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目前,实用的基本厚度扩张模压电滤波器工作频率的上限是10.7 MHz。这里,我们研究把工作频率提高到甚高频范围的可能性。首先研究在甚高频(VHF)范围工作的单片滤波器所需的压电陶瓷的特性。满足这些特性的材料之一是热压的 Pb(Mg_(1/3)Nb+(2/3))O_3-PbTiO_3-PbZrO_3陶瓷。接着研究了这种材料的片厚和电性能之间的关系,并指出:即使片厚为几十微米材料仍可保持滤波器工作所需的电性能。在研究研磨工艺的各种条件之后,我们得知片厚的精度在±0。2μm 以内。我们研究了在研磨加工中测量薄片电性能的方法,这就使工作频率的预测得到改进。所研制的27 MHz 和57 MHz 单片滤波器样品每节的插入损失小于1.5 db,相对带宽大于5%。文中提出了一种展宽单片滤波器带宽的方法,这些滤波器是由1×1×0.04mm~3左右的小片组成的,为了防冲击用导电胶将这些小片粘到绝缘基片上。
At present, the upper limit of practical working frequency of basic thickness expansion mold electric filter is 10.7 MHz. Here, we study the possibility of raising the operating frequency to the very high frequency range. First investigate the characteristics of piezoelectric ceramics required for monolithic filters operating in the VHF range. One of the materials that satisfies these characteristics is the hot-pressed Pb (Mg 1/3 Nb 2/3) O 3 PbTiO 3 PbZrO 3 ceramics. The relationship between the sheet thickness and the electrical properties of this material was then investigated and it was pointed out that electrical properties required for the operation of the filter can be maintained even at sheet thickness tens of micrometers. After studying the various conditions of the grinding process, we learned that the accuracy of the sheet thickness is within ± 0.2 μm. We studied the method of measuring sheet electrical properties during grinding, which resulted in improved prediction of operating frequency. The 27 MHz and 57 MHz monolithic filter samples developed have less than 1.5 db insertion loss and a relative bandwidth greater than 5%. In this paper, a method to broaden the bandwidth of monolithic filter is proposed. These filters are composed of small pieces of about 1 × 1 × 0.04mm ~ 3, and these small pieces are stuck to the insulating substrate for preventing impact by using conductive glue.