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I'm an electronics and communications engineering student undertaking a project regarding the occurrence of Electromagnetic Interference (EMI) in power line communications (PLC).

I would like to ask if anyone has any suggestions on how to do a performance analysis of a PLC modem that makes use of Orthogonal frequency-division multiplexing (OFDM). Specifically, how to measure its signal strength against the noise present in the system.

Your responses are greatly appreciated.

Anindo Ghosh
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Eager Engineer
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  • I've tried using an oscilloscope and a VOM by connecting probes in different spots inside the modem's PCB. However, I'm not sure whether i'm seeing the actual data signal or just the regular AC signal of the power line because I mostly get a voltage reading of around 220 volts, a frequency reading of around 60 Hz, and a sinusoidal waveform. –  May 02 '12 at 02:49
  • What modem are you using? If you are using TI's powerline modem we could have some discussions going ;) I am going to do almost exactly the same thing, so please shout out – chwi Nov 19 '12 at 12:06
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    Do you have a model for the noises present on the AC lines? Are you literally looking for signal levels and noise levels or the more abstract (but useful) ability to send data and resend packets that arrived corrupted? – Andy aka May 04 '13 at 20:48

2 Answers2

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Try leading the AC wiring through a large coil with e.g a 200Hz signal with a fair amplitude (depending on the coil size). This way you know that you have a 200Hz inductive noise signal and can look at how this influence your signal.

chwi
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TI and Maxim's demo kits have quite a bit of info about signal / noise, but you can't see what's happening. To be able to see EMI noise, a MFA 400 / MFA 600 from SweMet gives a pretty good picture, but it's a field instrument and not a lab instrument. Also, it's only for the CENELEC frequencies, 3-150 kHz.

For a few images of S-FSK with EMI, OFDM communication, and EMI from a low energy light: http://navet.swemet.se/files/mfa.htm

jippie
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user17562
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  • For more information similar research, see: http://www.cleen.fi/en/Comms/A%20Novel%20Device%20for%20Real-Time%20Monitoring%20of%20High%20Frequency%20Phenomena%20in%20CENELEC%20PLC%20Band.pdf – user17562 Jan 07 '13 at 13:56