Extended Operating Modes; Fig. 5.2: Sine Wave With Amplitude Modulation; Fig. 5.1: Key's For Additional Functions; Sweep Mode (Sweep) - Hameg HMF2550 Handbuch

5 Extended operating modes

5.1 Available modulation
types (MOD)
A modulated signal consists of
a carrier signal and a superim-
posed modulation signal. The
HMF2525 / HMF2550 offers the
following types of modulation:
AM (amplitude modulation),
FM (frequency modulation), PM
(phase modulation), PWM (pulse
width modulation), and FSK (frequency shift keying). The type
of modulation is selected by pushing the MOD key and choo-
sing it in the soft key menu TYPE via the knob. Only one type of
modulation may be active at any time.
With AM the amplitude of the carrier signal will be changed
by the amplitude of the modulating signal. After selecting AM
in the soft key menu TYPE the modulation depth can be set
from 0 to 100 % in 0.1 % increments (AM DEPTH). Internal or
external modulation can be chosen. When external modu-
lation was selected, the carrier will be modulated with this
external signal.

Fig. 5.2: Sine wave with amplitude modulation

External modulation signals are connected to the rear panel
connector MODULATION INPUT
With FM the frequency of the carrier signal will be varied ac-
cording to the instantaneous value of the modulating signal,
the amplitude remains unaffected.
With phase modulation the phase of the carrier signal will be shifted
according to the instantaneous value of the modulating signal.
The so called pulse width modulation (PWM) is
only available with the pulse waveform; it will be
automatically chosen when the waveform „pulse"
is selected.
The soft key menu item SHAPE offers the following modulation
waveforms, available for the modulation types AM, FM, PM,
and PWM:
– Sine Function
– Square Function
– Positive / Negative Ramp Function
Fig. 5.1: Key's for
additional functions
.
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E x t e n d e d o p e r a t i n g m o d e s
– Triangle Function
– White Noise Function
– Pink Noise Function
– Cardinal Sine
– exponential rise / fall
The selected function will be indicated in the lower menu field.
The values of the parameters are set using the numerical key-
board or the knob . Additionally, user defined arbitrary
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signals can be load.
The modulation type frequency shift keying (FSK) generates a
signal which alternates between two predefined frequencies:
the carrier and the hop frequency. The alternation will depend
on the FSK rate set in the internal source mode or on the signal
at the trigger input TRIG INPUT in the external source mode.
Both carrier and hop frequencies may be set entirely indepen-
dent of each other. The setting of the individual parameters is
performed via the numerical keyboard or the knob.
The modulation type FSK only performs in combi-
nation with a TTL signal at the TRIG INPUT socket.
5.2

Sweep mode (SWEEP)

In the sweep mode the start frequency will be increased in
steps within a given sweep time (SWEEP time) up to a preset
stop frequency. In case the stop frequency was chosen higher
than the start frequency the sweep will run from the higher to
the lower frequency. The center frequency and the span are
directly related to the start and stop frequencies. Additionally,
linear or exponential sweep can be chosen. The socalled marker
frequency must be set between the start and stop frequencies.
If the signal frequency reaches the marker frequency a signal
will be generated available at the TRIG OUTPUT connector.
The sweep function can not be combined with the
gating function.
The sweep mode is selected by pushing the SWEEP key which
will light up. The parameters sweep time, start and stop fre-
quency can be set independently.
The sweep parameters are set via the numerical keyboard, the
knob or the arrow keys. Setting or changing of parameters are
also possible during a sweep, any changes will be immediately
apparent. The sweep actually running will be terminated and a
new one started; the display will show the parameters activated.
The sweep function will be left by pushing the
SWEEP key again.
The sweep time is selectable from 1ms to 500s. A sweep signal
may also be triggered, this can be selected with the soft keys.
In trigger mode the HMF2525 / HMF2550 will generate the start
frequency and wait for the trigger in order to start a sweep. The
sweep will run with the parameters selected and stop, waiting
for the next trigger.
5.2.1 Submenu TRIGGER
In this menu the trigger source (internal / external), the con-
nector TRIG OUTPUT (On/Off) as well as the associated edge
settings (rising / falling) can be defined.
The trigger source can be set to intern (immediately) or extern.
In the mode EXTERNAL 3 different trigger options exists. The
instrument selects / performs the appropriate function auto-
matically:
Subject to change without notice
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