Abstract: Most researchers in the Power Line Communications (PLC) field have adopted the practice of using idealized impulse noise models directly at the input of the demodulator, as is widely done in simulations. The effect of the coupling circuit on the impulse noise tend to be ignored. However, coupling circuits produce transients. This paper focuses on investigating the effect of the coupling circuit on the impulse noise. Experimental measurements are used to determine the effect of the coupling circuit. An equivalent circuit of the coupling circuit is developed and further simulations are conducted to gain in-depth knowledge on how the impulse noise is affected by the coupling circuit. A literature survey suggests that this topic has not been studied yet

De Beer,, A.S.

Ferreira, Hendrik C.

Samakande, T.

Shongwe, T.

English

University of Johannesburg Institutional Repository

The Effect of Coupling Circuits on Impulsive Noisein Power Line CommunicationT. Samakande, T. Shongwe, A.S. de Beer, H.C. FerreiraDepartment of Electrical and Electronic Engineering ScienceUniversity of Johannesburg, P. O. Box 524,Auckland Park, 2006, South AfricaAbstract—Most researchers in the Power Line Communica-tions (PLC) field have adopted the practice of using idealizedimpulse noise models directly at the input of the demodulator, asis widely done in simulations. The effect of the coupling circuit onthe impulse noise tend to be ignored. However, coupling circuitsproduce transients. This paper focuses on investigating the effectof the coupling circuit on the impulse noise. Experimental mea-surements are used to determine the effect of the coupling circuit.An equivalent circuit of the coupling circuit is developed andfurther simulations are conducted to gain in-depth knowledgeon how the impulse noise is affected by the coupling circuit. Aliterature survey suggests that this topic has not been studiedyet.Keywords—PLC, Power Line Communication, Impulse noise,Coupling circuit, Band-pass filter.I. INTRODUCTIONNoise is one crucial factor that affects any communicationsystem. Different classes of noise are experienced in PLCsystems which disturb transmitted signals. The various sourcesof noise are classified as narrow band noise, background noiseand impulsive noise [1]. Unlike many other communicationsystems, the noise in a Power Line Communication environ-ment cannot be described only by an additive white Gaussiannoise (AWGN) model [2]. This leads to a greater need tothoroughly investigate and analyze these different classes ofnoise in order to come up with a reliable model.Most PLC research over the years has confirmed throughpractical measurements that impulsive noise has the most de-grading/distorting effects to communication signals comparedto other types of noise [3], [4], [5]. It is therefore imperative toacquire more knowledge and understanding of impulsive noiseand its effect on communication over power line channel, inparticular when coupling circuits are used. In order to transmitor receive any signal from power lines a coupling circuit isutilized. The purpose of the coupling circuit is to block thelow frequency, high voltage/current signal from the power lineside and allow the high frequency and low voltage/currentcommunication signal to pass through [6]. Understanding howthe coupling circuit affects or changes the impulsive noisepassing through it from the power line is of crucial importance.Practically measuring the different characteristics of impulsenoise and its impacts as it passes through a coupling circuitwill provide results to help gain in-depth knowledge on howimpulse noise affect PLC performance and in designing betterPLC systems. Investigating the effect of coupling circuits onimpulsive noise will also help to understand and possiblymodify or validate/invalidate the practice of using idealizedimpulse noise models (usually Middleton Class A) directly atthe input of the demodulator, as is widely done in simulations.A search of the published literature suggests that the effectof coupling circuits on impulse noise has not been studiedyet. This investigation focuses on determining the effect ofcoupling circuits on impulsive noise. In this paper, the termsimpulse noise and impulsive noise will be used interchange-ably.This paper is organized as follows. Section II describes theexperimental set-up and environment that was used for mea-surements. Also, the coupling circuit used in all the measure-ments is described. In section III, the measurement results andanalysis are presented. An approximate equivalent circuit ofthe coupling circuit is discussed in section IV. Section V dealswith the simulations conducted on the equivalent circuit of thecoupling circuit.II. MEASUREMENT SET UP AND HARDWAREA. Measurement set-upCareful considerations were made to come up with the bestconfiguration to conduct the impulse noise measurements. Fig.1 illustrates the experimental set-up. It shows the connectionsof the power cables from the Low Voltage (LV) transformer tothe measuring equipment. This set-up was crucial to minimizeground loops as this is one of the major challenges that is facedwhen conducting noise measurements. To determine the effectof the coupling circuit on the impulse signal a clean 50Hzmains signal is required. To achieve this, a Line ImpedanceStabilization Network (LISN) was used to filter out all externalRF noise that may affect our measurements. The isolationtransformer with ratio 1:1 was utilized to provide galvanicisolation to humans and electrical equipment for improvedsafety. A digital storage oscilloscope was used to capture thetime domain data from our measurements.B. Coupling circuitAll measurements were conducted using an off-the-shelfcoupling circuit for the Narrow Band Power Line Commu-nication Shield called the Mamba board [7]. See Fig. 2 forthe schematic diagram. In order to perform measurements theFig. 