Lanz Roman, Muralt Paul
Unaxis Balzers Ltd., Liechtenstein, Switzerland.
IEEE Trans Ultrason Ferroelectr Freq Control. 2005 Jun;52(6):936-46. doi: 10.1109/tuffc.2005.1504014.
Frequency shift, design, and fabrication issues have been investigated for the realization of 8 GHz bandpass filters based on AlN thin film bulk acoustic wave resonators. Fabrication includes well-textured AIN thin films on Pt (111) electrodes and SiO2/AlN Bragg gratings for the solidly mounted resonators. The chosen ladder filter design requires the tuning of the shunt resonators with respect to the series one. For this purpose, mass loading of the shunt resonators with aluminum (Al) and SiO2 were studied. Design simulations showed that the channel bandwidth can be doubled by shifting more than the difference of resonance and antiresonance frequency. Bandpass filters at 8 GHz were successfully fabricated with -5.5 dB insertion loss, -26 dB out-of-band rejection, 99 MHz (1.2%) +/- 0.2 dB channel bandwidth, and 224 MHz (2.8%) 3 dB bandwidth. The group delay variations within any 30 MHz channel inside the channel bandwidth amounts to < 0.2 ns. Comparisons with simulation calculations and single resonator characteristics show that each pi-section includes a parasitic series resistance and inductance.
为实现基于氮化铝（AlN）薄膜体声波谐振器的8GHz带通滤波器，对频移、设计和制造问题进行了研究。制造过程包括在Pt(111)电极上制备织构良好的AlN薄膜以及用于固态安装谐振器的SiO2/AlN布拉格光栅。所选的梯形滤波器设计要求对并联谐振器相对于串联谐振器进行调谐。为此，研究了用铝（Al）和SiO2对并联谐振器进行质量加载的情况。设计模拟表明，通过移动超过谐振频率和反谐振频率之差，可以使信道带宽加倍。成功制造出了8GHz带通滤波器，其插入损耗为-5.5dB，带外抑制为-26dB，信道带宽为99MHz（1.2%）±0.2dB，3dB带宽为224MHz（2.8%）。在信道带宽内任何30MHz信道内的群时延变化量<0.2ns。与模拟计算和单个谐振器特性的比较表明，每个π型节都包含一个寄生串联电阻和电感。
