| Summary: | 碩士 === 國立成功大學 === 電機工程學系 === 85 ===
Today, Mobile telephone services are provided in various countries in the world. The mobile telephone equipment has made a great progress in achieving compactness and low power consumption to which the development of VLSI circuits. Other components which have grealty contributed to the above are filters and duplexers which are the key components of these equipment. Filters and duplexers very compact in size and very small insertion loss have become avaiable.
In this thesis, the microwve filters and duplexers provide low insertion loss, good temperature stability and compact in size because the ceramics material of BSST system in high dielectric constant and high Q value was chosen in the fabrication. The filters comprise several stages of 1/4-coaxial dielectric resonators supporting the propagation of TEM mode, and the resonators are short-circuited at one end and open-circuited at the other end. According to the coupling type, the filter can be divided:
(1)direct-coupled filter: The frequency response of the filter can be controlled by adjusting the coupling apertures between adjacent resonators.
(2)comb-line coupling filter: We can get the frequency response of band-pass filter by depositing electrode patterning of different size on the open-circuited end. By this coupling method, we can make the filters into one block of ceramics body, reduce the volume and the cost of the filters.
The duplexer was composed of two mono-block filters of different center frequency, one of which is tuned to the transmitting filter and the other to the receiving filter. We reduce the cross modulation distortion by insertion attenuation pole into the filter and spreading the attenuation pole over the passband of the opposite bandpass filter. The performance of the duplexer shows a 20dB/25MHz shape factor between the transmitter filter and receiver filter. The volume of this duplexer is less than 1.3 cm3.
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