1. Measurement set-up.coupling circuit was isolated by cutting off the PCB tracks thatjoined the coupling circuit to the rest of the Mamba Board.C. Measurement approachHaving some control on the impulsive noise generated inour measurements was crucial. The LISN was utilized toisolate the individual electronic devices that generated thenoise allowing noise measurements of the particular device inits different states of operation. This allows test repeatabilityand easier interpretation of results. The ON-OFF and OFF-ONstatus was used to generate impulsive noise on all the devicesfor our measurements. The following devices were used togenerate the impulsive noise for the measurements:• 100Ω load with on/off switch• Fan / heater• Hair dryerImpulsive noise measurements were taken before and afterthe coupling circuit to determine its effect on the noise. AX100 probe was used to measure the impulse noise before thecoupling circuit. It is crucial to note that even though the LISNwas used, the 50Hz mains signal was not a perfect sinusoide.Fig. 2. Coupling circuit schematic.III. MEASUREMENT RESULTS AND ANALYSISFig. 3 shows the transfer function of the coupling circuit.According to the results, the transfer function shows theoccurrence of two resonant points which are around 5kHzand 200kHz. The input impedance graph in Fig. 4 furtherconfirms the existence of resonant points that are occurring inthe coupling circuit. This phenomena plays a very importantrole in affecting high frequency signals that pass through thecoupling circuit as shall be revealed with more results inthis section. Resonance has adverse effects in PLC couplingcircuitry and in most electronic technologies [8]. In the circuitin Fig. 2, the capacitor C1, inter-winding capacitance andwinding inductance of the transformer cause resonance in thecoupling circuit. It occurs when the magnetic energy stored inthe inductance and the electric energy stored in the capacitorsare transferred to and from, between these components [9].Fig. 3. Coupling circuit transfer function.The impulse noise generated by the 100Ω load with on/offswitch, fan/heater and Hair dryer were also captured in timedomain. It was observed that the 100Ω load and fan/heaterdid not produce impulse noise during normal operation. Theimpulsive noise was detected using the trigger level method.The measured results show that the coupling circuit has aneffect on the generated impulsive noise signal when it passesthrough it (See Fig. 5- Fig. 8). Before the coupling circuitthe impulse noise is superimposed on the 50Hz mains signaland after the coupling circuit the 50Hz signal is blocked.The results show that the coupling circuit introduces ringingFig. 4. Coupling circuit input impedance graph.resulting from the impulsive noise signal. The ringing slowlydampens out.Fig. 5. Measured results from the 100 Ω resistor with on/off switch.Fig. 6. Enlarged measured results from the 100 Ω resistor with on/off switch.As the impulse signal passes through the coupling circuit,it excites the resonant points of the coupler resulting inresonance which introduces ringing. This changes the timedomain parameters of the impulsive signal namely the impulseamplitude, duration and inter-arrival time [10], [11], as isevident from the results obtained. Time domain parametershave the most adverse effects on data transmission on powerlines. Most of the impulsive noise models in literature weredeveloped based on long time experimental measurementsin specific power line networks in which electrical deviceswere connected randomly [1], [10], [12]. Recently in [13],Fig. 7. Measured results from the fan/heater.Fig. 8. Measured results from the the hair dryer.the statistical information of the impulsive noise time domainparameters were used to characterize and model it. It is crucialto factor in the effects of the coupling circuit on the impulsivenoise when characterizing and developing models.A. Coupler equivalent circuitThe coupling circuit is fundamentally a band-pass filter.It allows a specific band of frequencies to pass throughwhile blocking the rest. The one used in this research wasa narrowband coupling circuit. In order to further understandthe effects of the coupling circuit to impulsive noise anequivalent circuit was designed in the form of a band-passfilter which allowed a frequency band of 3kHz-150kHz. UsingSpice simulation software (Multisim) a guided Trial and errormethod was used to come up with a filter that has a transferfunction approximately similar to that of the coupling circuitin question. Fig. 9 shows the obtained equivalent circuit ofthe coupling unit as a whole. The obtained circuit was a highimpedance circuit which is one of the many outcomes thatcould have been obtained through the trial and error method.IV. SIMULATIONA. Bode plotsIn this research, the coupling circuit in Fig. 2 was simulatedwith Spice simulation software (Multisim). Fig. 10 and Fig. 11show the transfer function and phase plot obtained from thesimulations. PCB track effects were assumed to be negligiblesince we were mainly focusing at frequencies below 1MHz.Fig. 9. Coupler equivalent circuit.Fig. 10. Simulated transfer function of coupling circuit.Fig. 11. Simulated phase plot of coupling circuit.It is evident that resonance occurred in the simulatedcoupling circuit at a frequency of approximately 6kHz and350kHz. Similarly the coupler equivalent circuit in Fig. 9was simulated and the transfer function and phase plot wereobtained as shown in Fig. 12 and Fig. 13. The bode plots forthe coupling circuit and its equivalent circuit are approximatelythe same. Since the equivalent circuit closely approximatethe experimental coupling circuit, further simulations wereconducted on the equivalent circuit.B. SimulinkIn this section random impulsive noise was generated inMatlab. The generated noise on the 220V mains represents thewidely used Middleton Class A noise because it has randomFig. 