Amplitude Modulation; Amplitude Modulation (Internal) - Metrix GX1010 Notice De Fonctionnement

arbitrary; there will be an instantaneous transition from/to the DC Offset level to/from the
current waveform phase at the start/stop of the gating period.
With the source set to EXTernal, the generator waveform is gated on whilst the external
signal applied to the EXT TRIG input exceeds the gate threshold (1·5V), see External
Trigger Input section.
With the source set to MAN/REMOTE, the generator waveform is gated on and off with
alternate presses of the MAN/SYNC key or by the appropriate commands via the RS232 or
GPIB interfaces.
With the source set to TGEN, the generator waveform is gated on as explained in the
Internal Trigger Generator section; the trigger generator is set exactly as described in the
Trigger Source section.
4.5.

Amplitude Modulation

Two modes of operation are available from the AM menu:
• Amplitude Modulation using the Internal Trigger Generator as the modulation source in
which the modulation depth is expressed as a percentage and constant modulation
depth is maintained as the main generator (carrier) amplitude is varied.
• VCA (Voltage Controlled Amplitude) mode, in which the main generator amplitude is
directly proportional to the external modulating signal voltage applied to the rear panel
VCA IN socket. Suppressed carrier modulation (SCM) is achievable in this mode.
AM mode is turned on and off with alternate presses of the AM key; the lamp beside the
key lights when AM mode is on. The AM parameters are all set from the AM edit menu
which is selected by pressing the blue EDIT key followed by the AM key. When AM edit is
selected the lamp beside the AM key flashes to show edit mode regardless of whether AM
mode is currently selected to be on or off.

4.5.1. Amplitude Modulation (Internal)

With the edit cursor in the SOURCE field of the AM edit menu the DIGIT keys or rotary
control can be used to toggle the source between EXT VCA and TGEN (Trigger Generator)
i.e. between external VCA mode and internal AM mode.
4.5.1.1. Modulation Frequency
Select TGEN in the SOURCE field and move the cursor to the TGEN field to set the period
of the Internal Trigger Generator, the modulation source for internal AM. The internal
trigger generator produces a squarewave with a period that can be set from 0·02ms
(50kHz) to 200s (·005Hz). Period entries that cannot be exactly set are accepted and
rounded up to the nearest available value, e.g. ·109ms is rounded to ·12ms. The generator
output is available as a TTL level signal at the rear panel TRIG/SWEEP OUT socket.
Beside the generator period value the equivalent frequency is shown; this is for information
only and is not an editable field. Because the internal trigger generator can be used by the
trigger, gate, FSK and AM functions, and can be set from their respective menus, an
information field is displayed in brackets beside TGEN when this is selected as the source.
This field will show [FREE] when TGEN is not used elsewhere, or any of the letters [G, F,
A, T] to indicate the generator is currently set as the source on the GATE, FSK, AM, or
TRIG menus respectively, in addition to the menu currently displayed.
GX1010
SOURCE=EXT VCA
TGEN=1·00ms 1·000kHz
INT MOD DEPTH=030%
INT MOD=SQUARE
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