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WO2000057571A1 - Localisation de defaillances dans un cable coaxial - Google Patents

Localisation de defaillances dans un cable coaxial Download PDF

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Publication number
WO2000057571A1
WO2000057571A1 PCT/AU2000/000235 AU0000235W WO0057571A1 WO 2000057571 A1 WO2000057571 A1 WO 2000057571A1 AU 0000235 W AU0000235 W AU 0000235W WO 0057571 A1 WO0057571 A1 WO 0057571A1
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WO
WIPO (PCT)
Prior art keywords
signal
signals
network
mhz
local oscillator
Prior art date
Application number
PCT/AU2000/000235
Other languages
English (en)
Inventor
Rodney Karl Eastment
Original Assignee
Cable & Wireless Optus Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Cable & Wireless Optus Ltd. filed Critical Cable & Wireless Optus Ltd.
Priority to AU32641/00A priority Critical patent/AU3264100A/en
Publication of WO2000057571A1 publication Critical patent/WO2000057571A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H04B3/02—Details
    • H04B3/46—Monitoring; Testing

Definitions

  • the present invention relates to the field of detecting hardware faults in a bi-direction network. It has particular but not exclusive application to the location of common path distortion (CPD) faults in a bi-direction cable network.
  • CPD common path distortion
  • Bi-directional coaxial cable networks and hybrid fibre coaxial cable networks provide services such as cable television and bi-directional telephony and data services.
  • Such networks provide bi-directionality on the basis of frequency multiplexing, with one band, for example, 5 - 65 MHz being used for upstream signals - that is to the exchange - and a further band, for example 85 - 750 MHz being used for downstream and broadcast signals.
  • filters are used to prevent the upstream band from propagating downstream, and vice versa.
  • a signal having a frequency within the downstream band cannot propagate to the end of the network and return, as filter diplexers within the amplifiers would prevent this.
  • interference arises due to unintentional non-linear elements occurring in the plant equipment.
  • plant equipment By plant equipment is meant the cables, gateways, amplifiers, customer taps, and other physical elements of the network.
  • the most common type of non-linear element results from corrosion occurring within connectors and joints, producing metal - metal oxide - metal junctions where signal rectification and intermodulation products arise.
  • These undesired intermodulation products substantially raise the system noise and degrade the performance of the plant in providing services to customers.
  • the noise may affect not only the branch of the network in which it occurs, but also neighbouring branches by decreasing the signal to noise ratio, for example, during upstream transmissions. This type of noise degradation is known as common path distortion (CPD) or passive intermodulation (PIM).
  • CPD common path distortion
  • PIM passive intermodulation
  • the present invention provides a method for detecting propagation time delay associated with one or more faults in a bidirectional network, including the steps of: a) introducing signals F1 and F2 into the downstream band of the network, F1 and F2 each having a defined modulation and specific frequency band, so that said signals propagate in the downstream band of said network; b) monitoring the upstream band to detect signal F3, where F3 is a selected mixing product of F1 and F2; c) correlate the detected F3 signal with F1 and F2 so as to determine the time delay associated with one or more CPD faults.
  • the network has been previously calibrated so as to determine the time delay associated with each node at a number of reference points relative to the test point.
  • a fourth step allows the range determination of the node in question, or with a suitably sophisticated mapping system, the location of the fault.
  • frequency F3 is the difference between frequencies F1 and F2.
  • the present invention may be employed from an exchange or cable head end, it may equally be deployed in a field unit so as to detect a fault in the field. It will be appreciated that it is not uncommon for there to be multiple faults in a node, and the present invention is capable of detecting separately located sources of CPD.
  • the principle of the present invention relies on the CPD acting as a mixing element of the transmitted signals. This produces a family of intermodulation products at each fault, some of which will fall within the upstream band.
  • the second order difference product F1 - F2 is detected within the upstream band at frequency F3. It is preferred that the frequencies selected are within reserved bands so as to not interfere with other services.
  • Figure 1 shows a schematic representation of an exemplary bidirectional information network.
  • Figure 2 is a simplified block diagram of a fault locating device according to a preferred form of the invention.
  • Figure 3 shows the spectral layout of signals in the network of figure 1.
  • Figure 4 is a block diagram of the up converter as used in the device of figure 2.
