from what i've read about passive 3dtv (specifically the LG LD950) it uses a filter polarised in alternating directions on each line with left/right images interlaced. this means a max of 1080i instead of the 1080p you can get with active glasses why not place a circular polarising liquid crystal filter (like those used for some 3d cinema projectors) over the screen? this would allow the same alternate frame display system as for active glasses TVs but moves the filter from the glasses to the TV. supposedly the need for a filter aligned with the horizontal rows of pixels on the screen results in the current passive glasses TVs being more expensive than active glasses based ones. not sure what the difference in manufacturing cost between this system and the one LG are currently using would be but it would at least allow 1080p 3d without expensive active glasses.
Welcome to the forums milkkart . Yes, that is possible and some smaller monitors use this - although I've not seen a large TV do this yet. IIRC, it's the recent batch of Zalman 3D monitors that use circular polarization. Perhaps we'll see this rolled out on to larger displays in the future. Good to have another 3D TV enthusiast on the forums!