An analog front-end circuit transmits and receives data between a baseband circuit and a radio unit. An analog-to-digital converter converts an analog received signal output from the radio unit into a digital signal. An interpolator interpolates an output signal of the analog-to-digital converter by up-sampling the output. A .SIGMA..DELTA. modulator performs a fourth-order .SIGMA..DELTA. modulation on an output signal of the interpolator. A low-voltage differential signal transmitter converts an output signal of the .SIGMA..DELTA. modulator into a low-voltage differential signal and transmits the converted signal to the baseband circuit via differential signal lines.