Hello,

Recently at college we've been looking at QPSK, PSK, BPSK, etc. And I've been trying to find circuit that perform this type of modulation and learn on how they work. I see block diagrams where people put either a 1 or a -1 into a mixer with a signal applied to it and they get PSK out but I can't quite come up with a design that works. I've looked at the gilbert cell... is this a good method for PSK or is there a name of a circuit you guys can refer me too to get PSK???

Thanks

 

Page 23 onwards,
ee.eng.usm.my/eeacad/mandeep/EEE436/CHAPTER2.doc‎

Ramesh

 

Hello Ramussons

The link you gave does not work???

Thanks

 

www.ee.eng.usm.my/eeacad/mandeep/EEE436/CHAPTER2.doc‎

Ramesh

 

Never heard of a Gilbert cell till now. Wow, what a simple four quadrant multiplier.

That seems like a good circuit to me as long as you keep the input voltage levels appropriately low. (Look it up in Wikipedia.) It won't work if the frequency is too high for the transistors.

What we always do is use a balanced mixer, which is a passive device comprised of four diodes and a couple of toroidal transformers. Mini-Circuits sells them. They also sell them housed in a little metal box with BNC connectors for inputs and outputs. They work just fine and you can get an appropriate one for virtually any frequency range.

 

Great, I believe you are talking about ring modulators... But is it possible to get diodes that work well in the 70 MHz range???

Thanks