| 摘要 |
A front end module is provided to compensate an offset of a sampled signal by performing a function of a QDD(Quadrature Digital Downconverter) without changing a sink block. A front end module includes an analog/digital converting unit(21), a QDD unit(22), a first phase rotator(23), an FFT(Fast Fourier Transform) module(26), a demodulation unit(27), a second phase rotator(29), and a selector(28). The analog/digital converting unit samples each of a plurality of different intermediate frequencies using one sampling frequency, and converts the sampled signal into a digital signal. The QDD unit performs a down conversion of the signal outputted from the analog/digital converting unit to a base band signal. The first phase rotator compensates an offset of a predetermined signal of the signals from the QDD unit using a synchronization signal. The FFT module performs an FFT for the signal of the first phase rotator, and changes an output sequence in response to the intermediate frequency. The demodulation unit demaps the signal of the FFT module on an I-Q quarter plane. The second phase rotator rotates I and Q values of the signal of the demodulation unit at the I-Q quarter plane to be matched with a previous phase. The selector selects one of the signal of the demodulation unit and the signal of the second phase rotator.
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