Chapter 4 69
Making SRL Measurements
How to Make SRL Measurements
Perform the SRL Cable Scan
Once the connector model has been established for the best response, the cable
should be scanned at narrow frequency resolution to look for narrow response
spikes that are characteristic of periodic defects in the cable. The SRL cable scan is
required to determine the cable's SRL with 125 kHz resolution.
By taking five sweeps of 1601 points each at slightly different frequency ranges (see
Table 4-3), the analyzer can obtain 8005 distinct frequency points to achieve the
desired frequency resolution of 125 kHz.
The resolution of the SRL measurement is determined by the following formula:
where N is the number of measurement points. See the table below.
Table 4-3 SRL Cable Scan Frequency Sweeps
Resolution
Fstop Fstart–
N
--------------------------------
=
F
start
F
stop
N Resolution
No Cable Scan 5 MHz 1000 MHz 201 4.95 MHz
5 MHz 1000 MHz 1601 612 kHz
Using Cable Scan 5 MHz 1000 MHz 8005 125 kHz
Sweep
Number
Start Frequency (MHz) Stop Frequency (MHz)
1 5.000 999.500
2 5.125 999.625
3 5.250 999.750
4 5.375 999.875
5 5.500 1000.000
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