Phase Encoding
Phase Encoding (usually given as the acronym, PE) is an encoding technique which is commonly used on magnetic storage.
In PE, there is a change in direction of the magnetic field flux in the middle of every bit-time; whether a particular bit is '0' or '1' is indicated by the direction of the flux transition.
The disadvantage of PE is that if there are two consecutive bits of the same value, there must be reversal in the flux direction, from that resulting from the storage of the first bit (back to the opposite direction), at around the end of the first bit's clock time, so that the appropriate change in flux direction can be made at the next bit-time. Obviously, if there were a long string of bits of the same value, this would repeat; this means that the magnetic medium had to be capable of supporting a rate of twice as many changes in the direction of magnetization as the rate of the raw data to be stored on it.