12. Simulated transfer function of coupler equivalent circuit.Fig. 13. Simulated phase plot of coupler equivalent circuit.occurrence and amplitude [14]. The produced random impulsenoise was used as the input to the coupler equivalent circuitand the output was measured. Fig. 14 represents the gener-ated impulse noise. The coupler equivalent circuit introducesringing to the impulse noise. Fig. 15 shows the output ofthe coupler equivalent circuit. The output shows that whenan impulse occurs the equivalent circuit introduces ringingor a burst of impulses. The resulting output noise is in theshape of damped sinusoids. See Fig. 16 for the enlarged partenclosed by the rectangle in Fig. 15. These results correspondto the experimental results as they both show how the couplingcircuit introduces ringing to the impulsive noise thus distortingits time domain parameters.V. CONCLUSIONIn this contribution, the effect of coupling circuits on theimpulse noise was investigated. Experimental measurementsand simulations have shown that the coupling circuit intro-duces ringing to impulse noise. This affects the time domainparameters of the impulse noise which have the most adverseeffects to data transmission on power lines. In addition, thisinvestigation also revealed the occurrence of resonance in thecoupling circuit which causes ringing on the impulse noise.Through this research it has been demonstrated that couplingcircuits have an effect on impulse noise and these effects mustbe taken into consideration. For generality of the obtainedFig. 14. Generated random impulse noise (Middleton Class A).Fig. 15. Equivalent circuit output impulse noise.Fig. 16. Enlarged output impulse noise.results, more measurements will be conducted on different setsof coupling circuits in future work.REFERENCES[1] G. Avril, M. Tlich, F. Moulin, A. Zeddam, and F. Nouvel,“Time/frequency analysis of impulsive noise on powerline channels,”in Home Networking. Springer, Boston, MA, 2008, pp. 143–150.[2] L. Di Bert, P. Caldera, D. Schwingshackl, and A. M. Tonello, “On noisemodeling for power line communications,” in 2011 IEEE InternationalSymposium on Power Line Communications and Its Applications (IS-PLC), April 2011, pp. 283–288.[3] T. Shongwe, A. J. H. Vinck, and H. C. Ferreira, “The effects of periodicimpulsive noise on ofdm,” in 2015 IEEE International Symposium onPower Line Communications and Its Applications (ISPLC), March 2015,pp. 189–194.[4] J. Ha¨ring and A. H. Vinck, “OFDM transmission corrupted by impulsivenoise,” in 2000 IEEE International Symposium on Power Line Commu-nications and Its Applications (ISPLC), Apri 2000, pp. 9–14.[5] Y. Ma, P. So, and E. Gunawan, “Performance analysis of OFDM systemsfor broadband power line communications under impulsive noise andmultipath effects,” IEEE Transactions on Power Delivery, vol. 20, no. 2,pp. 674–682, 2005.[6] L. G. da Silva Costa, A. C. M. de Queiroz, B. Adebisi, V. L. R. da Costa,and M. V. Ribeiro, “Coupling for power line communications: A survey,”Journal of Communication and Information Systems, vol. 32, no. 1,2017.[7] “Communica (Pty) Ltd,” 2017, (Accessed Nov 10,2017). [Online].Available: http://www.communica.co.za/catalog/Details/P3753604872[8] P. J. Janse van Rensburg, “Effective coupling for power-line communi-cations,” Ph.D. dissertation, University of Johannesburg, 2008.[9] C. Bowick, RF circuit design, 2nd ed. Newnes, 2011.[10] M. Zimmermann and K. Dostert, “Analysis and modeling of impulsivenoise in broad-band powerline communications,” IEEE transactions onElectromagnetic compatibility, vol. 44, no. 1, pp. 249–258, 2002.[11] M. H. Chan and R. W. Donaldson, “Amplitude, width, and interarrivaldistributions for noise impulses on intrabuilding power line communi-cation networks,” IEEE Transactions on Electromagnetic Compatibility,vol. 31, no. 3, pp. 320–323, 1989.[12] V. B. Balakirsky and A. H. Vinck, “Potential limits on powerlinecommunication over impulsive noise channels,” in Proc. 7th Int. Symp.Power-Line Communications and Its Applications (ISPLC), March 2003,pp. 32–36.[13] F. Rouissi, A. J. H. Vinck, H. Gassara, and A. Ghazel, “Statisticalcharacterization and modelling of impulse noise on indoor narrowbandplc environment,” in 2017 IEEE International Symposium on Power LineCommunications and its Applications (ISPLC), April 2017, pp. 1–6.[14] T. Shongwe, A. H. Vinck, and H. C. Ferreira, “On impulse noise and itsmodels,” in Power Line Communications and its Applications (ISPLC),2014 18th IEEE International Symposium on, March 2014, pp. 12–17.

The effect of coupling circuits on impulsive noise in power line communication

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The effect of coupling circuits on impulsive noise in power line communication

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