SA602/SA612 drive with external square wave oscillator how to

Hello,
I was wonderign if the SA602 (or SA612) can be driven with an external square wave oscillator instead of a sine wave.

You can drive the SA602 with sine or square wave LO signal, and it will work. Only make sure the LO power does not exceed the specification.
As such signal contains harmonics, the converter will respond to harmonics, too. If this is not desired, use band-pass or low-pass filters in RF and LO inputs.

Thanks. So in a square wave, if I put an LPF it will become a sinewave, since harmonics are filtered?

Yes, true.
MOst of those integrated mixers operate with sine or square-wave signals.

If the internal transistors of the Gilbert cell mixer are not biased to work in saturation (and in SA612 case, they are not) is preferable to drive the mixer at the LO input using a sine wave signal.
There are many switching-type mixers where is mandatory to use square LO signal, but this is not valid for some of Gilbert cell IC mixers.