Circuit and system challenges in IR wireless communication

IR wireless transceivers pose interesting challenges for circuit design. There are two basic types of IR wireless transmission: 1) directed, where the transmitting device must be pointed at the receiver, and 2) diffuse, where the IR signal is emitted into a large solid angle and receiving devices collect the signal reflected off walls and ceiling, thus requiring little or no pointing. Unlike RF, IR schemes employ baseband modulation. At data rates up to 60 kb/s, amplitude shift keying has been used. At higher data rates, RZI or pulse position modulation data encoding schemes (L-PPM where L is the number of slots) are used for more efficient modulation.