Activities

NUMERICAL METHODS

Besides having available commercial EM software packages such as IE3D, ADS and HFSS, the group has developed its own software packages for the rigorous analysis of complex antenna geometries and objects of large electrical size, which lead to full systems of equations with hundreds of thousands of unknowns. Practical examples are finite arrays, reflectors with complex feeding structures and prefractal antennas. Special attention is put on very efficient preconditioning techniques. As an example, the left figure shows the current density distribution on a 16x16 microstrip array solved with in-house developed FIESTA-3D software.

During the last years the group has also worked in the improvement of the accuracy of the Magnetic Field Integral Equation (MFIE) for objects with edges, in the improvement of the efficiency and accuracy of the thin wire model for objects with short wires and not too thin, and in the development of new NlogN algorithms for the solution of integral equations.

The Antenna Lab has also developed the well-known GRECO code for high-frequency analysis of RCS and reflector antennas using Physical Optics (PO), Equivalent Edge Currents (EEC) with Physical Theory of Difraction (PTD) and Ray Tracing (RT) techniques. The figure above shows the multiple reflections of backscattered rays in a freighter model.

ANTENNA DESIGN

The unstoppable evolution of wireless communication devices towardsminiaturization leads to the use of very small integrated antennas, for this reason the group is focused on the small antenna design and manufacturing, IC integration substrates and in integration technologies.

Compact Multiple-Input Multiple-Output (MIMO) systems may allow significant improvements into the rate and quality of the next generation of wireless systems, on this topic, the UPC works with Matching-Decoupling Circuits, Close Antenna Coupling, Mobile Radio Channel Modeling and Space-Time Coding.

Some artificial materials behave like ideal magnetic screens. These magnetic screens allow designing antennas close to the surface of the screen (compact antenna systems). Whereas size is reduced radiation is enforced, on this topic, the UPC works on thedesign of magnetic screens using mu-negative resonators, design of compact magnetic screens (patterns printed on a substrate over a ground plane), bifrequency magnetic screens and Performance comparison between magnetic screens+dipole and patch antennas.

Recent developments in antenna array design include the design, construction, testing and integration of a 4x4 element low-loss, dual polarization microstrip array antenna. The antenna has been integrated in a radiometer operating in the 1.5 GHz band as part of the WISE field measurement campaign in the ESA SMOS mission.

Another development in antenna design include a set of multiband antennas based on fractal geometry, referred for example, to a mod-p Sierpinski gasket. This design constitute a generalization of the Sierpinski antenna but with a log-periodic behavior due to their fractal self-similarity properties.

ANTENNA MEASUREMENTS AND DIAGNOSTICS

The UPC facilities have been used in the design process and validation of the LICEF receivers of the SMOS mission. The anechoic chamber also hosted the MDPP-3 experiment in March 2005. This experiment is a demonstrator of ESA-CASA SMOS radiometer. Related to the activities described in this proposal is the group experience in antenna diagnostics.

This includes antenna testing, as well as, reconstruction of antenna field distribution in the vicinity of the antenna from measurements with the objective of performing antenna diagnostics. In the case of a phase array, this technique is useful to check the proper operation of the phase shifters, and to check the proper feeding of all array elements. The figure above shows an antenna array corresponding to a GSM base station antenna is shown in the UPC anechoic chamber for antenna measurements.

INTEGRATION OF RADIO SYSTEMS

The specific objective of the integration is the development of embedded crosslayer- wireless techniques for sensor and communications network architectures with emphasis on radio frequency aspects for low-power implementations. A main specific goal of the project is to focus the previous different research efforts towards new breakthrough miniature radio systems and innovative applications.

As the demand grows for mobile costumers for broad-band multimedia services, satellites need to become more efficient in their delivery, exploiting new technologies such as multibeam antennas an on board processing.

The EEF group has experience in design, construction, calibration and characterization of electronically controlled beam steering arrays.