| In recent years, with the development of wireless communication technology to high frequency, filters with smaller size, high frequency and integration are needed. Ba(Zn1/3Ta2/3)O3(BZT) ceramic which has high dielectric constant and quality factor, as well as low temperature coefficient, is favored by most science researchers. As we all know, the theory Q of BZT ceramic is14000, however, its sintering temperature is quite high which is up to1600℃, and too much ZnO volatilized during the sintering process that caused a bad influence on BZT ceramic, especially the decrease of the quality factor. With the study of related documents, through sintering higher quality factor of BZT, the BZT ceramic substrate was made. Finally, through the software ADS and micro fabrication technology, a kind of microstrip filter was made which can be used in the C waveband (4-8GHz).In this paper, the process of solid phase sintering and the methods of increase the value of Q×f were investigated, and the results proved that:(1) Pure Ba(Zn1/3Ta2/3)O3ceramic was prepared by solid phase sintering at the temperature of1600℃, and its bulk density and microwave dielectric properties were:p=7.415g/cm3, εr=29.6, Q×f=96000GHz, τf=0.5×10-6℃, respectively.(2) Ca-B-Si could effectively reduce the sintering temperature of Ba(Zn1/3Ta2/3)O3ceramic from1600℃to1150℃. But its loose structure increased the microwave loose and its quality factor dropped. When2%Ca-B-Si was doped into Ba(Zn1/3Ta2/3)O3ceramic, its microwave dielectric properties were: εr=32.06, Q×f=80000GHz, τf=-0.5×10-6/℃.(3) Low melting point compounds of MnCO3could reduce the sintering temperature of Ba(Zn1/3Ta2/3)O3ceramic from1600℃to1250℃, and prevented the ZnO volatilize. As a result of that, the quality factor increased remarkably. When1%MnCO3was doped into Ba(Zn1/3Ta2/3)O3ceramic, its microwave dielectric properties were: εr=32.78, Q×f=149000GHz, τf=-0.14×10-6/℃(4) After doping ZrO2into Ba(Zn1/3Ta2/3)O3ceramic, the sintering temperature of Ba(Zn1/3Ta2/3)O3ceramic decreased to1300℃, and its microwave dielectric properties were: εr,=34.79, Q×f=124000GHz, τf=0.31×10-6/℃.In this paper, the way of designing and fabricating microstrip filter was reseached. According to the results of the experiment, it is obviously that:when1%MnC03was doped into Ba(Zn1/3Ta2/3)O3ceramic, BZT ceramic had the best microwave dielectric properties. Therefore we prepared Ba(Zn1/3Ta2/3)O3ceramic in this way, and made it to be dielectric substrate. A four-order parallel coupled microstrip band-pass filter was designed by the simulator software ADS, then CAD layout of filter was obtained. The filter was made by microfabrication technology with designed layout. At last, S parameters of this microstrip filter were tested by vector network analyzer of Agilent E8463A. Results showed that:the center frequency of this filter was5.6GHz, and its band-pass was200MHz, the IL was less than3dB, the size was23.7×13.7mm, all its performance met miniaturization and the design target. |
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