Section: Software
PRESTOHF
Participant : Fabien Seyfert.
PRESTOHF: a toolbox dedicated to lowpass parameter identification for microwave filters http://wwwsop.inria.fr/apics/personnel/Fabien.Seyfert/Presto_web_page/presto_pres.html . In order to allow the industrial transfer of our methods, a Matlabbased toolbox has been developed, dedicated to the problem of identification of lowpass microwave filter parameters. It allows one to run the following algorithmic steps, either individually or in a single shot:

determination of delay components, that are caused by the access devices (automatic reference plane adjustment),

automatic determination of an analytic completion, bounded in modulus for each channel,

rational approximation of fixed McMillan degree,

determination of a constrained realization.
For the matrixvalued rational approximation step, PrestoHF relies either on hyperion (Unix or Linux only) or RARL2 (platform independent), two rational approximation engines developed within the team. Constrained realizations are computed by the RGC software. As a toolbox, PrestoHF has a modular structure, which allows one for example to include some building blocks in an already existing software.
The delay compensation algorithm is based on the following strong assumption: far off the passband, one can reasonably expect a good approximation of the rational components of S_{11} and S_{22} by the first few terms of their Taylor expansion at infinity, a small degree polynomial in 1/s . Using this idea, a sequence of quadratic convex optimization problems are solved, in order to obtain appropriate compensations. In order to check the previous assumption, one has to measure the filter on a larger band, typically three times the pass band.
This toolbox is currently used by Thales Alenia Space in Toulouse and a license agreement has been recently negotiated with Thales airborne systems. XLim (University of Limoges) is a heavy user of PrestoHF among the academic filtering community and some free license agreements are currently being considered with the microwave department of the University of Erlangen (Germany) and the Royal Military College (Kingston, Canada).