Amplitude Modulation - HP 8360 B Series User Manual

Amplitude
Modulation
M-14 Operating and Programming Reference
Amplitude modulation can be accepted from an external source at
the AM connector or can be internally generated by swept signal
generators with Option 002. The damage level of the AM input is
A jumper on the A10 ALC board allows you to change the input
impedance to 2 kR (See "Adjustments" in the
Swept Signal Generator/HP 8360 L-Series Swept CW Generator
Service Guide.)
The AM can be scaled either linearly at 100% per
volt or exponentially at 10 dB per volt.
When internal AM is chosen (Option 002), the rate and depth are set
by softkeys in the AM menu. The waveform menu provides a choice
of sine, square, triangle, ramp, or noise waveforms. The monitor
menu lets you output the internally generated modulation waveforms
to the rear panel AM/FM OUTPUT connector. The AM output is
scaled the same as it is generated, either 100%/V or 10 dB/V. This
connector can drive 50 R or greater. The monitor menu also lets you
display the value of the AM depth.
UNLVLED Message
The maximum leveled output is limited by the swept signal
generator's maximum leveled output power specification. (Individual
swept signal generators may be capable of greater leveled output
power; the unleveled message indicates the actual limit.) Amplitude
modulation adds to and subtracts from the reference RF power level.
If an message appears on the display, you may be trying
to modulate beyond the swept signal generator's maximum output
power capability.
OVRMOD Message
The maximum AM depth is limited to approximately 90% by the
detector's ability to sense low power levels. If you try to amplitude
without
modulate too deep
you will see an I:I'GF!MOD message displayed on the message line. Also,
if you modulate below -20 dBm ALC level without using deep AM
mode or below -50 dBm with deep AM or search ALC mode, you
will see an O'4RtKlLS message.
Dynamic Range
The ALC and attenuator combination (when an optional attenuator
is present) are automatically set by the swept signal generator to
keep the ALC in its most accurate range (0 to -10 dBm). This is
coupled attenuator
called the
For applications where modulating across an attenuation switch point
is undesirable, you can uncouple the attenuator and manually set the
power level of the ALC and the attenuator.
For example, setting the power level to 0 dBm in coupled mode will
give an ALC level of 0 dBm and 0 dB of attenuation. In uncoupled
mode, the attenuator can be set to 10 dB and the ALC to +lO dBm,
HP 8360 B-Series
using deep AM mode (explained later),
operating mode.