| 摘要 |
<p>PROBLEM TO BE SOLVED: To improve the reception sensitivity of a reception signal by operating a low-noise amplifier(LNA) provided at a front end of a VCR tuner under various conditions. SOLUTION: A control section 16 controls the operation of a LNA 111 of an amplifier section 11 according to various factors, such as a comparison result signal from a comparator section 15 and a VCR setting mode VCR/TV signal to discriminate an electric field strength of a received channel. Then an RF-AGC voltage VAGC becomes lower, when a signal from an antenna 10 indicates a high electric field strength, and the RF-AGC voltage VAGC becomes higher when a signal from the antenna 10 indicates a low electric field strength. The comparator section 15 compares the RF-AGC voltage VAGC with a reference voltage Vref , and if the RF-AGC voltage VAGC is lower than the reference voltage Vref , the processing section 15 provides an output of a low-level comparison result signal, while recognizing a broadcast signal with a high electric field strength. When the RF-AGC voltage VAGC is higher than the reference voltage Vref , the processing section 15 provides an output of a high-level comparison result signal, while recognizing a broadcast signal with a low-electric field strength. Furthermore, a control section 16 activates/deactivates the low-noise amplification operation of the LNA 111, depending on the VCR setting mode VCR/TV signal and the comparison result signal from the comparator section 15.</p> |
