User`s guide

Agilent Technologies E5500 Phase Noise Measurement System 11-19
FM Discriminator Measurement Examples
Discriminator Measurement using FM Rate and Deviation Calibration
Determining the
Discriminator
(Delay Line) Length
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 dBm. 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/HP 70420A test set Signal
and Reference inputs requires +15 dBm.
Figure 11-4 Discriminator Noise Floor as a Function of Delay Time