He Xiangyu, Lu Jiaqi, Gao Feng, Dong Shurong, Li Juan, Jin Hao, Luo Jikui
College of Information Science & Electronic Engineering, Zhejiang University, Hangzhou 310027, China.
ZJU-Hangzhou Global Scientific and Technological Innovation Center, Zhejiang University, Hangzhou 310027, China.
Polymers (Basel). 2024 Jan 3;16(1):150. doi: 10.3390/polym16010150.
Poly(vinylidene fluoride-trifluorethylene) (P(VDF-TrFE)) has promising potential applications in radio-frequency filters due to their excellent piezoelectric properties, flexibility, and stability. In this paper, a flexible film bulk acoustic wave filter is investigated based on P(VDF-TrFE) as piezoelectric film. A new method based on three-step annealing is developed to efficiently remove the porosity inside the P(VDF-TrFE) films so as to improve its properties. The obtained film achieved high β-phase content beyond 80% and a high piezoelectric coefficient of 27.75 pm/V. Based on the low porosity β-phase films, a flexible wide-band RF filter is designed, which consists of a bulk acoustic wave resonator and lumped inductor-capacitor elements as a hybrid configuration. The resonator sets the filter's center frequency, while the lumped LC-based matching network extends the bandwidth and enhances out-of-band rejection. The testing results of the proposed wide-band filter show its good performance, with 12.5% fractional bandwidth and an insertion loss of 3.1 dB. To verify the possibility of folding and stacking the flexible bulk acoustic wave devices for high-density multi-filter integration in MIMO communication, bending tests of the filter are also conducted with the bending strain range up to 5500 με. The testing results show no noticeable performance degradation after four bending cycles. This work demonstrates the potential of β-phase P(VDF-TrFE) bulk acoustic wave filters to expand the scope of future flexible radio-frequency filter applications.
聚偏氟乙烯-三氟乙烯（P(VDF-TrFE)）因其优异的压电性能、柔韧性和稳定性，在射频滤波器方面具有广阔的潜在应用前景。本文研究了一种基于P(VDF-TrFE)压电薄膜的柔性薄膜体声波滤波器。开发了一种基于三步退火的新方法，以有效去除P(VDF-TrFE)薄膜内部的孔隙率，从而改善其性能。所制备的薄膜实现了超过80%的高β相含量和27.75 pm/V的高压电系数。基于低孔隙率的β相薄膜，设计了一种柔性宽带射频滤波器，它由一个体声波谐振器和集总电感-电容元件组成混合结构。谐振器设定滤波器的中心频率，而基于集总LC的匹配网络扩展带宽并增强带外抑制。所提出的宽带滤波器的测试结果显示出其良好的性能，分数带宽为12.5%，插入损耗为3.1 dB。为了验证在MIMO通信中折叠和堆叠柔性体声波器件以实现高密度多滤波器集成的可能性，还对滤波器进行了弯曲测试，弯曲应变范围高达5500 με。测试结果表明，经过四个弯曲周期后，性能没有明显下降。这项工作证明了β相P(VDF-TrFE)体声波滤波器在扩大未来柔性射频滤波器应用范围方面的潜力。
