avishay said:
Hello
I have to send a high speed (~600 Mbit/s), bidirectional LVDS signal on
a single twisted pair line. I wonder if it can be done by using
something that works like a telephone hybrid transformer. Is such a
design possible? Does anybody knows about example or components for
such a design?
Thanks, Avishay
If you want to do 600Mbps in *both* directions simultaneously (over one
path) then you'll have to do something along the lines of the telephone
hybrid transformer.
I've never attempted this type of rate using a hybrid (sometimes called
transhybrid) transformer technique, but it should be possible. You'll need
this type of transformer at each end of the twisted pair.
The main reason why it might be possible is because destination path
impedance is known and fairly stable. This is what allows the transformer
circuit to subtract-out each side's own transmit signal from full-duplex
path.
You could also (theoretically) use an active technique (e.g., opamps), but
getting this to work at this speed might be tricky, although easier to put
together.
Do some searching and you'll find the transformer and opamp topology. You'll
probably have to design and wind your own transformer, if you go this route.
If you use the transformer technique, it will also be necessary to encode
(and decode) your data to ensure a minimum number of edges per group of
bits. This will keep any DC component out of the signal (which can't be
passed by a transformer). 8b10b or 64b66b encoding/decoding techniques are
two examples of this.
Bob