Advantages of SAW filter | disadvantages of SAW filter

This page covers advantages and disadvantages of SAW filter and its basics. It mentions benefits or advantages of SAW filter and drawbacks or disadvantages of SAW filter.

What is SAW filter?

SAW stands for Surface Acoustic Wave. These filters are fabricated on wafers. It allows electro-acoustic coupling via transducer.

SAW filter structure

The figure depicts basic structure of SAW filter. As shown it stores signal in acoustic resonators unlike conventional filter which stores energy as charge on capacitor and as current in inductors. Surface Acoustic Waves propagate in lateral direction. The shape and center frequency of the passband is determined by IDT (interdigital transducers) parameters viz. the pitch, line width and thickness. It is designed to operate upto frequencies of 2.5 GHz with optimum performance.

Following parameters are used in the selection of appropriate SAW filter for your need.
• Filter Bandwidth of operation
• Transition Bandwidth
• In Band Ripple
• Out of Band Side lobes level
• Group delay variation over pass band
• Insertion Loss
• Size and Package Type
Refer SAW filter basics >> for more information with graph.

Benefits or advantages of SAW filter

Following are the benefits or advantages of SAW filter:
➨It offers low insertion loss (< 3 dB) at lower frequency range.
➨It offers excellent rejection (>30 dB out of band) at lower frequency range.
➨It covers broad bandwidth (<100 MHz).
➨Due to their fabrication on wafers, they can be produced in large volumes at low cost.
➨Moreover it offers ultra small size (~9 mm2) for critical designs as components such as filters/duplexers of different bands can be integrated on single chip with little or no additional fabrication steps.
➨This filter structure supports flexible port configurations.
➨The filter offers good temperature stability of about 3 ppm/oC .
➨The velocity of SAW waves is 105 times less compare to EM wave velocity. SAW filter designs are used where EM wave designed are impractical to be developed.

Drawbacks or disadvantages of SAW filter

Following are the drawbacks or disadvantages of SAW filter:
➨It can not be used for greater frequencies such as above 2.5 GHz and mmwave bands. As acoustic waves exhibits degradation in selectivity at frequencies >6 GHz.
➨It handles lower RF power levels than BAW filters.
➨It has more temperature variation than BAW devices.

Also refer advantages and disadvantages of BAW filter >> type.

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