Hi - I was just thinking about this. How does a device in real time
share an antenna between rx and tx circuits?
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In fact for a reliable 2 way communication, say for example for
a packet system could be used.
Look up amateur packet radio for example.
In short the transmitter / receiver is always in receive mode,
When it has data to send, the data is send in the form of a
(SDLC or HDLC) protocol, first a syc pattern, then some data bytes,
then a CRC check.
The length of such a packet can be say 2 kB.
The 'other side' receives and decodes the packet (the sync pattern is
sync a PLL that generates a clock to extract the data), and if the CRC
an ACK message is transmitted after waiting for the channel to be free
for a random amount of time (in case others also want the channel).
If the CRC was not correct a NAK message is send in the same way.
The original transmitter will repeat after some time if it hears
nothing, or send
the next packet if it gets a ACK, or repeat the last packet if it gets
For robotics this is likely the only safe scheme.
You want to make sure the command (to do something) was received
and possible control more then one robot (individually), and allow
feedback from sensors all at the same frequency.
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