Agilent Technologies E1420B, Руководство пользователя

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268 Agilent E5505A User’s Guide
10
FM Discriminator Measurement Examples
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 199 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 b5
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 re15
ICBM.
.
Defining the measurement
1 From the File menu, choose Open .
2 If necessary, choose the drive or directory where the file you want is stored.
3 In the File Name box, choose “ vco_r&d.pnm. ” See Figure 200 .
Figure 199 Discriminator noise floor as a function of delay time
10M 100M 100 10 1 .1 .01 1M 100K 10K 1K
-180
0
20
40
-20
-40
-60
-80
-100
-120
-140
-160
E5505a_disc_noise_floor
01 Mar 04 rev 1
10nS
100nS
1
µ
S
L
(
f
) =
-
[dBc/Hz] vs.
f
[Hz]