  • Figure 5 is a block diagram of the down converter as used in the device of figure 2.
  • Figure 6 is a frequency versus time plot of a frequency ramp chirp signal generated by the device of figure 2.
  • Figure 7 is a frequency versus time plot of the chirp signal of figure 6 to show the effect of temperature on the accuracy of the range measurement derived.
  • the bidirectional network 100 of figure 1 can provide cable television and bidirectional telephony and data services between an exchange 101 and many end users 102.
  • the network may consist of several sub-networks to suit its particular purpose.
  • network 100 consists of an optical fibre network (region A), and a coaxial cable network (region B). This is known as a Hybrid Fibre Coaxial (HFC) network.
  • HFC Hybrid Fibre Coaxial
  • Exchange 101 includes a transmitter 101 a and a receiver 101 b.
  • Optical signals are sent down fibre 103 through gateway 104 where the signals are converted to radio frequency signals for transmission over the coaxial cable network (region B).
  • multiple tap junctions 106 Disposed over a stretch of cable 105 are multiple tap junctions 106 which "tap off" the signal from the main cable 105 to connect to an end user 102. Also disposed over a stretch of cable are multiple line amplifiers 107 which continually amplify the signal being transmitted to counter its degradation due to energy losses occurring during its propagation along cable 105.
  • the forward (downstream) signals are spectrally separated from the return (upstream) signals.
  • This spectral separation is represented in figure 3, where the region denoted 300 is the bandwidth allocated to the downstream signals, and the region denoted 305 is the bandwidth reserved for upstream signals.
  • the region 301 denotes the bandwidth typically taken up by the video, telephone and data signals distributed over the network. Region 301 may also be interspersed between f-
  • Filter diplexes (not shown) within the line amplifiers 107 are also distributed throughout network 100 to prevent signals having downstream frequencies from propagating upstream and vice versa, enabling bi-directional amplification.
  • faults can occur in any portion of network 100 where there are many connectors or joints. If corrosion occurs within a connector or joint, a non-linear element is produced, which can result in signal rectification and intermodulation products. Intermodulation products substantially raise the system noise and degrades the performance of services. Due to the literally thousands of junctions 106, in a typical network 100, a fault arising in one junction, for example 106a can be extremely difficult to locate.
  • CPD Common Path Distortion
  • Locator 200 generates two test signals at frequencies f-i and f respectively, both having frequencies within the bandwidth allocated for downstream signals. These two test signals are represented in figure 3 as 302 and 303 respectively. Note that frequencies fi and f 2 are spectrally separated from the bandwidth 301 normally used by the normal traffic to avoid interference.
  • and f 2 propagate down network 100 through fibre 103, are converted to radio frequency signals in gateway 104, and are distributed throughout cable network 105.
  • signals and f 2 Upon reaching tap junction 106a, which exhibits non-linear characteristics due to a fault, signals and f 2 produce intermodulation products of various orders including a second order difference product f 3 .
  • Signals fi and f 2 are selected so that second order difference product f 3 is centred about a frequency falling within the bandwidth allocated for upstream signals.
  • Second order difference product f 3 (return signal) is denoted in figure 3 as 304. It can be seen that it lies within upstream bandwidth 305.
  • Return signal f 3 propagates upstream towards exchange 101 where it is detected by fault locator 200.
  • Locator 200 essentially measures the time difference in the modulation of return signal f 3 with respect to the modulation of original test signals fi and f 2 . A distance between exchange 101 and a fault at junction 106a is determined by this time difference, thus facilitating the location of the fault, or the source of the CPD.
  • An actual position and distance is achieved by comparing the measured time with a database containing calibrated times together with their corresponding node positions.
  • This database is built up by using a Range Calibrator, which is used to measure and calibrate the return delay to specific points in the coaxial cable portion of the HFC network 100.
  • the Calibrator is a field mobile test box which is connected to customer tap points, preferably close to the downstream outputs of line amplifiers. A log book is maintained for each node of the return calibration delays to known points. These serve as markers to produce a "range map" of the network, and will enable CPD faults to be reasonably accurately located to within limited portions of the coaxial cable when they are detected.
  • the range calibrator mixes the 2 ranging signals (at 681.5 MHz and 741 MHz) and injects the 2-carrier mixed product at 59.5 MHz into the upstream spectrum.
  • This return product is band pass filtered to limit its spectrum to 57 - 62 MHz.
