Patent ID: 7791395

Claim:
A DC offset correcting device for correcting a DC offset of a frequency converter, comprising: a signal generator connected to the frequency converter for generating a test signal including a first signal having a predetermined amplitude from a reference voltage in a first direction and a second signal having the same amplitude as the first signal from said reference voltage in a second direction opposite the first direction, correcting a DC level of the test signal based on a DC offset correcting signal supplied thereto, and supplying the corrected test signal to the frequency converter; an amplitude detector connected to the frequency converter for detecting the amplitudes of the first and second signals of the test signal processed by the frequency converter; a level compressor connected to the amplitude detector for converting in level the amplitudes of the first and second signals which are detected by said amplitude detector, with a gain variable depending on an input level thereto; a comparator connected to the level compressor for comparing the amplitudes of the first and second signals which are converted in level by said level compressor, with each other; and an offset adjuster connected to the comparator and the signal generator for generating said DC offset correcting signal depending on a compared result from said comparator, and supplying the DC offset correcting signal to said signal generator.