The Design And Implementation Of High Stability Frequency Synthesizer On Short-wave Transmitter

Short-wave communication for many years is widely applied to the government, the diplomatic, the military, the aviation, the weather, the business and so on, transmitting the information such as speech, letters, images and data. More than that,it is one of the most reliable methods on military command and national security sector. In recent years, countries around the world stepped up the short wave communication research, and many new short-wave communication systems have appeared. But no matter what kind of equipment, frequency synthesizers plays a core role in short-wave communication equipment. For this reason, the paper does a in-depth research on The Design and Implementation of High stability Frequency Synthesizer on short-wave transmitter.With the development of modern communication techniques, frequency synthesizer is required to have higher performance and low spurious level, pure output spectrum, fast frequency switching speed and high-resolution agile frequency synthesizer frequency synthesis technology has become the main trend of development. After comparing kinds of technique of frequency synthesizer, finally, the paper choose the DDS ASIC implementation scheme to obtain high frequency stability, low phase noise, low spurious frequency source, in order to achieve better output, it uses high stability crystal oscillator circuit for the DDS module provides the reference clock source, the design of tracking filter also is gived. The scheme is innovative and original not only in the technology but also in some module circuit.This paper introduces the topic of the research background and significance. Then introduces the synthesizer's concept, development, and discusses a PLL frequency synthesis and direct digital frequency synthesis technology and differences in their characteristics, it also has carried on the theoretical analysis to the frequency spectrum characteristic and spurious suppression characteristic. Then according to the target system, the paper reasonable chooses the direct digital frequency synthesis. The whole system takes signal generator based on DDS ASIC AD9953 as the core, single chip as controller, coupled with high stability crystal oscillator and practical tracking filter to ensure high accuracy, high frequency band range and high spectral purity. Paper a detailed analysis of the frequency synthesizer system architecture, hardware and software design and the specific circuit. Final completion of the pilot circuit board manufacture, circuit debug, the output signal spectrum was analyzed, the physical hardware, photos and test results and related analysis is proposed.