A THEMATIC REPORT ABOUT THE SAW FILTERS
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The SAW filters are widely used at home and abroad, mainly used in GPS and other fields, such as positioning bracelets, positioning modules, etc. The frequency range is from 30MHz to 3MHz. The frequency range is from 30MHz to 3.7 GHz, applicable to LTE band, ISM band, GPS and GNSS band and other bands. The products are characterized by small size, high performance, high reliability and low cost, and are used in a wide range of applications such as automotive electronics, telecom infrastructure, access points and terminals, industrial and consumer IoT, and medical applications.
The internal structure of the SAW filter can be divided into the following parts:
Piezoelectric crystal substrate: the basic structure of a SAW filter utilizes acoustic surface waves on a piezoelectric crystal substrate for signal transmission and filtering. Typical piezoelectric crystal materials are quartz, lithium tantalate, etc.
Excitation and Receiving Electrodes: There are two or more excitation and receiving electrodes on the piezoelectric crystal substrate, which are used to convert electrical signals into acoustic surface wave signals or to convert acoustic surface wave signals into electrical signals. The shape and position of the electrodes have a significant effect on the characteristics of the SAW filter.
Surface Acoustic Wave Delay Line: The acoustic surface wave delay line is the key part of the SAW filter, which consists of the acoustic surface wave transmission line on the piezoelectric crystal substrate between the excitation and receiving electrodes. The length, width and shape of this line can affect the frequency response and bandwidth of the SAW.
Circuit matching network: In order to make the input and output ports of the SAW filter match correctly with other circuits, a circuit matching network is usually added between the input and output electrodes and the SAW delay line, e.g., resonators and isolators.
In conclusion, a SAW filter is a filter that utilizes piezoelectric crystal surface acoustic wave transmission, and its internal structure consists of piezoelectric crystal substrate, excitation and receiving electrodes, SAW delay line, and circuit matching network. Different internal structures and parameter settings affect the characteristics of the SAW filter such as frequency response and bandwidth.
