What are the general tradeoffs of using a transformer for this purpose as opposed to an active circuit? I'm curious.
1) balun is passive, no power consumption
2) a really broadband balun (3GHz) is still cheap, a broadband active circuit will cost more (you need find a really good broadband amp_)
3) a balun does not introduce any distortion......
4) Selecting the wrong active LO driver circuit can cause a variety of problems in the mixer (noise, conversion gain, LO leakage, distortion etc). So using a passive balun it's a lot easier to get the performance out of the device that is specified in the datasheet datasheet unless you worked with mixers before and are familiar with all the effects the LO signal can have on your desired output signal.