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实现SAW滤波器低损耗化的方法之一——反射器内置型IDT的研究工作近来十分活跃。这种IDT的外电路及制作工艺简单,并且能在宽带范围内实现低损耗,因此,它极有希望用作图像和宽带数据传输用滤波器。但是,在此以前的文章中曾报道:采用此IDT制作滤波器时,由于反射寄生信号大,故在通带内会产生大的波纹。本文为解决这一问题提出了可抑制宽带内反射寄生信号的新结构形式的反射器内置型IDT——分布声反射型换能器,阐述了这种IDT的工作原理,并介绍了利用第一次近似的设计方法。结果证明:采用这种IDT可制成能将宽带内不需要的反射抑制到45dB以上、插损为10dB以下的低损耗滤波器。
One of the ways to achieve low SAW filter loss - the reflector built-in IDT research work has been very active. The IDT’s external circuitry and fabrication process are simple and provide low loss over a wide bandwidth, so it is highly promising as a filter for image and wideband data transmission. However, it has been reported in this prior article that when a filter is fabricated using this IDT, large ripples are generated in the passband due to the large reflected parasitic signals. In order to solve this problem, this dissertation proposes a new type of reflector built-in IDT-Distributed Acoustic Reflectance Transducer that can restrain the broadband reflection parasitic signals. The working principle of this IDT is described. Second approximation of the design method. The results show that: Using this IDT can be made to be able to suppress unwanted broadband reflection above 45dB, insertion loss is less than 10dB low-loss filter.