| 摘要 |
PURPOSE:To attain automatic offset correction with high accuracy repeating the operation of correcting a differential offset in the negative direction when the offset detected by a voltage comparator is positive and in the positive direction when the offset detected by the voltage comparator is negative in the non-transmission so as to reduce the differential offset. CONSTITUTION:A differential offset is detected in the non-transmission state in the usual operation mode, generated correction data are added to input transmission data and the sum is inputted to a D/A converter 206, in which the data are converted into analog data, which are inputted to an orthogonal modulator 213. In the correction data generating mode, a sum of 1-all 0 signal and correction data is inputted as an input of the converter 206 so that a noninverting output and an inverting output are identical to each other and the output in the buffer 208 is detected by a voltage comparator 209. When the offset is positive, correction data are reduced by one step and when negative conversely, the correction data are increased by one step. The operation above is repeated till the offset reaches a detection limit of the comparator to generate correction data. |
