| 摘要 |
PURPOSE:To make possible the control of a reception input level without increasing the number of components by decreasing the base bias of low noise amplification and operating a switch so as to decrease the gain when it is judged that the level is stronger than a certain value. CONSTITUTION:This equipment is composed of a variable gain amplifier 1, radio frequency filter 2, first mixer 3, intermediate frequency filter 4, local oscillation filter 5, level detection part 6, attenuation selection and decision part 7 inside a control part, and selective attenuation changeover switch 8. A signal received from an antenna and a DC signal, whose frequency is converted, corresponding to the level detected by the RSSI level detection part 6 is transmitted to the control part. An RSSI output is correlated with the received signal level and when it is judged by the attenuation selection and decision part 7 that the reception input level is stronger than a certain value, the reception level is reduced by decreasing the base bias of the low noise amplifier 1 and operating the switch 8 so as to decrease the gain of the low noise amplifier 1. |
