FEM Simulation

SUCCESS STORY

Huge R&D efforts worldwide are dedicated to the development of ever better performing Surface Acoustic Wave filters (SAW), to answer the fast growing demand and always tougher specifications of the Smart Phone industry. One important challenge is to achieve higher-frequency (5GHz), wide-band, low loss filters, to improve the performances of the emission/reception electronics.

Important efforts are also dedicated to the development of SAW wireless and passive sensors for harsh environment (very high temperature, corrosive atmospheres, nuclear plants…) and biomedical applications (implantable sensors).

Although SAL is already one of the world leaders in the field of SAW sensors, the Micro-acoustics development team was still in need for an advanced simulation tool to strongly improve its design and innovation capabilities whilst drastically reducing the development lead-times.

The needed tool was successfully developed over the last four years, in strong collaboration with the institute of mechanics and mechatronics of TU Vienna. A full PhD was dedicated to the development of the tool, based on proprietary FEM software (CFS++) coupled to a series of modules (semi-analytical models) developed at SAL.

More specifically, the FEM Module is able to quickly compute the properties of surface acoustic waves and bulk acoustic waves propagating within or interacting with the inter-digital transducers and reflectors that are used to generate, pick-up and reflect the acoustic waves.

As some modes can result in spurious signals that shall be eliminated to improve the signal-to-noise ratio, the computation of all these properties make it possible to accurately simulate then optimize a wide range of micro acoustic devices. The parameters obtained at the end of the FEM computation are subsequently used to compute the actual frequency or time response of a SAW device, as well as its sensitivity to temperature changes and/or deformation.

The effects of the surrounding circuitry (antenna, printed circuit board, housing…) can also be computed. It is for instance possible to simulate the response time and the sensitivity of a whole sensor when submitted to temperature changes. This makes it possible to fully optimize each of the sensors constitutive elements, for one given application.

IMPACT AND EFFECTS

Thanks to this new tool, SAL Team is now able to model, simulate and optimize a whole new range of innovative micro-acoustic devices. Especially, the tool will help develop the next generation of multi-layered SAW filters, for the mobile phone industry.

This is a challenging task, with highly promising outcomes. It will also help developing the next generation of SAL SAW sensors, for biomedical and industrial applications.

Existing SAL sensors for very high temperature will also benefit from the tool, which makes it possible to further optimize the whole circuitry/housing/sensing architecture. The main applications here are for the steel, automotive and air and space industries.