Patent ID: 7336936
Filing Date: 2008-02-26
Classification: H04B

Abstract:
1. A radio signal receiving apparatus for receiving radio signals each having a base band signal component, comprising: radio signal amplifying means for amplifying said radio signals each having a signal level; base band signal producing means for producing base band signals respectively indicative of said base band signal components of said radio signals amplified by said radio signal amplifying means, said base band signals each having a signal level; controlling means for controlling said radio signal amplifying means to have said radio signal amplifying means amplify said radio signals in response to said signal level of each of said base band signals to be produced by said base band signal producing means; base band signal selecting means for periodically selecting one of said base band signals from among said base band signals produced by said base band signal producing means in response to said signal level of each of said radio signals; and base band signal outputting means for outputting said base band signal periodically selected by said base band signal selecting means to an exterior device, wherein said controlling means includes a signal level calculating unit for calculating a signal level value indicative of said signal level of each of said base band signals to be produced by said base band signal producing means, and a signal level difference calculating unit for calculating a signal level difference between said signal level value of each of said base band signals calculated by said signal level calculating unit and a target value before calculating a gain control value indicative of an absolute value of said signal level difference between said signal level value of each of said base band signals and said target value, said controlling means is operative to control said radio signal amplifying means to have said radio signal amplifying means amplify said radio signals in response to said gain control value calculated by said signal level difference calculating unit, said base band signal selecting means includes: a signal level judging unit for judging whether or not each of said gain control values calculated by said signal level difference calculating unit in association with each of said base band signals is smaller than a predetermined signal level; and said base band signal selecting means is operative to select one of said base band signals from among said base band signals produced by the base band signal producing means after judging whether or not said gain control value calculated by said signal level difference calculating unit in association with each of said base band signals is smaller than said predetermined signal level based on results judged by the signal level judging unit, said base band signals including first and second base band signals respectively having first and second signal levels, said gain control values including first and second gain control values respectively indicative of the absolute value of said signal level difference between said first signal level of said first base band signal and said predetermined target signal level and the absolute value of said signal level difference between said second signal level of said second base band signal and said predetermined target signal level, said first and second gain control values varied in response to a time axis, and respectively having first and second fluctuations, said first and second gain control values respectively in association with said first and second base band signals, said base band signal selecting means includes: candidate signal selecting means for selecting said first and second base band signals from among said base band signals produced by said base band signal producing means after deciding that said first gain control value in association with said first base band signal is smaller than said gain control value in association with each of said base band signals, and said second gain control value in association with said second base band signal is smaller than said gain control value in association with each of said base band signals except for said first base band signal; gain control value difference calculating means for calculating a gain control value difference between said first gain control value in association with said first base band signal selected by said candidate signal selecting means and said second gain control value in association with said second base band signal selected by said candidate signal selecting means; first judging means for judging whether or not said gain control value difference between said first gain control value and said second gain control value calculated by said gain control value difference calculating means is larger than a predetermined threshold value; and second judging means for judging whether or not said fluctuation of said first gain control value in association with said first base band signal is larger than said fluctuation of said second gain control value in association with said second base band signal, said base band signal selecting means is operative to periodically select said first base band signal from among said base band signals produced by said base band signal producing means when the judgment is made by said first judging means as said gain control value difference between said first gain control value and said second gain control value calculated by said gain control value difference calculating means being larger than said predetermined threshold value, and select one of said first and second base band signals from among said base band signals produced by said base band signal producing means based on results judged by said second judging means when the judgment is made by said first judging means as said gain control value difference between said first gain control value and said second gain control value calculated by said gain control value difference calculating means being equal to or smaller than a predetermined threshold value.