If you go with passive polarized glasses, there is no single projector only solution, as you need two different physicaly optical systems (lenses/filters).
There is a single projector solution though.
An actively alternating polarization filter takes the position of the active glases and 'convertes' the picture for passive polarized ones.
But keep in mind, that this solution has a reduction of the projectors brightness in half of the original. 50% for each eye.
As far as I know, '3D ready' projectors usualy have an option to choose between the 3D modes, 'side by side', 'top - bottom' or interleaved (alternating frames). But every Projector works a little bit different and you should study the specs.
Especialy the side by side may differe by the projectors. While some only take FullHD content (resulting in two times 980 x 1080 scaled to 1920), others may take 4k (but usually you then would need 4k content with two times 1920 x 2140)
In both cases the content is squeezed horizontly to fit next to each other in the full frame. The projector then unsqueezes them and scales it to its native output resolution with alternating the left and right picture.