DM588 Service Manual
4.4.Frequency Synthesis Circuit
The frequency synthesis circuit is composed of the phase-locked loop (PLL) chip LMX2571, a loop
filter (LPF), a voltage-controlled oscillator (VCO) and a feedback network. To the LMX2571, a work
clock is provided by the active resonator U9 and configuration data is provided by the master chip
LT1901. The LPF consists of a 4-stage resistor-capacitor (RC) filter circuit. The TX VCO and the RX
VCO respectively includes a varicap, an inductor, a capacitor and a transistor. The feedback network
consists of an inductor and a capacitor. After frequency synthesis, the TXLO signals and RXLO
signals are generated and sent respectively to the transmitting circuit and the receiving mixing circuit.
The modulated signals MODE1 and MODE2 are modulated respectively by the active resonator U9
and the TX VCO.
4.5.Power Supply Circuit
6
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