The study of frequency modulation for dual-band solidly mounted resonators and filters

• Main Authors: Tong-ting Wu, 吳東庭
• Other Authors: Ying-Chung Chen
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/ba63u3

碩士 === 國立中山大學 === 電機工程學系研究所 === 95 === ABSTRAT In this thesis, we focused on the fabrication and frequency-modulation of λ/4 mode dual-band solidly mounted resonators and filters. To accomplish the Bragg reflector, the RF/DC magnetron sputtering system with dual targets is adopted to deposit alternating layers of quarter-wavelength Mo and SiO2 thin films. We tune the fabrication parameters in accordance with the AFM measurement and achieve a low roughness of 2.9nm on a nine-layer reflector. The piezoelectric layer, aluminum nitride (AlN) thin films, is deposited on the Bragg reflector by means of reactive RF magnetron sputtering. We alter the distance between substrate and target is altered to deposit AlN with various c-axis tilting angle which results in longitudinal and shear acoustic waves at the same time. Furthermore, we use mass loading effect to modulate the resonance frequency and fabricate π- ladder type filters. In various numbers of reflector layers, the optimum frequency response is obtained with return loss of -26dB, in a SMR on a 3.5 pair reflector. To investigate the relationship between longitudinal and shear resonance in different resonance frequency, we alter the c-axis tilting angle of AlN as well as various mass loading on the SMRs. Based on the experimental results, the ratio of longitudinal to shear resonance frequency remains a constant value despite various c-axis tilting angle of AlN and mass loading on the SMRs. In addition, the electromechanical coupling coefficient, Kt2, of shear resonance raises with the increase of c-axis tilting angle of AlN. Finally,we have successfully fabricated SMRs with frequency modulataion of 3,899.68 Hz-cm2/ng and π-ladder type filters with 26 MHz bandwidth.