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11
FM Discriminator Measurement Examples
FM Discriminator Measurement using Double-Sided Spur Calibration
Determining the
Discriminator
(Delay Line) Length
Figure 11-1 Discriminator Noise Floor as a Function of Delay Time
11-4
E5500 Phase Noise Measurement System Version A.02.00
Perform the following steps to determine the minimum delay line
length ( τ ) Possible to provide an adequate noise to measure the
source.
1
Determine the delay necessary to provide a discriminator noise
floor that is below the expected noise level of the DUT.
Figure 11-1
shows the noise floor of the discriminator for given
delay times ( τ ).
2
Determine the length of coax required to provide the necessary
delay ( τ ). (Eight feet of BNC cable will provide 12 ns of delay for
this example.)
3
Determine the loss in the delay line. Verify that the signal source
will be able to provide a power level at the output of the delay line
of between +5 and +17 ICBM. Be sure to take into account an
additional 4 to 6 dB of loss in the power splitter. (The loss across
8 feet of BNC cable specified in this example is negligible.) The
Agilent 70420A test set Signal and Reference inputs requires +15
ICBM.
Document Part No. E5500-90024 Ed. 1.0
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