| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a cable MODEM wherein a tuner can receive a signal received by an input terminal, apply frequency conversion to the signal, a QAM demodulator can demodulate the resulting signal and normally output, and even when a signal with an excess level is given to the input terminal, the tuner can receive the signal with a proper level and can be normally in operation. <P>SOLUTION: An attenuation means provided with attenuator elements whose attenuation is adjustable is interposed between the input terminal and the tuner and configured to transmit the normally attenuated signal to a next stage, the tuner includes: an electric field strength measurement means for measuring an input signal level and outputting it; and a control means for executing a step wherein measured signal level information items are received, the total sum is calculated, and the total sum of the signal level information items is compared with a first threshold value, a step wherein a level of an optional wave in the signal level information items is compared with a second threshold value, and for outputting a switching control signal for decreasingly switching the attenuation amount of the attenuator elements to an attenuation means when the total sum is equal to or less than the first threshold value and the signal level of the one wave is equal to or less than the second threshold value. <P>COPYRIGHT: (C)2007,JPO&INPIT |