  • the Calibrator includes a line phase timing control which enables the return 59.5 MHz upstream signal to be pulsed on (for 2.5 ms) and adjusted to lie in a suitable position within the 20 ms line period. By doing this, it enables the return signal to be moved away in "phase time” from a real CPD fault enabling the range to each to be independently measured should they be at the same spatial location.
  • a ranging measurement will not uniquely locate the fault.
  • the faulty branch or leg will have to be located by signal tracing.
  • the ranging resolution of the order of a few metres assists in CPD location, since faults mostly occur at tap junctions 106 or line amplifiers 107 and not in mid-span. This accuracy enables candidate branches 105 to be rejected where faults would be placed in mid-span sections.
  • return signal f 3 be a difference product of f-i and f 2 .
  • return signal f 3 may be the sum product of f-i and f 2 , or any other suitable product.
  • Fault locator 200 uses a batch sample signal processing software.
  • the program interfaces through an internal computer bus 202 to an arbitrary waveform generator (AWG) 201 and a high speed analog to digital sampling card (A to D) 208.
  • AWG 201 becomes the signal generator and A to D 208 the receiver.
  • Custom designed and built frequency conversion equipment 213 interfaces between the AWG / A to D and the network 100 to shift signals into the correct spectrums.
  • Measurement signals are generated by software and loaded into AWG 201 which is set up to generate signals in the band 3.75 to 6.25 MHz.
  • the fault location, procedure involves two steps. There is firstly an initialisation step, followed by the actual measurement step.
  • the initialisation step is used to determine the timing of triggering signals to A to D 208 such that it will only take samples when the CPD pulse is present. It has been found that the CPD is amplitude modulated at the supply line rate, pulsed on, lasting around 2 milliseconds during each cycle or half mains cycle.
  • a continuous wave (CW) signal is output at 5.35015 MHz. It is sent as a series of 184 bursts lasting for 301.4 ms.
  • this initialisation step is only necessary in the case where the CPD is in fact modulated by an external signal.
  • 90V AC, 50Hz power is supplied through the coaxial cable 105, which modulates any CPD signals.
  • a different initialisation step may be required to suit the particular type of modulation of the CPD pulses.
  • a frequency ramp chirp signal which linearly ramps from 3.75 to 6.25 MHz is generated. This signal is synthesised in 32768 points clocked at 20 MHz. One complete cycle, called a burst, lasts for 1.6384 milliseconds. Multiple bursts are utilised.
  • the AWG 201 signal is sent to up converter 500 which produces two output signals fi and f 2 separated by nominally 59.5 MHz. One signal is spectrally erect, while the other is spectrally inverted. These signals are injected (218) into network 100 and propagate through the network until they reach fault 106a, producing a family of intermodulation products.
  • f-i - f 2 (element 304 in figure 3).
  • This second order product (f 3 ) will carry double frequency modulation of the f
  • Down converter 400 converts a 57 to 62 MHz band (containing f 3 at 59.5 MHz) to 7.5 to 12.5 MHz and sends this to A to D 208.
  • Low pass filter (6.5 MHz) 203 suppresses alias clock products from AWG 201.
  • Hybrid transformers 204, 206 and 207 provide for signal splitting or summing.
  • the sampling of this signal by the A to D is controlled by software and employs a 2-pulse interleaved sampling technique (published in IREE Vol. 18, June 1998) using 25 nanosecond delay line 212.
  • the two interleaved samples are down loaded to PC 209, where the signal processor software converts the sampled 10 MHz signal into a complex baseband spectrum.
  • the A to D sampling is initiated with the external trigger signal from the timing box 216.
  • An internal delayed trigger equal to one burst (1.6384 ms) is used to allow for the network propagation delay. When sampling chirps using a 5 MHz sample clock, this results in the tail end of burst 1 being followed by the first part of burst 2. Since all bursts are identical, this equates to a time-wrapped alias sample signal. If the delayed trigger were not used, the leading portion of the sample would have no signal.
  • a to D 208 samples the signal generated by AWG 201 is CW.
  • the chirp signal may be represented by Re jW(t)t , where R indicates the real part.
  • the first component in the exponent is a frequency shift proportional to the delay ⁇ .
  • the second component is a fixed phase roll dependent on the delay ⁇ .
  • the "de-chirped" signal is then Fast Fourier Transformed (FFT) to reveal
  • Software locates spectral peaks derived from the FFT which are above a set threshold value, and performs narrow bandwidth (2 kHz) gaussian filtering, followed by phase roll demodulation.
  • the exact filter bandwidth is set to be commensurate with the sampling, i.e. an integer multiple of the resolution bandwidth.
  • the phase roll is measured using a least squares method. This provides accurate sub-FFT element frequency resolution which permits range determinations to better than 1 metre, dependent on the CPD return C/No (carrier to Noise density per hertz).
