Abstract: The invention arranges an auxiliary antenna in the neighborhood of an antenna, and a voltage applied to the auxiliary antenna is changed based on the reception quality of a received signal received by the antenna. Thereby, the reception characteristic of the antenna is changed. Moreover, the optimum antenna is selected among a plurality of arranged antennas based on the reception quality of the received signals received by the plurality of arranged antennas.

Abstract: The invention arranges an auxiliary antenna in the neighborhood of an antenna, and a voltage applied to the auxiliary antenna is changed based on the reception quality of a received signal received by the antenna. Thereby, the reception characteristic of the antenna is changed. Moreover, the optimum antenna is selected among a plurality of arranged antennas based on the reception quality of the received signals received by the plurality of arranged antennas.

Abstract: In order to realize a demodulator circuit and a demodulation method of controlling the amplification degree of an AGC in order that the optimum C/N value near the best C/N value can be always secured in the whole AGC voltage region, the amplification degrees of AGC's 122 and 126 is controlled based on a change of the reception grade of a received signal having been outputted from a FFT 132 of a demodulator circuit unit 13 after being received by an antenna 11 and being amplified by a tuner unit 12. Consequently, the amplification degree can be immediately modified according to a change of the reception grade, and consequently the optimum reception grade can be secured always.