| YIG Tuned Filter (YTF) plays a vital role in various systems such as ecm, radar,communication, nevigation, measure-and-control and microwave test equipments, dueto its high performances such as successive tuning in wide band of multi-octave, deepout-band suppression and good tuning linearity. As the preselector of receiver, YIGband-pass filter can trace, search, select, analyze and identify signals by workingtogether with controlling and dealing units, while YIG band-reject filter can preventinterference and protect system by obstructing useless signals.For years, YTF technologies were deeply researched in aspects of material, circuitdesigning and producing process, and achieved a high level, but its inherentcharacteristics, nonideal tuning linearity and temperature drift, for instance, still existand bring disadvantageous effect to the frequency precision in applications. The manualcompensating method adopted now for YTF components consumes considerableamount of labor and time, and its inefficiency can not meet the need of mass production.On the other side, along with the rapid development of computer technology, thestandardization of commands for programmable instruments and the unification ofcommunication interfaces, various automatic test systems based on computer andcomposed of general-purpose test instruments are gradually widely used in applications.The users can write their own softwares for special test purposes according to needs.So, an automatic compensating system is designed for tuning linearity andtemperature drift of cnc YTF components in this project, for the sake of improving theefficiency of mass production of YTF components.As to the nonideal tuning linearity and temperature drift of YTF, this articledoesn’t discuss the optimization of YTF itself, but begins with the relationship betweendriving data and working frequency, and brings forward a way to compensate bymodifying the driving data. The signal transformation of the cnc YTF component isanalyzed, and the unique relation which has nothing to do with hardware parameters isutilized as the breakthrough in the numerical compensation. So, a conclusion is educedthat the compensating method is the way of modifying the driving data to proper values. Then, two numerical compensating methods, curve-drafting and direct-modifying, arediscussed and compared, and finally the direct-modifying is selected as the basicmethod of the automatic compensating system.The automatic compensating system is composed of computer, vector networkanalyzer, high-and-low temperature test chamber and the cnc YTF component. Thedesigning work mainly includes the following aspects.1) Design of communication interfaces of the systemThe communication interfaces involve hardware and software. The hardwareinterfaces include GPIB, RS232and RS485, and the software interfaces include SCPI,self-defined commands, etc.2) Design of cnc driver for YTF component, including hardware and softwareThe driver is based on MCU whose type name is ADuC831. It can work in threemodes, compensating mode, data-downloading mode and normal-working mode, and itis properbly designed for every stage of the producing process of YTF components.3) Design of the compensating software that works in computer systemThe software can be divided into several functional parts, including parametersettings, compensating process controlling, data downloading, etc.As the core of the automatic compensating system, the computer software controlsthe vector network analyzer, the temperature test chamber and the YTF component,and makes them cooperate with each other to accomplish the compensation offrequency precision in normal, high and low temperature environments. With theautomatic compensating system, the needed time is reduced to less than15%of themanual operation, and the efficiency of YTF mass production is enormously increased.By the mean time, it also contributes to the coherence of products due to the formalityof the computer programmed operation. |
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