1 Port SAW Resonator vs 2 Port SAW Resonator | Difference between 1 Port SAW Resonator,2 Port SAW Resonator

This page compares 1 Port SAW Resonator vs 2 Port SAW Resonator and mentions difference between 1 Port SAW Resonator and 2 Port SAW Resonator. The SAW resonator basics and types including function and definition are also described.

In SAW (Surface Acoustic Wave) devices, wave travels on the surface of piezoelectric materials. They use wafers made from quartz crystal, LiTaO3 or LiNbO3 as piezo-electric materials. Wave propagation characteristics depend on cutting angle or propagation direction. There are various types of waves in SAW devices, each one is used as per desired applications.

SAW generation

Electrical signals are transformed into surface acoustic waves with the help of piezoelectric materials. When electric field is applied, piezoelectric material changes shape i.e. gets deformed.

Hence by forming comb shaped electrodes known as IDT (Inter Digital Transducers) and with signal application, SAW waves are generated. This is shown in the figure-1. The velocity of acoustic wave usually depends on substrate type or wave type (rayleigh wave, leaky wave, love wave) used. The variation in pitch of IDT electrodes will change frequency of generated waves.

In the similar way, If pitch of IDT and SAWs matches, it generates electrical signal between IDT electrodes upon application of SAW waves at the IDT.

SAW reflection

There are two basic components used in SAW devices which IDTs and gratings. To reflect SAW with wavelength "λ", pitch of λ/2 is used between electrodes as shown in the figure-2.

What is Resonator?

Definition of resonator: The device which naturally oscillates (or resonates) at some frequency with higher magnitude is known as resonator. The frequency at which maximum amplitude is obtained is known as resonant frequency or resonance frequency. The oscillations can be either EM (electro-magnetic) or acoustic in nature.

Function: The resonator is used to generate wave at specific frequency or to select particular frequencies from signal. The resonator which uses structure as shown in the figure-3 or figure-4 is known as SAW resonator.

In SAW devices, resonance is achieved by placement of grating at propagation direction of SAW which is excited by IDT.

1 Port SAW Resonator

1 port SAW resonator

The figure-3 depicts 1 port SAW resonator. It uses one IDT structure as shown.

2 Port SAW Resonator

2 port SAW resonator

The figure-4 depicts 2 port SAW resonator. It uses two IDTs, one for input and the other for output between the gratings. The 2-port SAW resonator is used as filter due to its propagation characteristics between IDTs.

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