Research And Design Of Frequency Hopping Synthesizer Based On DDS

FH (Frequency Hopping) has many benefits such as good security, stronganti-jamming and CDMA network building, and etc. Thereby it shows more andmore advantages in military and civil utilization. Frequency synthesizer is one ofthe key technologies for building frequency-hopping communications system.And it has a decisive impact on the performance. Therefore, the study andimplementation of FH frequency synthesizer is very important.In this paper, first, the basic theory and characteristics of spread spectrumcommunications was introduced. The basic model and gain of the spreadspectrum communication system was studied. Then, after focusing on the study ofthe frequency synthesizer technology, the advantages and shortcomings ofdifferent frequency synthesizer scheme were introduced and the suitablefrequency synthesizer scheme was chosen. On this basis, this paper choose a newhigh clock DDS chip named AD9850 from ADI company to implement directdigital frequency synthesizer, singlechip AT89C52 implement the control circuit.Then the design of PCB board and some proceeding attention were introduced.At the end, the testing of frequency synthesizer was completed, such aslinearity, set up time of frequency, output wave and the waste electricity offrequency synthesizer. The result of testing show that all index of frequencysynthesizer were satisfied design request. The frequency synthesizer implementsthe FH well.