Patent ID: 8194806

Claim:
A demodulation device for demodulating a digital broadcast wave, which is a broadcast wave of digital terrestrial broadcasting, the digital broadcast wave being received by a tuner section, said demodulation device comprising: broadcast wave determining means for determining whether or not there is a broadcast wave in a certain channel, in accordance with an intensity of a signal outputted from the tuner section; digital broadcast wave determining means for determining, in a case where the broadcast wave determining means determines that there is a broadcast wave in the certain channel, whether or not the broadcast wave is a digital broadcast wave, the determining being made in accordance with the signal outputted from the tuner section; an automatic gain control section for performing a primary output gain control on the tuner section so that the tuner section has a constant output; and gain setting means for causing the automatic gain control section to stop the-the primary output gain control, and for causing the automatic gain control section to set an-a secondary output gain of the tuner section so that the tuner section has a greater output than the output obtained while the tuner section is subjected to the primary output gain control by the automatic gain control section, wherein the broadcast wave determining means determines that there is a broadcast wave in the certain channel, when the intensity of the signal, which is outputted from the tuner section in accordance with the secondary output gain to which the gain setting means causes the automatic gain control section to set, reaches a predetermined threshold value or more, and the secondary output gain is a maximum amplifiable value of the tuner section.