatus and method for testing a signal path from an injection point "and in" Mixed Signal Reflectometer for Location o Faults on Aging Wiring "," Peijung Tsai et al, IEEE Sensors Journal, vol. 5, No. 6 December 2005 , a technique that uses the sum of two sine waves, one incident and one reflected, and which extracts the DC component, which is the result of obtaining the square of that operation.

In addition to the described tools, there are other possibilities for detecting signal reflections for the common use of reflectometry in time and frequency. This third way is called Time-Frequency Domain Reflectometry (TFDR), see the European patent EP 1477820 A2 entitled "Wire fault detection" or the publication IEEE Transactions on Instrumentation and Measurement, Vol. 54, No. 6, December 2005 entitled "Application of time-frequency domain reflectormety for detection on localization of a fault on a coxial cable" by Yong-Jun Shin, and Edward J. Powers, with examples of their use.

The common point of all the technologies described so far is the application of a signal generated internally to make the measurements, and occasionally the use of other devices to correctly carry out the proposed measures. The insertion of the network signal and the interception of the reflections must be performed at the same physical point, with hardware complexity necessary to use a device to separate the reflected signal from the transmitted signal. This approach is not arbitrary, because if the signal is generated elsewhere in the network, unlike the place where the reflection is intercepted, it is desirable not just the various components of the detection, the transmitter and the receiver It is also essential to analyze the network to the last detail in order to be able to predict, from both signals, the effect and the position of the delayed components of the main signal. The fact of inserting a known signal in the network and detecting the reflection in the same place directly places demands on the hardware design of the device in question and considerably increases its complexity. Moreover, locating the origin of the reflected waves requires sampling the signal at a rate high enough to distinguish very close echoes. The greater the spatial accuracy desired, the higher the sampling rate. Moreover, another of the many shortcomings of the current mismatch detectors has been found to be that it is necessary for the device to input a known signal into the network, and it is appropriate to do so temporarily suspend providing services, which is without a doubt a disadvantage for the user.

Finally, if the technical staff responsible for carrying out these tasks wishes to limit the search for delays to a particular area of the SMATV network, then physical shutdown of the corresponding network components must be done, thus rendering the services that provide the services Users of these networks are received, restricted.

DESCRIPTION

It is an object of the present invention to provide a system for detecting and locating impedance mismatches in SMATV networks and a method for quantifying the length of coaxial cables present in these networks.

This object is achieved by a system and a method as defined in the claims. In this case, the spectral shape of the channels transmitted in an SMATV network is used to obtain information about the impedance mismatches in this system, in particular as defined in the claims.

The present invention has a variety of advantages.

An advantageous embodiment of the invention is formed by a system for detecting and locating impedance mismatches in SMATV networks. This includes a radio frequency input, a means for detecting energy, a mixer for converting a given signal to an intermediate frequency, a band-pass filter, an analog-to-digital converter, and an automatic gain control circuit. This system is characterized in that it is designed in such a way that input signals in an SMATV network are signals which are not input by the system. System intrinsic signals are used to detect and locate impedance mismatches.

This provides the advantage of not having to input a signal into the SMATV network, which is also associated with the further advantage of lower complexity and lower cost of the system.

A further advantageous embodiment of the invention is characterized in that the system is designed in such a way that the input signals are the system-internal signals in the SMATV network signals which lie in the frequency range in which signals be distributed in the network. This provides the advantage that those signals transmitted in the respective band can be used, which are characterized by the absence of "multipath" problems in the signal, thus eliminating the possible presence of false positives.

A further embodiment of the invention is characterized in that the system is designed in such a way that the resolution of the room recognition, the bandwidth used and the rank of the room recognition are varied. This provides the advantage of improving the accuracy of the measurement and detection of very close impedance mismatches, and limits the length of the path traveled by the reflections to a particular value.

A further advantageous embodiment of the invention is characterized in that the system is designed in such a way that the length of a given coaxial cable within a SMATV network is measured. In this way, the topology of the network can advantageously be determined by the measurement at different network points.

A further advantageous embodiment of the invention is characterized in that the system is designed in such a way that the distance to the failure of coaxial cables in SMATV networks is measured. This provides the advantage that the correct operation of the coaxial cable can be detected in SMATV networks whose topology is known.

