Cable Crosstalk Impulse Response Measurements

The University of Ottawa cable

Description of Cable

• This cable is owned by the University of Ottawa.
• This cable is described in the paper:

  A. Fung, L. S. Lee and D. D. Falconer, "A facility for near end crosstalk measurements on ISDN subscriber loops," in Conf. Rec. IEEE Globecom 89, vol. 3, (Dallas, TX, USA), pp. 1592-1596, Nov. 27-30, 1989.

• Cable Specifications:

           Manufactured: November 1976
           2000 ft Tel Cable NE BKTB 50PR 26GA
                                       50 PAIRS , 26 GAUGE
           PIC C-ALP. PAT. 1963
           NORTHERN ELECTRIC
           MADE IN CANADA
  

• number of twisted pairs in cable: 50
• gauge, AWG: 26
• length: 2000 feet
• insulation: PIC

Description of Measurements

• Near-end crosstalk measurements were performed.
• Far-end crosstalk measurements were not performed.
• All the far ends of the cable were terminated with 120 Ohm resistors.
• All the near-ends were connected to hybrid transformers or 120 Ohm resistors.
• An input pulse was put into one hybrid transformer.
• An output pulse was observed at the output of a hybrid transformer.
• The cable impulse response consists of a hybrid transformer, the crosstalk coupling path, and a second hybrid transformer.
• Brent Petersen's opinion about the measurements: The twisted pairs in the cable all have similar geometries. All the crosstalk responses have nearly identical shapes. The energy (or power) of crosstalk impulse responses vary 3 dB over all the 49 pairs.

Description of Files

• Number of files: 52
• File descriptions:
  • pulse - This was the input pulse which was put into the into the hybrid transformer. The file is a collection time samples
    • abscissa: 4e-9 seconds/sample
    • ordinate: 0.08 volts/level, 8-bit linear analog-to-digital conversion, the numbers are in the range 0 to 255.
    • If you use matlab, to plot the pulse, do the following:
      • load pulse
      • plot([0:1023]*4e-9,pulse*0.08)
      • The abscissa is in seconds and the ordinates are in volts.
  • f1_21 - This is the response on twisted-pair number 21 to an input on twisted-pair number 1.
    • abscissa: 1e-8 seconds/sample
    • ordinate: 0.0008 volts/level, 8-bit linear analog-to-digital conversion, the numbers are in the range 0 to 255.
    • If you use matlab, to plot f1_21, do the following:
      • load f1_21
      • plot([0:1023]*1e-8,f1_21*0.0008)
      • The abscissa is in seconds and the ordinates are in volts.
  • f2_21, f3_21, f4_21, ... - These have the same parameters as f1_21.
  • hybrid - This pulse was the output of a hybrid transformer in response to the input pulse.
    • abscissa: 4e-9 seconds/sample
    • ordinate: 0.02 volts/level, 8-bit linear analog-to-digital conversion, the numbers are in the range 0 to 255.
    • If you use matlab, to plot the pulse, do the following:
      • load hybrid
      • plot([0:1023]*4e-9,hybrid*0.02)
      • The abscissa is in seconds and the ordinates are in volts.
  • matrix - Instead of loading all the files described above, you could instead download this single file. Its format is as follows. The data in the individual files shown above is in column format, whereas the data in the matrix file is in row format. The meaning of the rows is as follows:
    • row 1 - pulse
    • row 2 - f1_21
    • row 3 - f2_21
    • row 4 - f3_21
    • ...
    • row 21 - f20_21, except the last 194 samples at the end of the row are -1. These values of -1 should be discarded. The problem is that for this file, only 830 samples were collected, unlike the other files which have 1024.
    • row 22 - f22_21
    • row 23 - f23_21
    • row 24 - f24_21
    • ...
    • row 50 - f50_21
    • row 51 - hybrid