Anaren AIR Module, Users Manual
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3.5.
Power Supply Considerations
Noise on the power supply line reduces the sensitivity of a receiver and modulates onto a transmitters
signal, both of which causes a degradation of link quality and hence a reduction in range.
The A1101R09A and A1101R09C radio modules have integral ferrite bead in the supply line from pin 18
(Vdd) and decoupling capacitance to reduce any noise on the incoming power supply line. This
arrangement will take care of most supply voltage noise. In particular noisy environments (switching
regulators, motor controls, etc.) it may be necessary to add additional noise reduction means.
Pin 7 (Vdcoup1) is connected to the modules internal supply line after the ferrite bead and decoupling
capacitors and can be used to probe the noise at module level. The noise level measured on pin 7 should
not exceed 120mVpp when in transmit or receive mode, it may however exceed this value when setting
up or accessing data to/from the FIFO’s while not actively transmitting or receiving.
If the level measured is exceeding the above limit means should be taken to ensure maximum range:
•
Add decoupling capacitance to pin 7 (Vdcoup1).
•
Add additional filtering in the supply line.
•
Add an LDO in the supply line (the TPS731xx low Dropout Regulator from TI is recommended)
