Types Of Modulation; Fsk Frequency Shift Keying; Psk Phase Shift Keying - Hameg Instruments Hm8131-2 Handbuch

will show the selection of "Start", "Stop", "Time" and
"Lin/Log". Return to the "Sweep" menu is via the
"Prev." key. If the sweep mode is selected via the menu
mode, it is possible to adjust all parameters prior to
starting the sweep. The activation of the sweep follows
upon parameter selection by pressing the SWP key [8].
If the start frequency has a lower value then the stop
frequency the sweep "direction" is from the lower to
the higher frequency. If the start frequency is higher
than the stop frequency the sweep "direction" is inver-
se. It starts from the higher and "steps" to the lower
frequency. The sweep time is adjustable between 0.01s
to 40s. In addition a linear or logarithmic sweep
characteristic can be selected.
Figure 3: Swept output signal; Ramp output
The frequency range from 0.1 Hz to the highest frequency
can be covered in one sweep. The ramp output on the
BNC connector "Sweep out" corresponds to the
frequency of the sweep. The corresponding output
voltage is from 0 to 5 V. The signal can be used to trigger
an oscilloscope or to control a plotter.
Whenever the sweep is activated, direct return
from the sweep menu to the main menu is not
possible. Therefore the required signal function
should be selected before the sweep is activated.
Amplitude and offset are selectable as during the
normal operation. However, these functions must
be canceled in order to return to the sweep menu.
To quit the sweep menu simply press the SWP [12]
key.
The sweep mode can also be triggered. This is possible
via the mode-menu. As soon as the trigger mode for the
sweep is activated, the pre-selected signal form is
generated, but the sweep is still in Stand-by for the trigger
signal. When triggered the start of the sweep is the same
as in the normal trigger mode. The sweep will follow the
pre-selected parameters. Subsequently, the instrument
will wait for another trigger signal.

Types of Modulation

The HM8131-2 provides FSK, PSK and AM. The modulation
types are selected via the menu "OPTIONS MENU 2".
Subject to change without notice
AM
AM can be set with a modulation depth from 0 - 100 % in
1 % steps. The signal source can be external or internal.
The internal modulation source is 1,000 Hz sinewave. The
external modulation source is connected at the rear of
the instrument to the input labeled "AM INP" [19]. The
external modulation source can be any signal type. The
indication of the modulation depth is only correct when
the external signal is 1 kHz with an amplitude of 1 V RMS.
The function is activated via the menu keys AMint or
AMext. An arrow in the display in front of the selected
modulation type indicates the activated function. The
function is canceled by pressing the menu key again.

FSK Frequency Shift Keying

The Frequency Shift Keying (FSK) modulation generates a
signal which changes between two preset frequencies,
the carrier " F0" and the hop " F1" frequency. The rate at
which the output shifts between the two frequencies is
determined by the signal which is connected to front-panel
trigger terminal [2]. The carrier and the hop signal can be
adjusted independently in frequency. The function is
activated by the menu key "On" and canceled by the key
"Off".
The HM8131-2 can produce FSK waveforms using sine,
square, triangle, ramp, and arbitrary waveforms.
Whenever the modulation type FSK is active, the menu
"FSK" can not be canceled. Consequently, the desired
signal function should be selected prior to the FSK
function. The FSK modulation must be canceled by
pressing the Off-key in the menu to return to the main
menu.

PSK Phase Shift Keying

The Phase Shift Keying (PSK) modulation generates a
signal which changes its phase relation between two
preset phase angles. The value can be adjusted from 0
degrees to 359.9 degrees for the two phase values.
The set phase angle is not depending from the signal
output at the trigger connector at the rear of the HM8131-
2.
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