Suppose you have a device such as a wireless video camera and the only way to power on the device is by way of RF. If the video camera has a CPU how can the baseband IC power up this CPU ? Is it possible to embed the baseband IC's with some ASIC integrated circuits (Boolean logic gates) with the capability of processing the data (command to start up the CPU) which the RF wave is carrying ?
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\$\begingroup\$ Other than with an interrupt? \$\endgroup\$– Ignacio Vazquez-AbramsCommented May 19, 2016 at 2:38
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2 Answers
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The only way I'm aware of (except for rfid, but that's a special case) is that the RF section is always on and triggers a 'wake-up' interrupt when it recieves a data packet. The interrupt fires up the cpu so it can then ask the radio what happened.
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Some cameras can use 'phantom' power that is imposed on the RF cable itself, much like some microphones use phantom power.
The difference between the usable frequencies and DC power is so great that it is easy for simple RCL filters to separate the power from the signal at both ends of the cable, whether it is RF coax or 600 ohm cable with XLR connectors.
If the camera (or microphone) has no external power then it must have lithium or other high quality batteries that should be replaceable. RFID techniques only have a range of maybe 1 meter, and the RF power is very weak, even compared to Bluetooth.