  • a to D 208 is synchronously triggered with AWG 201 via an external trigger signal from timing box 216.
  • This synchronous triggering ensures that chirp samples occur when the CPD signal is maximum. It also enables coherent vector summation of multiple chirp signals, improving the signal to noise ratio (S/N) of CPD returns.
  • Signal to noise improvement is directly related to the number of coherent detections. Ten coherent detections improves S/N by 10 dB and 100 detections improves S/N by 20 dB.
  • a frequency doubled reference 205 (figure 2) derived from the AWG signal is added to the down converter 214 output signal. This reference is equivalent to a zero delay CPD return.
  • the software filters, phase demodulates and measures its phase roll. This is used to reference the absolute timing for the whole sample and removes external trigger timing jitter introduced by the sampler. This reference is only applied during the chirp range measurement.
  • the signal processing software used by locator 200 generates the ranging test signals through AWG 201 and processes the return samples to compute the return delay. Once the test signal is generated and loaded into AWG 201 , no further signal processing is required for signal transmission.
  • the return signals are sampled by a digital sampler and passed on to the processor 209 via bus 21 1 where they are batch processed.
  • successive samples are complex voltage summed, producing a coherent summation with improved signal to noise which improves ranging accuracy.
  • the software also provides graphing and printing, filing, and retrieval of measurement samples.
  • a distance calculator is also provided to assist the operator to convert the difference between return calibrations and CPD ranges into a distance with allowances for delay through line amplifiers. This facility greatly assists the operator in choosing the most likely candidate branch from several options due to network branching.
  • Up-converter 400 of frequency conversion equipment 213 is shown in figure 4. It is designed to convert a 5 MHz signal to an erect and an inverted spectrum pair of signals, at the desired frequencies. In this case the respective frequencies will be at 681.5 and 741 MHz, which lie at the upper spectrum end of the HFC downstream spectrum 300.
  • Local oscillator 401 is at 24.75 MHz, which mixes the input signal up to 29.75 MHz.
  • Bandpass filter 402 filters out the lower component and passes the 29.75 MHz signal onto local oscillator 403 which is at 711.25 MHz. This mixes with the 29.75 MHz signal to produce an upper and a lower sideband pair of signals, the lower sideband at 681.5 MHz and the upper sideband at 741 MHz. Any frequency errors in the second local oscillator 403 are inconsequential since the difference frequency between the upper and lower sideband signals remains constant at 59.5 MHz. As discussed above, this difference frequency will result in the CPD signal having a frequency of 59.5 MHz, allowing it to propagate through the network as a return signal.
  • the upper sideband U (or f 2 as previously referred to) may be represented as:
  • the lower sideband L (or fi as previously referred to) as:
  • the intermodulation difference product D (or f 3 as previously referred to) is then: n - R ⁇ J[(2W l01 t+2Wint-2W l01 . ⁇ dn-2Win. ⁇ dn)]
  • Down converter 500 receives this return signal D (or f 3 ) after the upstream delay ⁇ up at 59.5 MHz.
  • the 2-carrier mixing action of the CPD fault causes the frequency chirp to have twice the original AWG bandwidth input to the up converter 400.
  • Down converter 500 mixes signal f 3 with its local oscillator 502, at 49.5 MHz.
  • Oscillator 502 is derived by frequency doubling up converter 400's first local oscillator 401 and is coherently locked to it. Thus, any frequency errors in local oscillator 401 will be effectively removed in the return signal f 3 as it is frequency doubled by the same amount.
  • the proviso is that the local oscillator frequency remains phase coherent to within a few degrees over a period of up to 500 microseconds which is the order of the maximum 2-way return delay to the CPD fault.
  • Down converter 500 has two selectable IF filter bandwidths, one for each measurement signal. For the CW signal, the filter is 25 kHz bandwidth centred at 10.7 MHz. For the chirp signal, the filter is 5 MHz bandwidth centred at 10.0 MHz i.e. 7.5 to 12.5 MHz.
  • signal D (or f 3 ) is received.
  • Signal D has now travelled from the CPD fault to the locator 200, taking time ⁇ up. thus signal D at input 504 is:
  • the local oscillator after network propagation delay will have phase roll.
  • Down converter 500 subtracts the local oscillator, hence the negative frequency component is used.
  • the down converter output is precisely frequency doubled the input signal to the up converter with the network propagation delay.
  • ⁇ F is the frequency measurement uncertainty due to noise
  • ⁇ T is the time measurement uncertainty
  • a ⁇ T of 1.36 ns equates to 0.18 metres.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Two-Way Televisions, Distribution Of Moving Picture Or The Like (AREA)
  • Locating Faults (AREA)

