1. A radio apparatus using a plurality of antennas to receive a signal, comprising: a plurality of analog circuits provided to correspond to said plurality of antennas and subjecting signals received at said plurality of antennas, respectively, to an analog signal processing; a plurality of analog-digital converters receiving signals from said plurality of analog circuits, respectively, to convert said signals to digital signals; a plurality of filter means receiving said digital signals from said plurality of analog-digital converters, respectively, to filter said digital signals to compensate for distortion in waveform resulting from a difference of a characteristic between said plurality of analog circuits; and digital signal extraction means receiving signals from said plurality of filter means, respectively, to subject said signals to a digital signal processing to extract a received signal.