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FM Discriminator Measurement using Double-Sided Spur Calibration
To prevent damage to the test set's components, do not apply the input signal to the
C A UTI ON
signal input connector until the input attenuator (N5500A Option 001) has been
correctly set for the desired configuration, as shown in
signal when the connection diagram appears.
Required
Table 40
noise test system and your DUT.
Equipment
To ensure accurate measurements allow the DUT and measurement equipment to warm up
NO T E
at least 30 minutes before making the noise measurement.
Table 40 Required Equipment for the FM Discriminator Measurement Example
Equipment
Signal Generator
Power Splitter
Delay Line
Phase Shifter
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
2
3
Agilent E5505A User's Guide
shows equipment required for this example in addition to the phase
Determine the delay necessary to provide a discriminator noise floor that is
below the expected noise level of the DUT.
the noise floor of the discriminator for given delay times (τ).
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.)
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 test set Signal and Reference inputs requires +15
ICBM.
FM Discriminator Measurement Examples
Quantity
Comments
1
+19 dBm output level at tested carrier frequency.
Calibrated FM at a 20 kHz rate with 10 kHz Peak
Deviation.
1
NARDA 30183
Delay (or length) adequate to decorrelate source
noise.
±
°
1
180
phase shifter at lowest carrier frequency
tested.
Figure 181
Table
41. Apply the input
on page 252 shows
10
251
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