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Amplitude Noise Measurement
The level of amplitude modulation sidebands is also constant with increasing
modulation frequency. The AM detector gain can thus be measured at a single
offset frequency and the same constant will apply at all offset frequencies.
Replacing the phase detector with an AM detector, the AM noise measurement
can be calibrated in the same way as PM noise measurement, except the phase
modulation must be replaced with amplitude modulation.
The AM noise measurement is a characterization of a source. The residual AM
noise of a DUT can only be made by using a source with lower AM noise, then
subtracting that AM noise from the measured output noise of the DUT. The
noise floor of this technique is the noise floor of the source.
AM noise measurement block diagrams
E5505a_noise_sys_block_n5505a_opt001
01 Mar 04 rev 1
Figure 217 AM noise system with N5500A opt 001
DUT
E5505a_noise_sys_block
01 Mar 04 rev 1
Figure 218 AM noise system with external detector
Agilent E5505A User's Guide
DUT
AM detector
AM Noise Measurement Fundamentals
Test set
Signal
input
Test set
Noise
input
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