| Summary: | 碩士 === 國立成功大學 === 電機工程學系 === 89 === A novel low-loss wide bandwidth microwave SAW filter used for spread spectrum communication system has been designed and fabricated. The 16 mm input／output IDTs 128° rotated YX-cut LiNbO3 61.00 MHz SAW filter combined with microwave square open-loop resonators has an insertion loss of 3.987 dB. The same device is also a microwave microstrip filter with four coupled microstrip square open-loop resonators and two planar interdigital capacitors with S21, S11, and bandwidth of this 1 GHz novel filter being —2.962 dB, —25.497 dB, and 800 MHz, respectively. It is speculated that the characteristics of these low-loss BW=80% wide bandwidth microstrip filters are caused by the interaction between electromagnetic wave and piezoelectric surface acoustic mechanic wave. To confirm the speculations, devices with the similar design pattern have been fabricated on GaAs S-I and 9000Å SiO2／Si substrates. We find that there are indeed interactions between EM wave and SAW mechanic wave.
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