| 摘要 |
<p>A digital receiver has a bandpass delta-sigma AD converter for analog-to-digital converting a modulated wave signal in the analog domain to a signal in the digital domain, and an object is a reduction in thermal noise and a reduction in power consumption in the bandpass delta-sigma AD converter. A signal level detection section 9a detects the level of the IF signal SIF and a current control section 10 are provided. The current control section 10 adjusts, based on the detection result DETa of the signal level detection section 9a, the operating current of an operation amplifier serving as delay means which is a structural component of a switched-capacitor filter 7b provided in the bandpass delta-sigma AD converter 7. As the electric field strength induced in the antenna 1 reduces, the level of the IF signal SIF becomes smaller. The smaller the level of the IF signal SIF, the lower the operating current of the operation amplifier is set, resulting in a reduction in the power consumption. As the electric field strength induced in the antenna 1 increases, the level of the IF signal SIF becomes larger. The larger the level of the IF signal SIF, the higher the operating current of the operation amplifier is set, resulting in a reduction in thermal noise.</p> |
