Hi Kelly,


what kind of application are you looking at? Personally I can't imagine predistortion being used in a receiver. Also, passive mixers are already quite linear.


cheers,
Aaron

Hi Kelly,


the method you described for the pre-distortion sounds interesting. However, I still have a lot of doubts. First of all, in a passive mixer, the switch changes bias point over pretty much the full range. So it isn't really correct to talk about whether it's biased in the subthreshold region or the strong inversion region. It is more meaningful to talk about the duty cycle (in my opinion). That said, I'm not saying the idea doesn't work.

Another thing to consider is that using this technique, you are increasing the series resistance of the switch. You can compensate it by widening the devices, but this will increase the capacitance. If you are considering adding additional LC filtering at baseband, then you must be looking at a very wide signal bandwidth since inductors are usually used at very low frequencies (on-chip anyway).

Lastly, I have seen a few papers where people talk about trying to cancel the positive gm" with negative gm", but I seriously doubt their robustness to variation.

I think I recall seeing some kind of bootstrap technique using capacitors, but can't recall enough of the details to comment. It does sound more reliable, but you have to make sure its suitable for your application.


hope it works out for you,
Aaron