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動。按這種趨勢發(fā)展下去,片上諧振器達到10GHz Q值大于10000是很有可能的。而此時材料的溫度依賴性導(dǎo)致工作頻率升高,兩相抵消,工作頻率就不受溫度的影響了。圓盤的半徑為32um,縫隙中填充的氮化物厚20nm。正如[19][37]所示,這些機械濾波器的中心頻率主要由這些相同單元的諧振器的頻率決定的。相比1個單獨諧振器而言,圓盤復(fù)合陣列的能量Q值乘積增大了,從而有效提高了振蕩器相位噪聲性能。a, “Squareextensional mode singlecrystal silicon micromechanical resonator for lowphasenoise oscillator applications,” IEEE Electron Device Lett., vol. 25, no. 4, pp. 173–175, Apr. 2004.[17] R. C. Ruby, P. Bradley, Y. Oshmyansky, A. Chien, and J. D. Larson, III, “Thin film bulk wave acoustic resonators (FBAR) for wireless applications,” in Proc. IEEE Ultrason. Symp., Atlanta, GA, 2001, pp. 813–821.[18] H. Yu, W. Pang, H. Zhang, and E. S. Kim, “Film bulk acoustic resonator at GHz with ultra low temperature coefficient of resonant frequency,” in Tech. Dig., 18th IEEE Int. MEMS Conf., Miami Beach, FL, Jan. 30–Feb. 3, 2005, pp. 28–31.[19] F. D. Bannon, III, J. R. Clark, and C. . Nguyen, “High frequency micromechanical filters,” IEEE J. SolidState Circ., vol. 35, no. 4, pp. 512–526, Apr. 2000.[20] K. Wang, . Wong, and C. . Nguyen, “VHF freefree beam highQ micromechanical resonators,” IEEE/ASME J. Microelectromech. Syst., vol. 9, no. 3, pp. 347–360, Sep. 2000.[21] M. A. Abdelmoneum, M. U. Demirci, and C. . Nguyen, “Stemless wineglassmode disk micromechanical resonators,” in Proc. 16th IEEE Int. MEMS Conf., Kyoto, Japan, Jan. 19–23, 2003, pp. 698–701.[22] J. Wang, Z. Ren, and C. . Nguyen, “ selfaligned vibrating micromechanical disk resonator,” IEEE Trans. Ultrason., Ferroelect., Freq. Contr., vol. 51, no. 12, pp. 1607–1628, Dec. 2004.[28] . Wong and C. . Nguyen, “Micromechanical mixerfilters (“mixlers”),” IEEE/ASME J. Microelectromech. Syst., vol. 13, no. 1, pp. 100–112, Feb. 2004.[29] . Li, . Lin, Z. Ren, and C. . Nguyen, “Selfswitching vibrating micromechanical filter bank,” in Proc. IEEE Joint Int. Freq. Contr./Precision Time amp。由它在1kHz出相位噪聲可以推得它的功耗僅有350uW,遠離載頻時相位噪聲僅有123和136dBc/Hz[11],而使用一個圓盤的相位噪聲為110和132dBc/Hz。表3中每個濾波器的相同本質(zhì)在于每個濾波器都是依靠等效電路來進行設(shè)計的,而這些等效電路又是由許多類似的電機械單元構(gòu)成的[19][37],這樣就能進行仿真了,就像SPICE一樣,它的特點符合廣泛的自動化電路設(shè)計環(huán)境。表3總結(jié)了幾種微機械電路,從帶通濾波器到混頻濾波器、阻抗變換機械耦合陣列和使用復(fù)合諧振器機械耦合的方式實現(xiàn)的濾波器。第二幅圖所示為絕緣體上(SOI)硅酒瓶圓盤,同樣,它也很像表1中的酒瓶圓盤,但是它是在厚的SOI硅結(jié)構(gòu)層上成形的,因此有效地增大了電極與圓盤間的容性重疊部分(類似于平行板電容的面積),從而減小了串聯(lián)動態(tài)電阻。如圖3所示,當(dāng)輸出端短路時,輸入電壓對輸出電流的轉(zhuǎn)移函數(shù)為其中表示諧振器的諧振頻率、表示它的串聯(lián)動態(tài)電阻,可以寫為圖3 表1的第四種圓盤諧振器的示意圖其中和分別表示圓盤周邊的等效質(zhì)量和剛度,表示電極和諧振器縫隙間的介電常數(shù),R和h分別是圓盤的半徑和厚度。這種設(shè)計可以在室溫下工作在片上UHF諧振器中,達到很高的頻率Q值乘積。第二幅圖所示為FF梁(FreeFree Beam),它在真空狀態(tài)下頻率高于100MHz仍然能達到很高的Q值。通過CAD,我們很容易確定諧