Pulse code bit cell demodulation

A method of demodulating a pulse width modulated signal previously modulated with at least one data value selected from the group consisting of first and second values, said pulse width modulated signal comprising at least one bit cell corresponding to said at least one data value, each of said bit cells comprising a first period and a second period, said first period having a first duration and said second period alternatively having a second duration or a third duration in correspondence with said corresponding data value being, alternatively, said first value or said second value, said method comprising the steps of:

• for each of said bit cells:
• initializing an actual count value to a first count value;
• repetitively sampling said pulse width modulated signal at first intervals during said first period of said bit cell;
• adjusting said actual count value by a first increment at each of said first intervals;
• detecting an end of said first period and, in response thereto, using said adjusted actual count value and an expected count value to determine a corrected count value;
• repetitively sampling said pulse width modulated signal at second intervals during said second period of said bit cell;
• adjusting said corrected count value by a second increment at each of said second intervals;
• detecting an end of said second period and, in response thereto, generating a signal alternatively having a first value or a second value in correspondence with said adjusted corrected count alternatively being greater than or not greater than a reference value.

An apparatus for demodulating a pulse width modulated signal previously modulated with at least one data value selected from the group consisting of first and second values, said pulse width modulated signal comprising at least one bit cell corresponding to said at least one data value, each of said bit cells comprising a first period and a second period, said first period having a first duration and said second period alternatively having a second duration or a third duration in correspondence with said corresponding data value being, alternatively, said first value or said second value, said apparatus comprising:

• first sensing means for sensing an actual duration of said first period of said bit cell;
• first count means, coupled to said first sensing means, for generating an actual count value that is proportional to said actual duration of said first period of said bit cell;
• count correction means, coupled to said first count means, for using said actual count value and an expected count value to determine a corrected count value;
• second sensing means for sensing an actual duration of said second period of said bit cell;
• second count means, coupled to said count correction means and said second sensing means for adjusting said corrected count value by an adjustment amount to produce a final adjusted count, said adjustment amount being proportional to said actual duration of said second period of said bit cell;
• and
• signal generating means, coupled to said second count means, for generating a signal alternatively having a first value or a second value in correspondence with said final adjusted count alternatively being greater than or not greater than a reference value.