Image Number 4 for United States Patent #8489030.
A radio apparatus capable of correcting a direct current offset with high accuracy in a short time is provided. A radio apparatus according to an embodiment includes a first amplifier amplifying a signal inputted to an input terminal with amplification gain determined by a variable resistor to generate a first amplified signal, and a second amplifier amplifying the first amplified signal to generate a second amplified signal. Further, the radio apparatus includes a first correcting unit correcting a direct current offset of the first amplifier, and a second correcting unit correcting a direct current offset of the second amplifier. The radio apparatus also includes a reference voltage source or reference current source supplying a reference voltage or reference current for referring a direct current offset to the first amplifier and the second amplifier, a gain controller controlling the amplification gain of the first amplifier; and a correction controller controlling the gain controller to set the amplification gain to maximum and controlling the first and second correcting units to perform correction of the second correcting unit based on the second amplified signal obtained by inputting the reference voltage or the reference current to an input terminal of the second amplifier, and thereafter perform correction of the first correcting unit based on the second amplified signal obtained by inputting the reference voltage or the reference current to an input terminal of the first amplifier.