Abstract

Cette invention a trait à une méthode, ainsi qu'au dispositif correspondant, permettant de localiser des défaillances dans un réseau à câble bidirectionnel, des bandes de fréquences distinctes étant utilisées aux fins d'une propagation des signaux vers l'amont et vers l'aval. Cette méthode convient particulièrement à la localisation de distorsion de trajet commun ou de défaillances de l'intermodulation à l'état passif. Les signaux se propagent dans la bande aval avec des modulations définies et à des fréquences choisies, de sorte qu'une défaillance réseau renverra un signal renfermant un produit du mélange choisi des signaux avals. Ces signaux avals sont choisis de manière que le produit du mélange soit dirigé vers la bande amont, de sorte que le signal renvoyé puisse retourner vers la source et être mis en corrélation avec les signaux avals. L'invention concerne également un dispositif.
PCT/AU2000/000235 1999-03-24 2000-03-23 Localisation de defaillances dans un cable coaxial WO2000057571A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU32641/00A AU3264100A (en) 1999-03-24 2000-03-23 Coaxial cable fault locator

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AUPP9410A AUPP941099A0 (en) 1999-03-24 1999-03-24 Coaxial cable fault locator
AUPP9410 1999-03-24

Publications (1)

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WO2000057571A1 true WO2000057571A1 (fr) 2000-09-28

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TW (1) TW474071B (fr)
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Cited By (14)

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WO2006091708A3 (fr) * 2005-02-22 2006-12-21 Arcom Digital Llc Procédé et appareil de localisation de distorsion de voie commune
US7415367B2 (en) 2003-05-20 2008-08-19 Arcom Digital, Llc System and method to locate common path distortion on cable systems
DE102010015103A1 (de) * 2010-04-16 2011-10-20 Rosenberger Hochfrequenztechnik Gmbh & Co. Kg Verfahren zum Orten von fehlerhaften Stellen in einem HF-Signalübertragungspfad
DE102010015102A1 (de) * 2010-04-16 2011-10-20 Rosenberger Hochfrequenztechnik Gmbh & Co. Kg Verfahren zum Orten von fehlerhaften Stellen in einem HF-Signalübertragungspfad
DE102010046099A1 (de) * 2010-09-21 2012-03-22 Rohde & Schwarz Gmbh & Co. Kg Verfahren und System zur Ermittlung des Entstehungsortes von passiven Intermodulationsprodukten
US8548760B2 (en) 2008-09-17 2013-10-01 Jds Uniphase Corporation Detecting nonlinearity in a cable plant and determining a cable length to a source of the nonlinearity
WO2014012585A1 (fr) * 2012-07-18 2014-01-23 Nokia Siemens Networks Oy Détection de l'intermodulation d'une communication à bande large affectant la sensibilité du récepteur
WO2016065094A1 (fr) * 2014-10-22 2016-04-28 Arcom Digital, Llc Détection de cpd dans un réseau à fibre coaxiale hybride (hfc) avec des signaux mrof
US9960842B2 (en) 2015-10-12 2018-05-01 Arcom Digital, Llc Network traffic-compatible time domain reflectometer
US10616622B2 (en) 2018-06-06 2020-04-07 Arcom Digital Patent, Llc Detection of CPD from signals captured at remote PHY device
US10911163B2 (en) 2017-03-16 2021-02-02 Ranplan Wireless Network Design Ltd Locating passive intermodulation fault sources
CN112729884A (zh) * 2020-12-22 2021-04-30 河北建设投资集团有限责任公司 基于大数据的设备故障诊断方法及装置
CN113169758A (zh) * 2018-10-22 2021-07-23 直接天线控制系统有限公司 用于同轴传输线的故障检测系统
US11082732B2 (en) 2019-08-07 2021-08-03 Arcom Digital Patent, Llc Detection of CPD using leaked forward signal

