Uhf Band Frequency Source Of Research And Design

With the development of the technology of the wireless system, more and more stable and accurate frequency synthesizers are required by the electronic system. The common frequency synthesizers may not meet the demand on frequency stability and accuracy. And some of them are just desirable at a single frequency, which only can be varied in narrower spectrum. The approach that DDS excites PLL is used to realize the more stable and accurate UHF frequency synthesizer in a proper bandwidth in this paper.At first, the PLL part and the DDS part have been explained rigidly in mathematics. Then how the phrase noise and the spur influences the circuit has been discussed in this paper. The above analysis is the basic of designing high performance frequency synthesizers. At last, how to realize the whole circuit and deal with the problems in debug is presented and explained.This research about the UHF frequency synthesizer mostly includes the following parts:1) The DDS modules include the DDS AD9852 part, the LC Band pass filter design part, the amplifier design part and LC Low pass filter part.2) The PLL modules include the design of the loop filter which is the core of PLL, LC Band pass filter design and the amplifier design.3) The controller modules of the system include the part of PC Rs-232 COM port communication with the MCU and the part of the process of controller about URAT and MCU.The whole UHF frequency synthesizer has been realized, and has met the demand on the whole. Many pictures about measurement and debug of this system have been shown. In the appendix, some relevant control program about URAT and MCU is presented.