SAW vs. BAW: How the Delay Line Technologies Stack Up

by Jaymie Murray 8. June 2015 08:11

SAW (Surface Acoustic Wave) and BAW (Bulk Acoustic Wave) technologies are widely used in a variety of applications, including filters, oscillators, transformers, and delay lines. SAW and BAW delay lines in particular offer several advantages over other signal wave technologies and are used in a variety of applications, from Electronic Warfare (EW) target generation to communications systems for television and video. While they are used in somewhat similar applications, SAW and BAW technologies are each unique and have distinctive characteristics. Factors such as required signal delay, frequency, footprint, and cost all must be considered when choosing the best delay line solution for a project. 

Both SAW and BAW devices exploit the piezoelectric effect of certain substrate materials such as quartz and lanthanum gallium silicate by using interdigital transducers (IDTs) to convert acoustic waves to electrical signals and vice versa. Delay lines that utilize SAW and BAW are designed to introduce a calculated delay into the transmission of a wave signal. This signal delay could be needed for a variety of reasons. For example, in weather Doppler systems, weather radars emit pulses which track the movement and location of objects such as hailstones and raindrops. BAW delay lines are used to control the timing of these pulses. SAW delay lines provide required delays to synchronize data in communications systems such as television broadcasting. 

In each of these examples, one technology is the best choice over another because of their respective characteristics. SAW delay lines are usually smaller and lighter than BAW delay lines, which gives them a smaller footprint and therefore can make them less expensive. SAW delay lines also typically offer a wide frequency range from 30 to 2000 MHz. However, SAW delay lines can only provide a fairly small delay range of 0.1 to 10 µsec. If a larger delay range is needed, then BAW delay lines, with a typical range of 0.15 to 3000 µsec, are the best option. This can translate into a larger footprint and raise costs somewhat, but the wider delay range allows for increased adaptability and flexibility.  BAW can also be safely used in a wider temperature range than devices that use SAW, making it a more appropriate choice for harsh or extreme conditions. 

While they are both equally reliable and can offer the delays needed for effective wave signal processing, SAW and BAW each have their own distinct advantages. Ultimately, the best delay line option will be the one that most closely meets important project requirements, such as footprint, frequency, cost, and delay time. 

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This post originally appeared in Wireless Design & Development

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