On The Design Of Digital Synthesizer Based On Phase-Locked Loop

The frequency synthesizer is the key parts of scientific research, teaching experiment andelectronic measurement technology. With the rapid development of communicationtechnology, high accuracy measurements increasingly require higher stability, accuracy andresolution of the signal source. This makes the frequency synthesizer more important. Itproduces a large number of reference signal and discrete signal source with the sameprecision and stability, local oscillation signal to provide reference for the frequencyconversion. All influence the frequency synthesizer design, performance of wirelesscommunication transceiver costs, so the design of an ideal frequency synthesizer is moreimportant. Modern frequency synthesis technology is developing towards high performance,miniaturization. The focus of this paper is to be set to achieve the design of PLL frequencysynthesizer.The thesis designed a kind of synthesizer suit to radar system. This synthesizer generallyhas tougher requirements on noise and spurious signal than other types. It selected thesynthesizer based on PLL after the comparison and analysis of different alternatives. Throughtheoretical analysis and the thought of modularization design, it derived the system transferfunction, figured out the parameters of concrete circuit, and finally designed the circuitconforms to design requirements.It uses large-scale integrated PLL synthesizer145152-2as the core device, and thefollowing design to form the whole circuit of phase-lock frequency synthesizer. High speeddual mode frequency demultiplication MC12017as the preposition frequency divider forfeedback circuit, integrated voltage-controlled oscillator MC1648as the output module forcircuit, and integrated operational amplifier LM358as the low-pass filter for loop circuit. Ituses MCU to automatic control the prescalers, and LED to display. This circuit has simplestructure and low cost.Through the debugging and testing of the system, the results show that the frequencyresolution of the system is higher, the frequency range of distribution is relatively wide, theoutput signal spectrum purity, intelligent control, high cost performance, and has goodapplication prospects.