Hameg HM5012 Manual page 37

tuning since both are effectively tuned by the same VTO. This
precision tracking exists in all analyzer scan modes. Thus, in full
scan, the tracking generator output is a start-stop sweep, in zero
scan the output is simply a CW signal.
The tracking generator signal is generated by synthesizing and
mixing two oscillators. One oscillator is part of the tracking
generator itself, the other oscillator is the spectrum analyzer's
1st LO. The spectrum analyzer/tracking generator system is used
in two configurations: open-loop and closed-loop. In the open-
loop configuration, unknown external signals are connected to
the spectrum analyzer input and the tracking generator output
is connected to a counter. This configuration is used for making
selective and sensitive precise measurement of frequency, by
tuning to the signal and switching to zero scan.
In the closed-loop configuration, the tracking generator signal is
fed into the device under test and the output of the device under
test is connected to the analyzer input.
In this configuration, the spectrum analyzer/tracking generator
becomes a self-contained, complete (source, detector, and
display) swept frequency measurement system. An internal
leveling loop in the tracking generator ensures a leveled output
over the entire frequency range. The specific swept measure-
ments that can be made with this system are frequency response
(amplitude vs. frequency), magnitude only reflection coefficient,
and return loss. From return loss or reflection coefficient, the
SWR can be calculated. Swept phase and group delay
measurements cannot be made with this system; however, it
does make some unique contributions not made by other swept
systems, such as a sweeper/network analyzer, a sweeper/
spectrum analyzer, or a sweeper/detector oscilloscope.
Precision tracking means at every instant of time the generator
fundamental frequency is in the center of the analyzer passband,
and all generator harmonics, whether they are generated in the
analyzer or are produced in the tracking generator itself, are outside
the analyzer passband. Thus only the tracking generator funda-
mental frequency is displayed on the analyzer's CRT. Second and
third order harmonics and intermodulation products are clearly
out of the analyzer tuning and, therefore, they are not seen. Thus,
while these distortion products may exist in the measurement
set-up, they are completely eliminated from the CRT display.
Subject to change without notice
37