Requirements for SAW filters for WiMAX Applications: RF and IF filters requested Low insertion loss and sharp transition from passband to stopband for IF filters (bandwidth from 3.15 to 13.2 MHz) Low insertion loss and high input power handling capabilities for RF filters Low cost

· WiMAX Brochure (245 K)

SAW filters for WiMAX Applications
IEF (Impedance Element Filters) constitute the basic design principle for RF filters. SPUDT (Single Phase Unidirectional Transducer) and SFIT (Slanted Finger Interdigital Transducer) are normally used for IF filters. Quartz and LiTaO3 are substrate materials to handle a wide bandwidth range with a low insertion loss.

Design capabilities
IEF are oneport resonators used as impedance elements.
Resonators are arranged in a ladder configuration. The difference between the acoustic impedance of resonance and anti-resonance is used. The resonators may be designed to have different resonant frequencies.
If resonators are designed in a way that the resonance of the serial arm and the anti-resonance of the parallel arm coincide, a band pass characteristic is obtained. A well-optimised filter offers a very low pass band loss and high close-in rejection.
A high capacitive coupling in the serial arm allows handling a high input power in comparison with other low-loss SAW design principles.

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High capacitive coupling in serial path allows handling of high input power in comparison to other low loss SAW design principles.

VI-Telefilter products for WiMax
VI-Telefilter offers RF filters and IF filters for several regions of the world. Concerning RF filters, the latest decisions of the FCC to define TX and RX bands in the US have been supported (TFS2535 and TFS2657). Other filters following the WCA proposal are available as well.
Concerning IF filters, VI-Telefilter adheres to standards for Europe, the USA, and the rest of the world, which has resulted in the development of low-loss filters with a bandwidth of 3.15 to 13.2 MHz.

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VI-Telefilter’s competence
All VI-Telefilter plants are TS16949 and ISO14000 certified.
In our factory in Neuchatel (Switzerland), we support all processes down to a linewidth of 0.35 µm (3 GHz) necessary to produce RF SAW filters.
VI-Telefilter is using its experience in the development and production of low cost IF filters for WLAN applications and the field of GSM base station filters, where VI-Telefilter takes a leading position to support the upcoming market for WiMAX applications.