A further advantageous embodiment of the invention is characterized in that the system is designed in such a way that the results, which were determined in different measurements at various points of the SMATV network, are compared with one another. This provides the advantage that the source of the various impedance mismatches can be distinguished in the case of ambiguous situations.

A further advantageous embodiment of the invention is characterized in that the difference of the corresponding spectra from different measurements at different points of the SMATV network are used as input signal. This provides the advantage of eliminating the effects of false positives derived from a possible periodicity in the form of the spectrum of the signal which is used in detection, thus maximizing the effects of mismatches.

In the following, the advantages and the characteristics of the invention will be explained with reference to the following description in which reference is made to the attached figures.

In der vorgenannten Gleichung entspricht X_rec (ω) der Fouriertransformation des an einem konkreten Punkt eines SMATV-Netzes empfangenen Signals, in dem K Impedanz-Fehlanpassungen bestehen. X(ω) ist die Fouriertransformierte des Signals, das dem SMATV-Netz übergeben wird, ohne dass eine Modifikation durch die Wirkung der Fehlanpassungen vorliegt (X(ω) ist die Hilbert-Transformierte),

y

sind die Real- bzw. Imaginärteile eines jeden der K Reflexionskoeffizienten, die den verschiedenen Impedanz-Fehlanpassungen im SMATV-Netz zugeordnet sind und ^τk ist die Verzögerung einer jeden Replik, die durch dieses Fehlanpassungen bezüglich des direkten Signals X(ω) gebildet ist. FIG. 1 Figure 12 is a block diagram showing details of the system and method for detecting and locating impedance mismatches. At point 101, the spectrum of the signal used to detect and locate the location of the mismatches is obtained. The acquired spectrum contains information about the presence of impedance mismatches in the network according to the following equation: $$X_{\mathit{rec}}\left(\omega \right)=X\left(\omega \right)+{\displaystyle \underset{k=1}{\overset{K}{\Sigma }}}\left\{{\rho }_{R_k}X\left(\omega \right)+{\rho }_{I_k}\hat{X}\left(\omega \right)\right\}{e}^{{\mathit{j\omega \tau }}_k}$$

In the above equation, X _rec ( ω ) corresponds to the Fourier transform of the signal received at a specific point of an SMATV network in which K impedance mismatches exist. X ( ω ) is the Fourier transform of the signal passed to the SMATV network without modification due to the effect of the mismatches ( X ( ω ) is the Hilbert transform),

y

are the real and imaginary parts of each of the K reflection coefficients associated with the different impedance mismatches in the SMATV network, and ^τ k is the delay of each replica formed by this mismatching with the direct signal X ( ω ).

mit $${\left|X\left(\omega \right)\right|}^2={\left|1+{\displaystyle \sum _{k=1}^K}\left\{{\rho }_{R_k}+{\rho }_{I_k}{e}^{-j\frac{\pi }{2}}\right\}{e}^{{\mathit{j\omega \tau }}_k}\right|}^2$$

The maximum bandwidth of the signal used is limited to the corresponding rank of propagation or signals within an SMATV network, whereby it is possible to use a lower bandwidth. The bandwidth used is directly related to the time resolution used in the detection of the reflections according to the equation Tc = 1 / B, where Tc is the period of time sampling and B is the bandwidth of the signal used. Thus, the spatial resolution of the present invention and the time resolution have a proportional relationship, derived from the equation D = vp * Tc, where D is the spatial resolution and vp is the velocity of the characteristic propagation of the coaxial cable. After the spectrum of the signal is obtained, one obtains the modulus of this spectrum in block 102. After the spectrum of the selected signal is obtained, in block 103 a reduction of the noise that is present in the spectrum. The resulting signal is subject to spectral transformations in block 104, where the signal modulus is taken by a factor of n in block 1041, where n = 2 represents only a non-limiting example of a factor to be selected. This results at the output of this block $${\left|X_{\mathit{rec}}\left(\omega \right)\right|}^2={\left|X\left(\omega \right)\right|}^2{\left|H\left(\omega \right)\right|}^2$$

