Single output convert to differential output at LNA

[eason.RFIC]

i design a LNA with single output , but now i want to connect it with mixer , the mixer is a differential input , so i must convert single output at LNA to differential ! i know a balun can achieve this ,and are there any other method to achieve the convert ....thanks[/SIZE]

 

[DDavid]

So what is question?

 

[BigBoss]

If you bandwidth is not too large, you can obtain diff. signals by implementing a circuit single ended-to-differential converter.
You can find such circuits on the internet.But your frequency and bandwidth shouldn't be too high because these circuits can not maintain phase and amplitude balance overall very large band.

 

[biff44]

You can use a lumped element lp/hp diplexer structure to change single ended into differential signals. You get 90 degrees phase shift from one arm, and -90 from the other, so it looks like two signals 180 degrees apart. Narrowband though.

There are chip baluns that do this, including some that have bandpass filters built in. Very popular at 2.45 Ghz band.

A FET device, with Source to ground resistor, and with drain to +V resistor, can be used as an active balun.

If performance is not critical, you can connect one of the mixer inputs to ground (probably thru a blocking cap) and treat the other input as single ended input. Will increase apparent conversion loss though.