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CN110412427B (zh) * 2019-08-21 2024-08-30 广东聚贤盛邦智能制造科技有限公司 一种低压电力故障检测定位系统及故障检测方法

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US7415367B2 (en) 2003-05-20 2008-08-19 Arcom Digital, Llc System and method to locate common path distortion on cable systems
US7788050B2 (en) 2003-05-20 2010-08-31 Arcom Digital, Llc System and method to locate common path distortion on cable systems
US7584496B2 (en) 2005-02-22 2009-09-01 Arcom Digital, Llc Method and apparatus for pinpointing common path distortion
WO2006091708A3 (fr) * 2005-02-22 2006-12-21 Arcom Digital Llc Procédé et appareil de localisation de distorsion de voie commune
US8548760B2 (en) 2008-09-17 2013-10-01 Jds Uniphase Corporation Detecting nonlinearity in a cable plant and determining a cable length to a source of the nonlinearity
DE102010015103A1 (de) * 2010-04-16 2011-10-20 Rosenberger Hochfrequenztechnik Gmbh & Co. Kg Verfahren zum Orten von fehlerhaften Stellen in einem HF-Signalübertragungspfad
DE102010015102A1 (de) * 2010-04-16 2011-10-20 Rosenberger Hochfrequenztechnik Gmbh & Co. Kg Verfahren zum Orten von fehlerhaften Stellen in einem HF-Signalübertragungspfad
US9391719B2 (en) 2010-09-21 2016-07-12 Rohde & Schwarz Gmbh & Co. Kg Method and a system for determining the place of origin of passive intermodulation products
DE102010046099A1 (de) * 2010-09-21 2012-03-22 Rohde & Schwarz Gmbh & Co. Kg Verfahren und System zur Ermittlung des Entstehungsortes von passiven Intermodulationsprodukten
CN104471881A (zh) * 2012-07-18 2015-03-25 诺基亚通信公司 检测影响接收机灵敏度的在宽带通信中的互调
US20150358144A1 (en) * 2012-07-18 2015-12-10 Marko Fleischer Detecting Intermodulation in Broadband Communication Affecting Receiver Sensitivity
CN104471881B (zh) * 2012-07-18 2016-12-14 诺基亚通信公司 检测影响接收机灵敏度的在宽带通信中的互调
WO2014012585A1 (fr) * 2012-07-18 2014-01-23 Nokia Siemens Networks Oy Détection de l'intermodulation d'une communication à bande large affectant la sensibilité du récepteur
US10897341B2 (en) 2012-07-18 2021-01-19 Nokia Solutions And Networks Oy Detecting intermodulation in broadband communication affecting receiver sensitivity
WO2016065094A1 (fr) * 2014-10-22 2016-04-28 Arcom Digital, Llc Détection de cpd dans un réseau à fibre coaxiale hybride (hfc) avec des signaux mrof
US9826263B2 (en) 2014-10-22 2017-11-21 Arcom Digital, Llc Detecting CPD in HFC network with OFDM signals
US9960842B2 (en) 2015-10-12 2018-05-01 Arcom Digital, Llc Network traffic-compatible time domain reflectometer
US10911163B2 (en) 2017-03-16 2021-02-02 Ranplan Wireless Network Design Ltd Locating passive intermodulation fault sources
US10616622B2 (en) 2018-06-06 2020-04-07 Arcom Digital Patent, Llc Detection of CPD from signals captured at remote PHY device
US11290761B2 (en) 2018-06-06 2022-03-29 Arcom Digital Patent, Llc Detection of CPD from signals captured at remote PHY device
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