Frequency offset compensation in a digital frequency shift keying receiver

A method of frequency offset compensation, comprising:

• receiving an input signal wherein frequency offsets have been translated to DC offsets;
• first determining a current maximum peak value of said input signal;
• second determining a current minimum peak value of said input signal;
• calculating, in a communication circuitry, an average of said current maximum peak value and said current minimum peak value to yield a DC offset estimate;
• and
• subtracting said DC offset estimate from said input signal to yield a frequency compensated output signal;
• wherein said step of determining said current minimum peak value comprises the steps of:
• comparing said input signal with a previous minimum peak value;
• if said input signal is not greater than said previous minimum peak value, subtracting a first difference between said previous minimum peak value and said input signal, said first difference multiplied by a minimum discharge coefficient and subtracted from said previous minimum peak value to yield said current minimum peak value;
• and
• if said input signal is greater than said previous minimum peak value, adding said previous minimum peak value to a second difference between said input signal and said previous minimum peak value, said second difference multiplied by a minimum charge coefficient to yield said current minimum peak value.

An apparatus for frequency offset compensation, comprising:

• first means for receiving an input signal wherein frequency offsets have been translated to DC offsets;
• second means for determining a current maximum peak value of said input signal;
• third means for determining a current minimum peak value of said input signal;
• fourth means for calculating an average of said current maximum peak value and said current minimum peak value to yield a DC offset estimate;
• and
• fifth means for subtracting said DC offset estimate from said input signal to yield a frequency compensated output signal;
• wherein said second means for determining said current maximum peak value comprises:
• means for comparing said input signal with a previous maximum peak value;
• means for adding said previous maximum peak value to a first difference between said input signal and said previous maximum peak value, said first difference multiplied by a maximum charge coefficient to yield said current maximum peak value if said input signal is greater than said previous maximum peak value;
• and
• means for subtracting a second difference between said previous maximum peak value and said input signal multiplied by a maximum discharge coefficient from said previous maximum peak value to yield said current maximum peak value if said input signal is not greater than said previous maximum peak value.

An apparatus for frequency offset compensation, comprising:

• first means for receiving an input signal wherein frequency offsets have been translated to DC offsets;
• second means for determining a current maximum peak value of said input signal;
• third means for determining a current minimum peak value of said input signal;
• fourth means for calculating an average of said current maximum peak value and said current minimum peak value to yield a DC offset estimate;
• and
• fifth means for subtracting said DC offset estimate from said input signal to yield a frequency compensated output signal;
• wherein said third means for determining said current minimum peak value comprises:
• means for comparing said input signal with a previous minimum peak value;
• means for subtracting a first difference between said previous minimum peak value and said input signal, said first difference multiplied by a minimum discharge coefficient and subtracted from said previous minimum peak value to yield said current minimum peak value if said input signal is not greater than said previous minimum peak value;
• and
• means for adding said previous minimum peak value to a second difference between said input signal and said previous minimum peak value, said second difference multiplied by a minimum charge coefficient to yield said current minimum peak value if said input signal is greater than said previous minimum peak value.

An apparatus for frequency offset compensation, comprising:

• first means for receiving an input signal wherein frequency offsets have been translated to DC offsets;
• second means for determining a current maximum peak value of said input signal comprising:
• means for comparing said input signal with a previous maximum peak value;
• means for adding said previous maximum peak value to a first difference between said input signal and said previous maximum peak value, said first difference multiplied by a maximum charge coefficient to yield said current maximum peak value if said input signal is greater than said previous maximum peak value;
• and
• means for subtracting a second difference between said previous maximum peak value and said input signal multiplied by a maximum discharge coefficient from said previous maximum peak value to yield said current maximum peak value if said input signal is not greater than said previous maximum peak value;
• third means for determining a current minimum peak value of said input signal comprising:
• means for comparing said input signal with a previous minimum peak value;
• means for subtracting a first difference between said previous minimum peak value and said input signal, said first difference multiplied by a minimum discharge coefficient and subtracted from said previous minimum peak value to yield said current minimum peak value if said input signal is not greater than said previous minimum peak value;
• and
• means for adding said previous minimum peak value to a second difference between said input signal and said previous minimum peak value, said second difference multiplied by a minimum charge coefficient to yield said current minimum peak value if said input signal is greater than said previous minimum peak value;
• fourth means for calculating an average of said current maximum peak value and said current minimum peak value to yield a DC offset estimate;
• and
• fifth means for subtracting said DC offset estimate from said input signal to yield a frequency compensated output signal.

An apparatus for frequency offset compensation, comprising:

• circuitry for means for receiving an input signal wherein frequency offsets have been translated to DC offsets;
• circuitry for determining a current maximum peak value of said input signal;
• circuitry for determining a current minimum peak value of said input signal;
• circuitry for calculating an average of said current maximum peak value and said current minimum peak value to yield a DC offset estimate;
• and
• circuitry for subtracting said DC offset estimate from said input signal to yield a frequency compensated output signal;
• wherein said circuitry for determining said current maximum peak value comprises:
• circuitry for comparing said input signal with a previous maximum peak value;
• circuitry for adding said previous maximum peak value to a first difference between said input signal and said previous maximum peak value, said first difference multiplied by a maximum charge coefficient to yield said current maximum peak value if said input signal is greater than said previous maximum peak value;
• and
• circuitry for subtracting a second difference between said previous maximum peak value and said input signal multiplied by a maximum discharge coefficient from said previous maximum peak value to yield said current maximum peak value if said input signal is not greater than said previous maximum peak value.

An apparatus for frequency offset compensation, comprising:

• circuitry for receiving an input signal wherein frequency offsets have been translated to DC offsets;
• circuitry for determining a current maximum peak value of said input signal;
• circuitry for determining a current minimum peak value of said input signal;
• circuitry for calculating an average of said current maximum peak value and said current minimum peak value to yield a DC offset estimate;
• and
• circuitry for subtracting said DC offset estimate from said input signal to yield a frequency compensated output signal;
• wherein said circuitry for determining said current minimum peak value comprises:
• circuitry for comparing said input signal with a previous minimum peak value;
• circuitry for subtracting a first difference between said previous minimum peak value and said input signal, said first difference multiplied by a minimum discharge coefficient and subtracted from said previous minimum peak value to yield said current minimum peak value if said input signal is not greater than said previous minimum peak value;
• and
• circuitry for adding said previous minimum peak value to a second difference between said input signal and said previous minimum peak value, said second difference multiplied by a minimum charge coefficient to yield said current minimum peak value if said input signal is greater than said previous minimum peak value.