FM radio circuit of DA-101 chip

FM radio circuits use different radio chips, and their working principles are also slightly different. The figure shows an FM
radio circuit using the DA-101 chip. In the radio state, the socket of the earphone serves as the antenna of the FM radio circuit. The FM radio program signal received by the antenna is sent to the @ pin of U13 through the coupling capacitor
c58. This signal is a radio frequency carrier wave. High-frequency amplification, mixing, intermediate frequency amplification, frequency identification and other processing are carried out in U13, and
the audio signal is demodulated and output by the ⑤ and @ pins, and then sent to the digital decoding chip for processing. The radio circuit U13 k{JI operates Under the control of the CPU
, the Izc bus control signals (DATA, CLK) of the CPU are added to the ④ and ⑤ pins of U13 respectively. The radio power supply control
signal of Ul3 is added to the gate of VT5 by the control signal of the CPU , and is supplied to the power supply of U13 through VT5 control, thereby achieving
the purpose of controlling the radio.