SAW filters are electronic filters that are designed and manufactured using surface acoustic wave (SAW) technology. SAW technology uses piezoelectric transducers that, when excited, produce waves that are used to filter frequencies. Surface acoustic wave filters that operate in gigahertz (GHz) range are used widely in mobile communication systems. SAW filters are also used in radio frequency (RF) modems, alarm systems, wireless remote controls, satellite receivers, video transmission fields, telemetry systems, and mobile phone applications. SAW filter manufacturers differ in terms of capabilities and conform to a variety of regulatory requirements and quality standards.
Types of SAW Filters
There are many different types of SAW filters. Examples include IF SAW filters, CDMA SAW filters, wideband SAW filters, and piezoelectric SAW filters. An IF SAW filter uses an intermediate frequency (IF) and suitable for many third-generation (3G) base station equipment protocols. A CDMA SAW filter is based on code division multiple access (CDMA) technology. CDMA SAW filters are used in mobile phones which operate in the frequency band of 800 MHz and 1.9 GHz. A wideband SAW filter is a high-frequency filter that is capable of providing high stability. A piezoelectric SAW filter consists of two inter-digital transducers (which are mounted on a piezoelectric substrate. Other SAW filters are commonly available.
Selecting SAW Filters
Selecting SAW filters requires an analysis of specifications and features. A typical SAW filter can usually operate over a frequency range from 50 MHz to 2 GHz. With an IF SAW filter, performance specifications include insertion loss (dB), output impedances (ohms), and input VGA (ohms). A wideband SAW filter is also be specified in terms of insertion loss and impedance. In terms of features, a wideband SAW filter provides high stop-band attenuation. A piezoelectric SAW filter that is based on lithium tantalate (LiTaO3) provides high stability and good performance. Other types of SAW filters may carry different product specifications.