Chapter 12 12-19
Theory of Operation
Source Theory Overview
Source Operation in other Modes and Features
Besides the normal network analyzer mode, the analyzer has extra modes and features to
make additional types of measurements. The following describes the key differences in
how the analyzer operates to achieve these new measurements.
Frequency Offset
The analyzer can measure frequency-translating devices with the frequency offset feature.
The receiver operates normally. However, the source is pretuned to a different frequency
by an offset entered by the user. The device under test will translate this frequency back to
the frequency the receiver expects. Otherwise, phase locking and source operation occur as
usual.
Harmonic Analysis (Option 002)
The analyzer can measure the 2nd or 3rd harmonic of the fundamental source frequency,
on a swept or CW basis, with the harmonic analysis feature (optional).
To make this measurement, the reference frequency (normally 1 MHz) from the A12
reference assembly to the A11 phase lock assembly is divided by 1, 2, or 3. See Figure 12-6.
The fractional-N assemblies are also tuned so that the correct harmonic (comb tooth) of the
1st LO is 0.500 or 0.333 MHz below the source frequency instead of the usual 1.000 MHz.
The analyzer pretunes the A3 source normally, then phase locks the 1st IF to the new
reference frequency to sweep the fundamental source frequency in the usual way. The key
difference is that the 1st IF (output from the R sampler) due to the fundamental and used
for phase locking is now 0.500 or 0.333 MHz instead of 1.000 MHz.
Table 12-3 High Band Subsweep Frequencies
Fractional-N (MHz) Harmonic Source Output
(MHz)
30 to 60 1/2 16 to 31
30 to 60 1 31 to 61
30 to 60 2 61 to 121
40 to 59 3 121 to 178
35.4 to 59.2 5 178 to 296
32.8 to 59.4 9 296 to 536
35.7 to 59.5 15 536 to 893
33.0 to 59.5 27 893 to 1607
31.5 to 58.8 51 1607 to 3000
Option 006
37.0 to 59.6 83 3000 to 4950
49.0 to 59.4 101 4950 to 6000
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