User`s guide

FM Discriminator Measurement Examples 10
Agilent E5505A User’s Guide 269
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 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.
.
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 100M100101.1.01 1M100K10K1K
-180
0
20
40
-20
-40
-60
-80
-100
-120
-140
-160
E5505a_disc_noise_floor
01 Mar 04 rev 1
10nS
100nS
1μS
L( f ) = -[dBc/Hz] vs. f [Hz]