
3 Approximate Sensitivity of Delay Line Discriminator
.01 .1 1 10 100 1K 10K 100K 1M 10M 40M
X(f) [dBc/Hz] vs. f [Hz]
Description
The dependence of a frequency discriminator's sensitivity on the offset
frequency is obvious from this graph. By comparing the sensitivity
specified for the phase detector of the HP 3048A to the delay line
sensitivity, it is apparent the delay line sensitivity is "tipped up" by
20 dB/decade beginning at an offset of ^f- The sensitivity graphs indicate
the delay line frequency discriminator can be used to measure some
types of sources with useful sensitivity. Longer delay lines will improve
the 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. (Refer to Calibr Process in Chapter 2, Measurement Definitions,
for delay line restrictions.)
7-10 Quick Reference
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