Requirements for SAW filters for High End Telecommunications: Flat pass band Low insertion loss Low amplitude, phase and group delay ripple Sharp filter characteristics and excellent close-in rejection Specified absolute group delay Custom shaping of filter passband and transition band

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SAW filters for Telecommunications
There are various different design principles which are suitable for the design of SAW filters for telecommunications. However, none of them meets the requirements perfectly. Precision filter design meets most of the requirements such as low amplitude, group delay and phase ripple in combination with high close-in rejection and outstanding selectivity. The high insertion loss is a disadvantage.
Low insertion loss and/or miniaturized package size are usually covered by more resonant design principles.

Design capabilities
Precision filters are based on transversal filter design principles. For precision filters, a high level of accuracy in simulation has been achieved. Here, most second order effects are implemented in the simulation model (e. g. the charge distribution shown above). For precision filter designs the shaping in transition band can be specified together with the pass band and stop band. In addition, this is the only SAW filter design principle for which amplitude and phase/group delay can be chosen independently.

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Filter layout, meshing and charge distribution: In IDTs, charge distribution is not a constant. For the design of precision filters with apodised transducers it is therefore essential to consider charge distribution one of the most important second order effects.

VI-Telefilter products for Telecommunications
VI-Telefilter’s strategy is to provide continued support for the lifetime of the products, although 75% of the products for telecommunications are no older than 2 years.
The wide range of IF and RF SAW filters take advantage of a large selection of quartz, lithium niobate and lithium tantalate substrate material cuts. This allows for optimal performance of narrow band, medium band and wide band filters.
VI-Telefilter leads the market for GSM base station filters.

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Telecommunications and VI-Telefilter
All VI-Telefilter plants are TS16949 and ISO14000 certified.
VI-Telefilter has several production lines that enable us to address low-volume, medium-volume and high-volume markets. Multilayer ceramic-based, surface-mount and metal-can pinned solutions are supported.
Many different SAW design principles are available for customized solutions.
VI-Telefilter provides filter sets and cascaded filter pairs.
Customized solutions may include an internal matching of the filter to 50 Ohms. Filters for ovened applications are available.

"Vectron International-Telefilter is our supplier of SAW filters for GSM/UMTS repeaters. For SAW filters we need technical solutions that fully meet our specifications. VI-Telefilter has proven both to have the design necessary expertise, and to be very flexible. Over the past few years, VI-Telefilter has become our reliable partner for reasonably priced high-quality components what has qualified them to be among our single-source suppliers."
Udo Krause, Procurement Manager, Wireless Innovation Group, Mikom GmbH – An Andrew Company