User`s guide

110 Agilent E5505A User’s Guide
5 Absolute Measurement Fundamentals
What Sets the Measurement Noise Floor?
The noise floor for your measurement is set by two things:
• The noise floor of the phase detector and low-noise amplifier (LNA)
• The noise level of the reference source you are using
The System Noise Floor
The noise floor of the system is directly related to the amplitude of the input
signal at the R input port of the system’s phase detector. Table 11 shows the
amplitude ranges for the L and R ports.
If the L port (Reference Input) signal is within the amplitude range shown in
Table 11, the signal level at the R (Signal Input) port sets the noise floor for the
system.
Figure 73 shows the relationship between the R (signal) input level and the
system noise floor.
Table 11 Amplitude ranges for L and R ports
Phase Detector
50 kHz to 1.6 GHz 1.2 to 26.5 GHz
1
50 kHz to 26.5 GHz
2
Ref Input
(L Port)
Signal Input
(R Port)
Ref Input
(L Port)
Signal Input
(R Port)
AM Noise
+ 15 dBm
to
+ 23 dBM
0 dBm
to
+ 23 dBM
+ 7 dBm
to
+ 10 dBM
0 dBm
to
+ 5 dBM
0 dBm
to
20 dBM
1 Phase noise test set Options 001 and 201 with no attenuation.
2 Phase noise test set Option 001 with no attenuation.