A High Speed DDS For The Direct Synthesis Of U/V Modulated Signals

In radio communication systems,UHF and VHF occupy the core of the use of radio frequency band.The U/V band basically covers the frequency range used throughout the conventional voice communications and data communications.With the development of modern communication quality and continuously improve the equipment requirements,RF synthesis and modulation domain traditional implementation method has been gradually to highlight the disadvantages,communication system updates,meet the higher requirements.Especially in the modern society,when the radio is widely used,the anti-jamming ability of U/V communication is gradually improved.In this way,it is difficult to meet the newer and higher requirements in the realization of the traditional low frequency signal synthesis and frequency conversion in the realization and the index requirements.The above problems are mainly focused on the frequency accuracy,the stray signal,the target signal EVM,the modulation domain synthesis,the frequency conversion efficiency and so on.In this thesis,Direct Digital Synthesis(DDS)and its application in U/V band radio frequency modulation signal and frequency hopping in U/V communication system as the main body,the high requirements of applications and to achieve the relevant modern U/V communication.In this study,the high performance of the direct synthesis of the frequency of the chip as the carrier,from the functional indicators of the sophisticated,analysis of the application field,the realization of the simulation,and the direct application of the project to achieve the actual product output.In the development of the whole project,the development and Realization of the main target:1.The development of broadband,low noise U/V RF signal synthesis.The high speed integrated DAC mode DDS chip is used as the core of the system,which can be used to ensure the performance of the system.The frequency of the high coverage of the communication system is controlled by the direct synthesis.With the development of high speed DDS system used,can produce frequency at 1.75 GHz and below the frequency signal,in the development of synthesis of the signal and the quality analysis and verification in detail,in order to meet the implementation of the next step and provide a reliable basis for performance.2.Development and Realization of modulation of RF signal in U/V.In modern communication,the phase modulation of voice communication and broadband is the core of voice communication and data communication.In this high speed DDS,it mainly realizes the analog modulation of voice and the modulation of high speed broadband data transmission.The main contents are as follows: amplitude modulation(AM)modulation,frequency modulation(FM),phase modulation(BPSK),in the realization of the modulation mode,its application can be extended to more modulation,amplitude,frequency and phase based.On the basis of the realization of this research,we can extend the modulation domain.For example,there are QPSK,8PSK,QAM,etc.3.Development of high speed frequency agility in high speed DDS.The most significant characteristic of high speed DDS is to directly synthesize the relevant frequency signal based on its high speed DAC.In the realization of DAC data flow,of course,also have a very accurate grasp of the data control and implementation.In the realization of high-speed DAC,the output of the RF signal to its own comparison,can be very flexible direct output DAC point control.Of course,the result is to achieve the dream of high-speed communication system signal frequency agility.And in the high-speed DDS under the direct synthesis of DAC,the frequency of agility of course,also in the frequency of the changes between the two periods of a complete cycle,which is a great guarantee of frequency agility time.The realization of ideal frequency agility from high speed DDS.