In the past few years a new class of SAW devices has been under development based on the use of one port SAW resonators as lumped elements with their impedance strongly changing in a frequency range of effective SAW excitation. These 'SAW impedance elements' can be connected in ladder type, balanced bridge type, or others types of networks to provide desired filter characteristics. In this paper the admittance characteristics of a single element are analyzed using coupling of mode (COM) model simulations. It is found that resonant type characteristics of a long transducer can be described by very simple formulas. The frequency gap between resonance and anti-resonance, important for filter design, is determined practically by the /spl Delta/V/V parameter of the piezoelectric substrate used, while the minimum magnitude of the impedance at the resonant frequency is determined by the SAW attenuation. The internal reflections only shift the resonance to the left edge of the stopband not changing other characteristics. A case of a synchronous resonator comprising a relatively short transducer and two reflectors placed on both sides of it is also analyzed. This type of impedance element has smaller frequency shift between resonance and anti-resonance points.
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机译：在过去的几年中，基于使用一个端口的SAW谐振器作为集总元件，正在开发一种新型的SAW器件，其阻抗在有效SAW激励的频率范围内会发生很大变化。这些“ SAW阻抗元件”可以梯形，平衡电桥或其他类型的网络连接，以提供所需的滤波器特性。在本文中，使用模式（COM）模型模拟耦合来分析单个元素的导纳特性。发现可以通过非常简单的公式来描述长换能器的谐振型特性。谐振和反谐振之间的频率间隙（对于滤波器设计很重要）实际上是由所用压电基板的/ spl Delta / V / V参数确定的，而谐振频率处的阻抗的最小幅度由SAW确定衰减。内部反射仅将谐振移至阻带的左边缘，而不会改变其他特性。还分析了同步谐振器的情况，该谐振器包括相对较短的换能器和两个放置在其两侧的反射器。这种类型的阻抗元件在共振点和反共振点之间具有较小的频移。
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