Design And Implementation Of The1.5GHz Wideband Variable Local Oscillator System

Frequency synthesizers are essential and key parts in many modern electronic systems, whichdetermine their performances. With the rapid development of modern military, national defence andwireless communication technology, many electronic systems such as radar, mobile communications,electronic measurement instruments, electronic countermeasures etc. put forward higher and higherrequests on frequency synthesizers.Wideband,low spurious,faster frequency agility,high frequencyresolution frequency synthesizers has been becoming hot spot in recent years.Firstly, this thesis briefly introduces some basic frequency synthesis technique, with theiradvantages and disadvantages, several common mixing frequency synthesis programs have beendiscussed. Based on the expected specifications of the project,a realization method of wideband,lowspurious,high frequency resolution frequency synthesizer and its key technologies are presented.During the research of frequency synthesizer, the key technologies of programmable low spurious fastfrequency synthesizer based on cascaded DDS are researched and analysed. Two DDS device are usedto realize the wide frequency range of frequency adjustable frequency synthesizer, reduced thespurious output level of the system. A extended frequency component is composed of three-levelfrequency doubler and power amplifier hardware electric circuit is designed, realized the bandbroadening and up-conversion， completed the4to5.6GHz wideband, low spurious frequencysynthesizer.The test results show that the programmable low spurious fast frequency synthesizer based oncascaded DDS has realized within the range of50to250MHz, the spurious suppression is superior to-50dBc. The output power of eight multiplier is0dBm with±3dB power fluctuation, the suppressionof harmonic greater than44dB, phase noise is-70dBc/Hz@10KHz. Therefore, the feasibility hasbeen proved and the goal of this project is basically accomplished. In this thesis, a series ofmeaningful work, some valuable results with wideband and low spurious frequency synthesizer aremade, including simulation and realization of the circuit, which provides references for the furtherrelative research of frequency source.