Radio receiver having compensation for direct current offset

A radio receiver providing compensation for a direct current offset including:

• a first frequency converting means for converting a signal received by the radio receiver to first and second intermediate frequency signals each having an angular frequency ωr, said first and second intermediate frequency signals being in phase quadrature with respect to each other;
• analog-to-digital converting means for converting said first and second intermediate frequency signals to first and second intermediate frequency digital signals each having said angular frequency ωr, said first and second intermediate frequency digital signals being in phase quadrature with respect to each other and including the direct current offset which is generated within said analog-to-digital converting means;
• second frequency converting means for converting said first and second digital signals and said direct current offset to first and second baseband signals, wherein said second frequency converting means includes:
• a cosine ROM for storing a cosine waveform having said intermediate frequency ωr;
• a sine ROM for storing a sine waveform having said intermediate frequency ωr;
• a first multiplier for multiplying said cosine waveform and said first digital signal;
• a second multiplier for multiplying said sine waveform and said first digital signal;
• a subtractor for subtracting an output of said second multiplier from an output of said first multiplier and for outputting said first baseband signal;
• a third multiplier for multiplying said sine waveform and said first digital signal;
• a fourth multiplier for multiplying said cosine waveform and said second digital signal;
• and
• an adder for adding an output of said third multiplier and an output of said fourth multiplier and for outputting said second baseband signal;
• and
• low pas filtering means having a cutoff frequency ωr for removing frequency components of said first and second baseball signals which are higher than ωr.

A radio receiver providing compensation for a direct current offset including:

• a first frequency converting means for converting a signal received by the radio receiver to first and second intermediate frequency signals each having an angular frequency ωr, said first and second intermediate frequency signals being in phase quadrature with respect to each other;
• analog-to-digital converting means for converting said first and second intermediate frequency signals to first and second intermediate frequency digital signals each having said angular frequency ωr, said first and second intermediate frequency digital signals being in phase quadrature with respect to each other and including the direct current offset which is generated within said analog-to-digital converting means;
• second frequency converting means for converting said first and second digital signals and said direct current offset to first and second baseband signals, wherein said second frequency converting means includes:
• a cosine ROM for storing a cosine waveform having said intermediate frequency ωr;
• a delay circuit coupled to said cosine ROM, said delay circuit delaying the output of said cosine ROM by π/2;
• a first multiplier for multiplying said cosine waveform and said first digital signal;
• a second multiplier for multiplying an output of said delay circuit and said second digital signal;
• a subtractor for subtracting an output of said second multiplier from an output of said first multiplier and for outputting said first baseband signal;
• a third multiplier for multiplying the output of said delay circuit and said first digital signal;
• a fourth multiplier for multiplying said cosine waveform and said second digital signal;
• and
• an adder for adding an output of said third multiplier and an output of said fourth multiplier and for outputting said second baseband signal;
• and
• low pass filtering means having a cutoff frequency ωr for removing frequency components of said first and second baseband signals which are higher than ωr.

A radio receiver providing compensation for a direct current offset including:

• a first frequency converting means for converting a signal received by the radio receiver to first and second intermediate frequency signals each having an angular frequency ωr, said first and second intermediate frequency signals being in phase quadrature with respect to each other;
• analog-to-digital converting means for converting said first and second intermediate frequency signals to first and second intermediate frequency digital signals each having said angular frequency ωr, said first and second intermediate frequency digital signals being in phase quadrature with respect to each other and including the direct current offset which is generated within said analog-to-digital converting means;
• second frequency converting means for converting said first and second digital signals and said direct current offset to first and second baseband signals, wherein said second frequency converting means includes:
• a controller;
• and
• first and second sign inverters coupled to said controller, said first and second sign inverters receiving said first and second digital signals respectively, the signs of said first and second digital signals at outputs of said first and second sign inverters being determined by said controller;
• the outputs of said first and second sign inverters outputting said first and second baseband signals;
• and
• low pass filtering means having a cutoff frequency ωr for removing frequency components of said first and second baseband signals which are higher than ωr, wherein said low pass filtering means is a transversal filter.