rfid

i want to build 1 from scratch for my last year of college, the tags i have are 13.56 mhz and want about 5ft of range so that as i walk upto my door the scanner reads the tag and unlocks the door

I think you are pushing s**t up hill wanting a 5 foot range.

It can be done but would require a BIG antenna coil and a lot of power to drive it. (like 3 foot square)

Not a very practical application for a door lock.

One source of information you could try is Texas Instruments, and run a few searches for the RFID frequency you need. as they have many dedicated chips and circuit information to suit.

I think you will find a 5 inch range will be more realistic for your project.

I have never worked with the 13.56 mhz range and know nothing about their limitations.

Pete.