Method and apparatus for decoding F2F signals read from a magnetic data carrier

Device for decoding signals coded in F2F manner on a magnetic data carrier comprising:

• A) a reading station including a magnetic reading head for reading magnetically recorded signals to generate analog head signals;
• B) an amplifier station with a very high gain for amplifying said analog head signals;
• C) a discriminating and integrating station for generating a discriminated and binary looking signal;
• D) a reference time acquisition station for setting a fixed or variable start-up time value;
• E) a phase estimating station for estimating the correct end of a bit cell beginning from said start-up time value, and
• F) a symbol correlation station for correlating the received binary signal stream (r(t)) with all possible symbol combinations (ui(t)) based on said estimated phase for generating a bit stream, wherein said symbol correlation station contains an overlap decoder for correlating the signals under inclusion of previous correlation results.

Method for decoding F2F signals that are read from a magnetic data carrier with the help of a magnetic reading head, comprising the following steps:

• a) amplifying the analog signal read by said magnetic reading head using an amplifier of very high gain;
• b) discriminating said analog signal by applying a clip level to generate a received digital signal (r(t)) out of said analog signal;
• c) estimating the phase of said digital signal relative to a certain reference point (start-up time value) for determining the end of a bit cell to generate an estimation interval;
• and
• d) correlating said received digital signal against all possible symbol combinations during a correlation interval by integrating over the correlation interval (T) the product of a possible symbol combination (ui(t))--a sample--and said received digital signal (r(t)) ##EQU2## whereby this integration results in a number, performing this integration for all possible symbol combinations, and selecting the maximum result as the one coming closest to the real symbol.

Method for decoding F2F signals that are read from a magnetic data carrier with the help of a magnetic reading head, comprising the following steps:

• a) amplifying the analog signal read by said magnetic reading head using an amplifier of very high gain;
• b) discriminating said analog signal by applying a clip level to generate a received digital signal (r(t)) out of said analog signal;
• c) estimating the phase of said digital signal relative to a certain reference point (start-up time value) for determining the end of a bit cell to generate an estimation interval;
• and
• d) correlating said received digital signal against all possible symbol combinations during a correlation interval by multiplying two signals (ul(t), u2(t)) as binary signals of the same signal level (+1 or -1) to form a third signal (s(t)), said third signal being integrated over an estimation interval (T) by simply calculating the difference of the time where the function is on the same level with that time where the function is on the different level ##EQU3##