With $${\left|X\left(\omega \right)\right|}^2={\left|1+{\displaystyle \underset{k=1}{\overset{K}{\Sigma }}}\left\{{\rho }_{R_k}+{\rho }_{I_k}{e}^{-j\frac{\pi }{2}}\right\}{e}^{{\mathit{j\omega \tau }}_k}\right|}^2$$

wobei A_k und B_k Konstanten sind, die den Einfluss eines jeden Koeffizienten der Impedanz-Fehlanpassungen umfassen, die in dem SMATV-Netz vorhanden sind hinsichtlich einer jeden Verzögerung ^τk , die durch eine konkrete Fehlanpassung gebildet ist. Auf diese Weise ergibt sich, dass die Wirkung der Fehlanpassungen auf das Spektrum des in dem SMATV-Netzes übertragenen Signals sich umsetzt in deren Multiplikation durch die Summe einer Reihe von Signalen, die aus Sinusoiden abgeleitet sind.In the latter equation, when the square of the modulus is developed, the following equation results: $$\begin{array}{ll}{\left|H\left(\omega \right)\right|}^2& =1+{\displaystyle \underset{k=1}{\overset{K}{\Sigma }}}{A}_k\cos \left({\mathrm{\omega \tau }}_k\right)\\ & +2{\displaystyle \underset{k=1}{\overset{K-1}{\Sigma }}}{\displaystyle \underset{r=k}{\overset{K}{\Sigma }}}{B}_k\cos \left(\omega \left|{\tau }_k-{\tau }_r\right|\right)\\ & +{\displaystyle \underset{k=1}{\overset{K}{\Sigma }}}{\left|{\alpha }_k\right|}^2\end{array}$$

where A _k and B _{k are} constants that include the influence of each coefficient of impedance mismatches present in the SMATV network with respect to each delay ^τ k formed by a concrete mismatch. In this way it follows that the effect of the mismatches on the spectrum of the signal transmitted in the SMATV network translates into their multiplication by the sum of a series of signals derived from sineoids.

After the signal is formed at the output of block 1041, it serves as an input signal to the block 1042 in which a transformation of the spectrum is made which makes it possible to better decouple the signal transmitted over the SMATV network from the effects of the network. A non-limiting example is the application of a logarithmic function, a base 10 logarithm, which allows the effect of the mismatch to be separated on the transmitted signal.

wobei $$\begin{array}{cc}10{\log }_{10}\left(\begin{array}{c}{\left|H\left(\omega \right)\right|}^2\end{array}\right)& =10{\log }_{10}\left(1+2{\displaystyle \sum _{k=1}^K}{A}_k\cos \left({\mathrm{\omega \tau }}_k\right)\right)\end{array}+2{\displaystyle \sum _{k=1}^{K-1}}{\displaystyle \sum _{r=k}^K}{B}_k\cos \left(\omega \left|{\tau }_k-{\tau }_r\right|\right)+{\displaystyle \sum _{k=1}^K}{\left|{\alpha }_k\right|}^2)$$

Applying this transformation to the previous equations yields the following equation $$\begin{array}{ll}10{\log }_{10}{\left|X_{\mathit{rec}}\left(\omega \right)\right|}^2& =10{\log }_{10}\left({\left|X\left(\omega \right)\right|}^2{\left|H\left(\omega \right)\right|}^2\right)\\ & =10{\log }_{10}\left({\left|X\left(\omega \right)\right|}^2\right)+10{\log }_{10}\left({\left|H\left(\omega \right)\right|}^2\right)\end{array}$$

in which $$\begin{array}{cc}10{\log }_{10}\left(\begin{array}{c}{\left|H\left(\omega \right)\right|}^2\end{array}\right)& =10{\log }_{10}\left(1+2{\displaystyle \underset{k=1}{\overset{K}{\Sigma }}}{A}_k\cos \left({\mathrm{\omega \tau }}_k\right)\right)\end{array}+2{\displaystyle \underset{k=1}{\overset{K-1}{\Sigma }}}{\displaystyle \underset{r=k}{\overset{K}{\Sigma }}}{B}_k\cos \left(\omega \left|{\tau }_k-{\tau }_r\right|\right)+{\displaystyle \underset{k=1}{\overset{K}{\Sigma }}}{\left|{\alpha }_k\right|}^2)$$

und die entsprechende Beziehung mit dem Logarithmus auf Basis 10 $${\log }_{10}\left(x\right)=\frac{\ln \left(x\right)}{\ln \left(10\right)},$$

