Patent ID: 6246732
Filing Date: 2001-06-12
Classification: H04L

Abstract:
A demodulator for constituting a digital communication receiver, comprising:a detector for converting a digital received signal into a base band signal;an unnecessary frequency component removal means for removing unnecessary frequency components from a signal supplied from said detector thereby to output a signal from which the unnecessary components has been thus removed;a delay spread calculation means for obtaining a measured value of delay spread of the output signal supplied from said unnecessary frequency component removal means;a threshold storage means storing a threshold of delay spread therein;an adaptive equalizer for performing adaptive equalization on the output signal supplied from said unnecessary frequency component removal means;a decoding means for decoding an input signal; anda switching means; wherein said delay spread calculation means includes:a training symbol storage means storing a training symbol therein;means for obtaining impulse response of a path channel of said received signal on the basis of said training symbol supplied from said storage means and the output signal supplied from said unnecessary frequency component removal means; andmeans for obtaining a measured value of delay spread on the basis of the obtained impulse response; and wherein said switching means supplies the output signal from said unnecessary frequency component removal means to said decoding means through said adaptive equalizer when the obtained measured value of delay spread is larger than the threshold stored in said threshold storage means, while supplies the output signal from said unnecessary frequency component removal means to said decoding means without being passed through said adaptive equalizer when the obtained measured value of delay spread is not larger than said threshold.