| Frequency synthesizer plays a much more important role in the modern electric equipments with the rapid development of the modern science technology, it is a very important element to the electric system, and it has a very comprehensive application in the electric combat field covered communication, digital TV, GPS, radar, aerospace, navigation and electronic warfare. Direct digital frequency synthesis technology has been more and more concerned as the advanced frequency synthesis technique with the industrial art and the improved technology skills.This subject adopts the direct frequency synthesis technology as the key of signal generator, it proposals the meaning and purpose of the subject chosen by analyzing the background and situation of the current frequency synthesis technology. It analyzes the frequency synthesis technology specifically including its mathematics principle, performance characteristic and the chip of direct digital frequency synthesis technology.And then it builds the design model of the whole system at the same time with the analyzation. The system is made of 5 modules, which are power module, SCM module, DDS module, USB communication module and Man-Machine modules separately. The chips chosen are PIC16F876A of Microchip, DDS with AD9850, USB communication chip with FT232BM etc. SCM will realize the data process and communicate with upper computer. At the same time, it completes the hardware circuit diagram and software program of the whole system including the software design of upper and downer computer. Consequently, it finishes the circuit with the components. Finally, it makes a debug both with the software and hardware, and also make a measurement and analysis to the system.The measured results show that the signal generator output frequency range is 0-4MHZ, a wider frequency range, high frequency resolution with frequency sweep function, which supports USB control, reliable and stable with a high application value. |
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