SELECTIVE RADIO CALL RECEIVER

摘要

PURPOSE:To automatically adjust an antenna tuning section to the best state in accordance with a receiving frequency by detecting the level of a radio call signal on the poststage side of the antenna tuning section and deciding the control signal to be given to the element of the antenna tuning section so that the level of the radio call signal can become the highest. CONSTITUTION:A series circuit composed of a fixed capacitor 201 and variable- capacity capacitor 203 is connected between one end of an antenna 1 and ground and a fixed capacitor 202 is connected between the other end of the antenna 1 and the input of a radio section 3. An antenna tuning section 2 is constituted by connecting a parallel circuit of three variable-capacity capacitors 204-206 between the connecting point of the capacitor 202 and antenna 1 and ground. When antenna tuning is not obtained against a receiving frequency, the output level of the section 3 becomes lower. In such a state, an output controlling section 16 adjusts the voltage applied across varactor diodes 203-206 by controlling transfer gates 109-113 so that the best tuned point can be obtained against the receiving frequency.