impliziert das Ergebnis, den Logarithmus auf das Signal |X_rec (ω)|² anzuwenden, die Umwandlung des Produkts |X(ω)|² y |H(ω)|² in eine Summe zu der Zeit, die diese letzte Funktion fortführt, wobei diese gebildet wird durch eine Kombination der Signale, die aus Sinussoiden abgeleitet ist.Considering the Taylor approximation of the Neperiano logarithm function $$\ln \left(1+x\right)={\displaystyle \underset{n=1}{\overset{\infty }{\Sigma }}}\frac{{\left(-1\right)}^{n+1}}{n}{x}^n$$

and the corresponding relationship with the logarithm based on 10 $${\log }_{10}\left(x\right)=\frac{\ln \left(x\right)}{\ln \left(10\right)}.$$

implies the result, the logarithm on the signal | X _rec (ω) | ² , the conversion of the product | X ( ω ) | ² y | H ( ω ) | ² into a sum at the time this last function continues, this being formed by a combination of the signals derived from sinusoids.

After these transformations have been applied, the inverse Fourier transform (IFT) of N points (block 105) is formed. The number N limits the rank of detectable mismatches to N * D / 2 since the application of IIFT is applied to a true signal and one obtains a complex symmetric signal so that one half of the points can be excluded.

As a result of this block, one applies a process of the time response 106, which consists of obtaining the module 1061 of the resulting complex signal and the subsequent collection to a known power 1062. The result is converted into a A plurality of maxima whose time position corresponds to each of the delays ^τ k corresponding to each impedance mismatch in the SMATV network.

After the results of the aforementioned blocks have been formed, a normalization 107 is formed which allows a comparison between different measurements made throughout the SMATV network.

The resulting signal is similar to the signal in FIG. 4 where, because of the periodicity of the input spectrum, as shown FIG. 8 It can be seen that false positives can occur that can easily be confused with actual impedance mismatches. These false positives can be easily recognized by calculating the periodicity of the input spectrum and they can be removed by comparing the spectra formed at different points of the SMATV network and using the difference as input to the system according to the invention, whereby results are achieved in FIG. 5 are shown.

The process of detection and localization of the impedance mismatches ends with the detection of the maxima in the signal 108 and with the extraction of the special position associated with the time delay of the different maxima of the signal.

Figur 1

Erkennung von Impedanz-Fehlanpassungen

101, OE

Bildung (Gewinnung) des Spektrums

102

Block der Bildung des Spektrummoduls

103

Geräuschreduktion.

104

Transformation des Spektrums

105

Inverse Fourier-Transformation von N Punkten

106

Bearbeitung der Zeitantwort

107

Normierung.

108, DM

Erkennung von Maximalwerten

Figur 2

Spektraltransformationsblock

1041

Block der Quadratbildung

1042

Block der Transformation des Spektrums

Figur 3

Block der Bearbeitung der Zeitantwort

1061

Block der Bildung des Spektrummoduls

1062

Block der Quadratbildung

Figur 4

Komponenten, die sich aus der Form des Eingangssignals ergeben

Figur 5

Erkennung der Position der Impedanzfehlanpassungen.

Figur 6

SMATV-Netz, in dem TV-Signale oder ein anderes bekanntes Signal gemessen wird

201

Satellitensignalantenne

202

Mischer

203

Ableitungskomponenten

204

Verteilungsnetz

205

Benutzungssteckdosen

206

Lokalisierungseinrichtung

207

Koaxialkabel

Figur 7

Ausführungsbeispiel der Erfindung

301

Eingangsanschluss des Signals

302

Einrichtung zur Energie-Erkennung

303

Mischer

304

Bandpassfilter

305

Lokaloszillator für Zwischenfrequenzsignal

306

Automatische Verstärkungsregelungsschaltung (AGC)

307

Analog-Digital-Wandler (A / D)

