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DSL lines diagnostics

DSL lines diagnostics. - Parameters of analog part of xDSL transceiver. Access Networks 20 10/11 Ľ. Maceková, KEMT- FEI – TU - Košice. Describing of DMT in time domain (DMT is transport method in ADSL and VDSL systems):. U k ... amplit ude of k-t h carrier ( it is modulated by QAM)

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DSL lines diagnostics

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  1. DSL lines diagnostics - Parameters of analog part of xDSL transceiver Access Networks 2010/11 Ľ. Maceková, KEMT- FEI – TU - Košice

  2. ... Describing of DMT in time domain (DMT is transport method in ADSL and VDSL systems): Uk ... amplitudeof k-thcarrier (it is modulated by QAM) φk ... phase of k-thcarrier ω0 = 2π. 4312,5 s-1 ... angle speed limiting areas Fig.Typical time domain DMT signal look with limiting areas (signal mustn’t exceed their boundaries)

  3. Actually, we evaluate nonlinear distortion, which is integrated in parameters : THD… Total Harmonic Distortion IMD… Inter-Modulation Distortion SINAD… SNR plus Distortion THD + N ... THD plus Noise SFDR… Spurious Free Dynamic Range In addition, in DMT signal area: MTPR ... Multi-Tone Power Ratio SNR ... Signal-to-Noise Ratio… we know this already - all parametersare in units [dB](logarithmicarea) or clear number (ratio)or in [%]

  4. THD … Total Harmonic Distortion P1; f P1, P2, P3, ... input output power of basic frequency signal power of higher harmonics; result of devices nonlinearities (because of nonlinear transfer characteristics of amplifiers) We measure all higher harmonics which can be distinguished from noise

  5. IMD … Inter-Modulation Distortion • it is product of nonlinearities of transfer characteristics when actuated by two frequencies signal • it is sum of intermodulation products of 2 input harmonics (sums, differencies and multiples) f1,f2,; f2>f1 f2±f1, f2 ±2f1,f2 ±3f1,... input output - the measurement: by modulation method or by differencial method[1]

  6. SINAD – SNR plus Distortion • parameter which contains the noise and nonlinear distortion Psig in Psig, P2, P3, ..., noise distortion total output signal power output signal after filtration of input signal

  7. SFDR – Spurious Free Dynamic Range • it is about nonlinear properties of devices again • they measure partial harmonic elements and another distortion elements; we are interested in distortion element with highest amplitude power of the distortion element with highest amplitude (hence SFDR < 0 dB) power of basic signal (1-st harmonic frequency) (measurement signal) [1]

  8. MTPR… Multi – Tone Power Ratio • this parameter is established for DMT average subchannel power (applied; transmitted) max. power of distortion signal in the position of unused subchannel (‘empty bin’) [1], [2]

  9. … and another measurements: • measurementof impulse noise robustness • measurement of ADSL splitters • measurement of influensis of ADSL in voice (telephone) band • etc.

  10. References: [1] J. Vodrážka, M. Havlan: Přístupové přenosové systémy, Cvičení – Měření na přípojkách xDSL, ČVUT Praha, 2003. [2] http://www.analog.com/static/imported-files/tutorials/MT-053.pdf

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