MOGlabs ARF021, Manual

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6.3 Dual modulation with PID
37
6.3 Dual modulation with PID
It is possible to perform PID simultaneously with another form of
modulation enabled. For example, PID can be used to compensate
for the frequency response of
RF
components or the
AOM
when per-
forming wide-band frequency modulation, as shown in Listing 6.1.
# enable FM on channel 1
MDN,1,FREQ,ON
GAIN,1,FREQ,0x3FFFF
# set PID gains and enable
PID,GAIN,1,P,0.1
PID,GAIN,1,I,0.01
PID,GAIN,1,D,0
PID,ENABLE,1,AMPL
# set FM to SLOW mode, allowing PID to be FAST
FMSPEED,1,SLOW
Listing 6.1:
Simultaneous FM and PID intensity stabilisation example.
Limitations of the DDS interface mean that only one of PID and
external modulation can be performed at full bandwidth (
§
5.3). Most
applications will benefit from using PID in “fast” mode, but some
applications such as compensating for thermal drift in AOM diffraction
efficiency do not require high bandwidth and can be operated in
“slow” mode.