308

Mikroprozessor-Steuerung

309

Schnittstelle mit Benutzer

310

Optisches Endgerät

311

FPGA

Figur 8

Sätze von Satellitenprogrammen im ZF-Band FI

Figur 9

Weiteres Ausführungsbeispiel der Erfindung

401

Satelliten-Signal Antenne

402

Mixer

403

Ausschnitt aus einem Verteilnetz unbekannter Netztopologie

404

Ableitungselement

405

Koaxialkabel unbekannter Länge

406

Einrichtung zur Lokalisierung von Impedanz-Fehlanpassungen

407

Verteilnetz

Figur 10

Weiteres Ausführungsbeispiel der Erfindung

501

Satelliten-Signal-Antenne

502

Mixer

503

Ausschnitt aus einem Verteilnetz unbekannter Netztopologie

504

Ableitungselement

505

Koaxialkabel unbekannter Länge

506

Einrichtung zur Lokalisierung von Impedanz-Fehlanpassungen

507

Verteilnetz

Description of the figures

FIG. 1

Detection of impedance mismatches

101, OE

Formation (acquisition) of the spectrum

102

Block of formation of the spectrum module

103

Noise reduction.

104

Transformation of the spectrum

105

Inverse Fourier transform of N points

106

Editing the time response

107

Normalization.

108, DM

Detection of maximum values

FIG. 2

Spektraltransformationsblock

1041

Block of squaring

1042

Block the transformation of the spectrum

FIG. 3

Block of processing the time response

1061

Block of formation of the spectrum module

1062

Block of squaring

FIG. 4

Components that result from the shape of the input signal

FIG. 5

Detecting the position of the impedance mismatches.

FIG. 6

SMATV network in which TV signals or any other known signal is measured

201

Satellite signal antenna

202

mixer

203

derivative components

204

distribution network

205

using sockets

206

localization device

207

coaxial

FIG. 7

Embodiment of the invention

301

Input terminal of the signal

302

Device for energy detection

303

mixer

304

Bandpass filter

305

Local oscillator for intermediate frequency signal

306

Automatic gain control circuit (AGC)

307

Analog-to-digital converter (A / D)

308

Microprocessor control

309

Interface with user

310

Optical terminal

311

FPGA

FIG. 8

Sets of satellite programs in the IF band FI

FIG. 9

Another embodiment of the invention

401

Satellite signal antenna

402

mixer

403

Section of a distribution network of unknown network topology

404

dissipation element

405

Coaxial cable of unknown length

406

Device for locating impedance mismatches

407

distribution

FIG. 10

Another embodiment of the invention

501

Satellite-signal antenna

502

mixer

503

Section of a distribution network of unknown network topology

504

dissipation element

505

Coaxial cable of unknown length

506

Device for locating impedance mismatches

507

distribution

Description of a preferred embodiment of the invention

Hereinafter, a preferred exemplary embodiment of the invention will be described without excluding other embodiments of the invention. The following description illustrates the features and advantages of the present invention with reference to one of many embodiments.

• Es zeigt

  Figur 6

  in vereinfachter Darstellung den Weg des Signals in einem SMATV-Netz bis zu dem erfindungsgemäßen System der Erkennung und der Lokalisierung von Fehlanpasungen;

  Figur 7

  ein Schema des Systems zur Erkennung und Lokalisierung von Fehlanpassungen gemäß der Erfindung;

  Figur 8

  ein Beispiel eines Spektrums, das zur Erkennung und Lokalisierung von Impedanz-Fehlanpassungen verwendet wird,

  Figur 9

  die Verwendung des erfindungsgemäßen Systems zur Messung der Länge eines Koaxialkabels; und

  Figur 10

  die Verwendung des erfindungsgemäßen Systems zur Erkennung der Entfernung zu einem Ausfall.

A non-limiting example of the preferred embodiment will now be described with reference to the following figures:

• It shows

  FIG. 6

  in a simplified representation of the path of the signal in a SMATV network to the system of detection and localization of Fehlanpasungen invention;

  FIG. 7

  a schematic of the system for detection and localization of mismatches according to the invention;

  FIG. 8

  an example of a spectrum used to detect and locate impedance mismatches,

  FIG. 9

  the use of the system according to the invention for measuring the length of a coaxial cable; and

  FIG. 10

  the use of the inventive system for detecting the distance to a failure.

FIG. 6 shows a simplified representation of an SMATV network in which the detection and localization of mismatches occurs. The block 201 corresponds to a satellite signal receiving antenna which positions the signal received in the IF band in the range between 950 and 2150 MHz. The signal from block 201 is mixed with a terrestrial TV signal and transmitted to the distribution network 204. The mismatches in the derivative components 203 and in the sockets 205 are summed to the input signal in the network 204, they are transmitted via the coaxial cable 207 to the system 206 for detection and localization of the mismatches.

