Metrix GX1010 Notice De Fonctionnement page 145

6.5.2.1. Simplified Generator Block Diagram
The diagram shows the simplified paths for the main and auxiliary outputs. LF and HF refer
to the Low Frequency and High Frequency modes set for Squarewave/pulses and Auxiliary
output in the SQWAVE GEN= and AUX= fields of the Options menu, see Waveform
Generation Options section. When these fields are set to AUTO the modes automatically
change from LF to HF above 30kHz; setting to LF or HF will set that generating mode
whatever the generator frequency.
Similarly, when set to AUTO on the Options menu, the Filter will be switched in or out
depending on waveform as shown; setting Filter ON or OFF will override this and all or
none of the waveforms will be filtered.
6.5.2.2. Interaction of Various Option Settings
The more important points to consider when setting the Option menu fields to other than
AUTO are as follows:
• The comparator which generates MAIN HF squarewaves/pulses is driven, by default, by
a filtered sinewave. If the filter is set OFF, the waveform driving the comparator will be
poorer and the HF squarewave, etc. will be degraded.
• HF AUX out is generated from the same comparator; the waveform driving the
comparator depends on the MAIN waveform selection. For HF squarewave/pulse MAIN
outputs the driving waveform is a filtered sinewave as described above; for sinewave
and triangle main outputs the comparator drive is the waveform itself (also filtered). The
main waveform also drives the comparator for ramp, staircase and arbitrary waveforms
plus LF squarewave/ pulses, all of which are unfiltered; this means that if the MAIN
waveform shows edge jitter as the frequency increases, so will the HF AUX out. For this
reason, the default (AUTO) setting for AUX out is LF mode at all frequencies for main
waveforms of ramp, staircase, arbitrary and LF squarewaves/pulses.
• By default, ramp, staircase, arbitrary and all waveforms whose symmetry is set to
other than 50% are unfiltered. It may be desirable to force the filter ON under some
circumstances to improve waveform quality, e.g. for higher frequency sinewaves that
are only slightly asymmetric.
• Similarly asymmetric HF squarewaves/pulses and AUX outputs generated from the
comparator will be improved if the filter is forced ON to filter the signal driving the
comparator.
• when staircase, arbitrary or LF mode squarewaves/pulses are selected the comparator
is driven by the unfiltered main waveform. With all except squarewaves it is possible to
have a waveshape which never crosses the comparator threshold, thus HF AUX output
may be permanently high or low. To avoid this situation, the default (AUTO) AUX setting
is LF mode; however, in this mode edge jitter will become increasingly significant at
higher frequencies.
58 - II GX1010