Patent ID: 6308057
Filing Date: 2001-10-23
Classification: H04B

Abstract:
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 .omega..sub.r, 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 .omega..sub.r, 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 generator for generating cosine waveform having said intermediate frequency .omega..sub.r,a sine generator for generating a sine waveform having said intermediate frequency .omega..sub.r ;a first multiplier for multiplying said cosine waveform and said first digital signal;a second multiplier for multiplying said sine waveform 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 said sine waveform and said first digital signal;a fourth multiplier for multiplying said cosine waveform and said second digital signal; andan adder for adding an output of said third multiplier and an output of said fourth multiplier and for outputting said second baseband signal; andlow pass filtering means having a cutoff frequency .omega..sub.r for removing frequency components of said first and second baseband signals which are higher than .omega..sub.r.