AS3909 데이터 시트보기 (PDF) - austriamicrosystems AG
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AS3909 Datasheet PDF : 77 Pages
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AS3909/AS3910 – 62
Application Information
6. When the measured level is equal or lower than the
target level, actual state of the Calibrate Register is
copied in the Modulation Depth Display Register (#11).
Content of this register is used to define the AM
modulated level.
Note(s):After this calibration procedure is finished, the content
of Antenna driver non-modulated level definition register (#13)
should not be changed. Modification of this register content
will change the non-modulated amplitude and therefore the
ration be-tween the modulated and non-modulated level will
be changed.
Please also note that in case the Calibration of antenna resonant
frequency in implemented command Calibrate Antenna has to
be run before AM modulation depth adjustment.
AM Modulation Depth Definition Using Antenna
Driver AM Modulated Level Definition Register (#12)
When the bit 7 (am_s) of the Modulation Depth Definition
Register (#10) is set to 1 the AM modulated level is controlled
by writing the Antenna Driver AM Modulated Level Definition
Register (#12). In case setting of the modulated level is already
known it is not necessary to run the calibration procedure, the
modulated level can simply be defined by writing this register.
There is also a possibility to run a calibration procedure from
externally using the Antenna driver non-modulated level
definition register (#13) and the direct command Measure RF.
The procedure is the following:
1. Write the non-modulated level in register #13 (usually
it is all 0 to have the lower possible output resistance)
2. Switch on the transmitter
3. After the settling time (10μs should be enough), send
the direct command Measure RF. Read result from the
A/D Converter Output Register (#0E)
4. Calculate the target modulated level from the target
modulation index and result from the previous point
5. In the following iterations content of the register #13 is
modified, the command Measure RF performed and
result compared to the target modulated level as long
as the result is not equal or close enough to the target
modulated level.
6. At the end the content of the register #13 which results
in the target modulated level is written in the Antenna
Driver AM Modulated Level Definition Register (#12) while
the register #13 is restored with the non-modulated
level definition value.
ams Datasheet, Confidential: 2013-Oct [3-02]
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