18-6
Agilent Technologies E5500 Phase Noise Measurement System
Reference Graphs and Tables
Approximate Sensitivity of Delay Line Discriminator
Approximate Sensitivity of Delay Line
Discriminator
The dependence of a frequency discriminator's sensitivity on the offset
frequency is obvious in the graph shown above. 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 1/2
πτ
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.
