| 摘要 |
<p>Provided is a low IF type receiver that, even if any image signals in addition to a desired signal are existent, can measure an image removal ratio without any increases of power consumption and chip area, which would otherwise accompany the provision of a high frequency signal source, encoders and so on, thereby performing calibrations of I/Q mismatches including the I/Q mismatch of a quadrature mixer. A signal path switching unit (13) sequentially switches the signal input paths of I- and Q-signals of IF frequency band, which are generated by a quadrature mixer (11), to the I- and Q-filters (141, 142) of a complex filter (14). At this moment, a calculating unit (16) calculates an image removal ratio on the basis of the signal intensity of an output signal of the I-filter (141) detected by a signal intensity detecting unit (15) each time the signal paths are switched, and further an element value control unit (17) adjusts the element values of the complex filter (14) in such a manner that maximizes the image removal ratio to be calculated, thereby performing an I/Q mismatch calibration. Instead of the adjustment of the element values of the complex filter (14), the adjustment of the element values of the quadrature mixer (11) may be performed or the adjustment of the output phase of the a local oscillator (12) may be performed.</p> |