FIG. 7 shows a schematic representation of the system of detection and localization of mismatches. The signal enters the system via 301. Block 302 is a power detector which serves to inform the module 308 which is receiving a signal at the input. The module 308 is at the heart of the system and its mission is to organize the steps that the other blocks that are part of the global system have to follow depending on user instructions displayed via the interface 309, as well as the steps of the system Power detector 302. The RF signal is converted to a known intermediate frequency by means of the oscillator 305 and the mixer 303. The bandpass filter 304 has the task of limiting the bandwidth used in the formation of the spectrum, whereby the signal corresponding to the adjacent frequencies is eliminated so that only the band of interest remains, which is digitized by the analog-to-digital converter 307.

In this application example of the invention, the gain level of the signal is previously adjusted with a gain control 306 so as to cover the entire dynamic range of the analog-to-digital converter and thus reduce the quantization errors. After digitization, the signal is passed to the system 311 where the necessary samples are taken to obtain the spectrum of the frequency range being used. After the samples are detected, one obtains their frequency response and this is communicated to system 308 using any appropriate communication slices. Not in this one By way of limitation, the system 311 is an FPGA (Field Programmable Gate Array).

The system 308 calculates the location of the impedance mismatches. Block 308 will also adjust the frequency of the signal to capture the signal, thus shaping the spectrum of the satellite band; an example of a resulting spectrum is in FIG. 8 shown.

The user of the present invention may communicate with the block 308 via the user interface 309.

FIG. 9 shows a situation in which the present invention is used. This illustration is not a limitation neither in terms of implementation nor scope of the present invention. The illustrated system measures the unknown length L of a cable 406 located in a SMATV network 407 in which there is an area 403 whose topology is not is known. The cable 406, as well as the system 406 for the detection and localization of mismatches are connected to a switch (divert) 404.

FIG. 10 shows, by way of example, a system that determines the unknown distance to the fault Lf within a cable 505 of length Lc located in an SMATV network 507. The network has a part 503 whose topology is unknown. The cable 505, as well as the system 506 for the detection and localization of mismatches are connected to a switch (lead-off) 504 ..

This preferred embodiment, which does not limit the implementation of the invention or the scope of the present invention, relates to a system for detecting and locating impedance mismatches in SMATV networks.

The system according to the invention is designed in such a way that input signals in an SMATV network are signals which are not input by or into the system from the outside.

System intrinsic signals are used to detect and locate impedance mismatches.

The invention also relates to a method for detecting and locating impedance mismatches in SMATV networks in a system as described above. According to the invention signals are used as input signals that are not input by or in the system from the outside.

Claims (8)

System for detecting and locating impedance mismatches in SMATV networks, which includes a radio frequency input (301), a means (302) for detecting energy, a mixing stage (303) for converting a predetermined signal to an intermediate frequency, a bandpass filter (304), an analog-to-digital converter (307) an automatic gain control circuit (306),
characterized,
that the system is designed in such a way that input signals in an SMATV network are signals that are not input by the system. System according to claim 1, characterized in that the system is designed in such a way that the input signals used are signals which are present in the SMATV network and in the frequency range in which signals are distributed in the network. System according to claim 2, characterized in that the system is designed in such a way that the resolution of the space recognition, the bandwidth used and the rank of the space recognition are varied. System according to one of the preceding claims, characterized in that the system is designed in such a way that the length (Lc) of a given coaxial cable within a SMATV network (407, 507) is measured. System according to one of the preceding claims, characterized in that the system is designed such that the distance (Lf) to the failure of coaxial cables (505) in SMATV networks is measured. System according to one of the preceding claims, characterized in that the system is designed in such a way that the results obtained in different measurements at various points of the SMATV network are compared with each other. System according to one of the preceding claims, characterized in that the system is designed in such a way that the difference of the corresponding spectra from different measurements at different points of the SMATV network are used as input signal. A method for detecting and locating impedance mismatches in SMATV networks in a system comprising a radio frequency input (301), a means (302) for detecting energy, a mixing stage (303) for converting a predetermined signal to an intermediate frequency, a bandpass filter (304), an analog-to-digital converter (307), an automatic gain control circuit (306),
characterized,
that signals which are not input by the system are used as input signals.

Images