the library systems i am very familiar with - have a look at this ==> http://www.ti.com/rfid/docs/manuals/appNotes/HFAntennaDesignNotes.pdf (section 8 in particular) as it relates some knowledge about reading HF tags in unknown orientations - this kind of a system i have miniturized, too - but for a doorways and the like, with HF, you would need a pair of antennas like these ==> http://www.feig.de/en/products/obid/product-areas/obid-i-scan-hf/long-range-antennas/id-iscant1700740-clear-gate.html and a high power reader to go with it (Feig also sells these and we used these in conjunction with the antennas described in the design notes pdf link. You would also want to use the largest tag possible as well - usually our ISO15693 45mm x 45mm square tag or larger works great in these kinds of applications. The drawback of course is the cost - for a home, usually no one can spend 10k+ just to get in their house automatically - this is why either using a known orientation approach (like making the user present a tag or fob) is best way overall - you can still get good range (using the TRF79xx parts) using this approach if you choose right size antenna (maybe 300mm x 300mm max, for about 10-12" range), with ISO15693 tags of reasonable size.