Hmmm... "Driveway gate?" Would that be what people commonly call a garage door?"
I use these:
https://www.smarthome.com/seco-larm-e-9660-8b25-enforcer-curtain-ir-motion-sensor-8-beams-black.html
I use the one with 8 beams and its just about the length of the door. It works well, but it has this annoying characteristic that when it is blocked, the relay "clicks" about once per second. Also I do wish it had more beams as they are about 7" apart. Much cheaper than the Miller Edge.
My car has a hatch that opens and I wanted to make sure that was sensed and this works.
Looks like this is 1/4 the price of the Miller Edge. That seems a bit overpriced, if you ask me.