User`s guide

366 Agilent E5505A User’s Guide
16 Reference Graphs and Tables
Approximate Sensitivity of Delay Line Discriminator
The dependence of a frequency discriminator's sensitivity on the offset
frequency is obvious in the graph in Figure 292. By comparing the sensitivity
specified for the phase detector to the delay line sensitivity, it is apparent the
delay line sensitivity is “tipped up” by 20 dB/decade beginning at an offset of
1/2πτ. The sensitivity graphs indicate the delay line frequency discriminator
can be used to measure some types of sources with useful sensitivity. Longer
delay lines improve sensitivity, but eventually the loss in the delay line will
exceed the available power of the source and cancel any further improvement.
Also, longer delay lines limit the maximum offset frequency that can be
measured.
Figure 292 Delay line discriminator sensitivity
10M100M100101.1.01 1M100K10K1K
-180
0
20
40
-20
-40
-60
-80
-100
-120
-140
-160
E5505a_delay_line_discr
02 Mar 04 rev 1
10nS
100nS
1μS
L( f ) = -[dBc/Hz] vs. f [Hz]
YIG
8642B sig gen
DRO
10 MHz XTAL
100 MHz XTAL
SPEC
Typical