PeakTech 4055 Handbuch Seite 26

4.4. Frequency sweeping
In frequency sweep, the output frequency changes from the start frequency point to the end frequency point
according to the setting sweep time. Users may sweep within the whole frequency range. During this
process, the phase of output signals is continuous. All the 16 kinds of waveform could be swept, of course it
makes no sense to sweep DC or noise. Linearity frequency sweeping is similar with ramp frequency
modulation, with the difference of, frequency sweeping does not use modulation waveform, but continuously
output a series of discrete frequency points according to certain time interval.
Press【Sweep】key, the light of it will be lighted and the generator enters frequency sweeping function.
4.4.1 Start and end frequency
* Press【Menu】key and "Start" letter and then set start frequency point.
* Press【Menu】key to light "Stop" letter and then set end frequency point.
* If the end frequency value is more than the start frequency value, the sweep is positive from lower
frequency to higher frequency, increasing step by step from the start frequency to the end frequency and
then return to the start frequency.
* If end frequency value is less than the start frequency value, the sweep is opposite from higher frequency
to lower frequency, decreasing step by step from the start frequency to the end frequency and then return
to the start frequency.
4.4.2 Sweeping time
* Press【Menu】-key and then set sweep time value.
* Sweep time means the time of sweeping from the start frequency point to the end frequency point. * The
sweep time of every frequency point is the same, so the longer the sweep time is, the more frequency
points are swept, the less the step of the frequency point is, and the finer the sweep is.
* The shorter of the sweep time is, the less frequency points are swept, the more the step of the frequency
point is, and the rougher the sweep is.
4.4.3 Sweeping mode
* Press【Menu】-key and then set sweeping mode. Set the value as 0, the character "linear" will be
lighted, and the sweeping mode now is linearity. Set the value as 1, the character "log" will be lighted, to
select logarithm mode.
* Under linearity sweeping mode, the frequency step is fixed, but a fixed frequency step always does a bad
effect when sweeping comparatively wide-range frequency.
* In that case, the resolution is high when sweeping high end of frequency, the frequency changes slowly,
and the sweeping is fine.
* But the resolution is low when sweeping the low end of frequency, the frequency changes very quickly,
the sweeping is rough. *
* So linearity sweeping is applicable only for sweeping with narrow frequency range.
* Under logarithm sweeping mode, the frequency step value is not fixed but changes according to logarithm
relation.
* When sweeping the high end of frequency, the frequency step value is comparatively large; when
sweeping the low end of frequency, the frequency step value is comparatively small.
* The frequency change is comparatively average for sweeping with wide frequency range.
* So logarithm sweeping is applicable for sweeping with wide frequency range.
4.4.4 Sync output
* During frequency sweeping, the "Sync" port on the front panel output a sync signal.
* A sync signal is a pulse wave signal with TTL level, of which the rising edge of the pulse is match along
with the start point of the sweeping, and the falling edge is match along with the middle point of the
sweeping area, the period of the pulse wave is the same with sweeping time.
* Press【Freq】,【Period】,【Ampl】or 【offset】key to return back to single frequency function.
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