VECTOR MODULATION MODE
3-48
Pulse input selection (applies if Option 002 fitted)
Pressing the
[Pulse Input]
key enables and disables the pulse input. With pulse input enabled,
applying 5 V to the PULSE INPUT connector turns the RF carrier on and 0 V turns the carrier off.
This facility enables the RF output to be rapidly turned on or off.
Sideband and IF selection
The
Vector Modulation Configuration
menu is used to determine which of four IFs is used and
whether the selected carrier frequency corresponds to the upper or lower sideband frequency in the
mixing process. Automatic selection is also available which minimises the effects of any mixing
products resulting from the frequency conversion process.
To select the required sideband, repetitively press the
[U/L/Auto Sideband]
key which cycles
through the selections
UPPER, LOWER
and
AUTO SIDEBAND
as shown by the display. When
AUTO
is selected, the selection is displayed in brackets. Manual settings which are unacceptable
(depending on carrier frequency) are disallowed and an error message is displayed.
To select the required IF, repetitively press the
[IF Freq Select]
key which cycles through the
selections
120 MHz, 132 MHz, 160 MHz, 176 MHz
and
AUTO
IF as shown by the display. When
AUTO
is selected, the automatically chosen optimum IF is additionally displayed in brackets.
Modulation polarity
To change the modulation polarity press the
[Mod. Polarity]
key which toggles between
NORMAL modulation sense and INVERSE modulation sense. INVERSE can be used to
simulate IF signals where the modulation sense has been reversed in frequency converting the
input RF signal (in effect this exchanges the I and Q inputs).
External envelope
Pressing the
[External Envelope]
key toggles between enabling and disabling an external envelope
input connected to the front panel ENVELOPE IN connector. But note that when enabled,
Rayleigh and Rician fading cannot be simulated. The level is linearly controlled with 0 V
producing no output and +1 V producing the set RF output.
Menu exit
Press [SIG GEN] to return to the
Sig Gen
menu where further selections may be made.