This study describes the design and fabrication of dual-mode film bulk acoustic resonator (TFBAR) devices to construct wafer level T-ladder type filters. Reactive radio-frequency (RF) magnetron sputtering method was used to deposit c-axis- tilted ZnO piezoelectric thin films. The piezoelectric ZnO thin films were deposited by a two-step method at room temperature with off-axis. In this investigation, off-axis distance was varied to determine the optimal growth parameters of the tilted piezoelectric thin film. The SEM and XRD analysis reveal that ZnO thin films deposited at off-axis distances of 35 mm yielded a highly textured and sufficiently-tilted ZnO piezoelectric layer for dual-mode TFBAR. Additionally, the ZnO piezoelectric layer with off-axis distances of 35 mm exhibited enhanced competitive growth, and had a c-axis-tilted angle of 5¢X. To explore the relationship between the c-axis-tilted angle and the dual-mode resonance frequency responses (fL and fS) of TFBAR, two TFBAR devices were fabricated with ZnO c-axis tilted at 4.4¢X and 5¢X, respectively. The TFBAR device with 5¢X-tilted ZnO layer exists shear and longitudinal resonant modes. The center-frequency of longitudinal resonant mode is 2.2 times that of the shear resonant mode. The longitudinal mode is suitable for designing as a communication receiver (Rx) device at WCDMA band. On the other hand, the shear mode of TFBAR is suitable for EGSM-900 band. To optimize the characteristics, the filter was annealed by CTA treatment in 400 ¢J. For the frequency responses of the longitudinal wave, the insertion loss was upgraded from -5.77 dB without annealing to -4.85 dB as annealed, the band rejection was reduced from 13.57 dB to 12.65 dB, the bandwidth was broaden from 69.69 MHz to 73.12 MHz. On the other hand, for the frequency responses of the shear wave, the insertion loss was upgraded from -9.94 dB to -8.21 dB, the band rejection was reduced from 13.74 dB to 13 dB, the bandwidth was decreased from 28.13 MHz to 28.12 MHz.

Bandpass microwave filters are often modeled as a set of coupled discrete and localized resonators. This model is adequate in the narrow-band case. It, however, fails to describe accurately compact structures where stray couplings can be strong. To address this problem, a new view is proposed in this thesis. Instead of basing the model on localized discrete resonances, we start by constructing a model that is based on the global resonances of the structure. These are the resonances that the ports see and emerge when the entire structure is treated as a single unit. The resulting circuit, the transversal circuit, is universal. It is valid for any coupled resonator filter. The circuit is used in optimization of compact and ultra wideband suspended stripline filters and excellent results were obtained. In order to relate the global-eigen modes model to the conventional model, the issue of representation of microwave filters is investigated in detail. It is shown that a microwave filter can be represented by an infinite number of similar coupling matrices by using different modes as basis. According to this new view, a similarity transformation in microwave coupled resonator filters is interpreted as a change of basis. Two circuits that are related by a similarity transformation represent the same filter structure by using different sets of modes as basis. These conclusions were exploited in establishing a design theory for filters with dual-mode cavities. The new theory leads to direct and accurate design techniques that need no, or minimal, optimization. No tuning is used in the CAD steps. Tuning may only be required to account for manufacturing tolerances. A new tuning configuration is described and validated by computer simulation. A novel dual-mode filter with improved quality factor and reduced sensitivity is developed and designed within the same approach. The filter is fabricated and measured and excellent results are achieved. The same design methodology was used to introduce a new class of dual-mode dual-band microwave filters with improved sensitivity. It is also shown that canonical dual-mode filters can be designed within the same view with minimal local optimization of the input cavity. / Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2010-03-31 01:33:36.818