Cendes, Z.
Ansoft Corporation, UNITED STATES
Electromagnetic field simulation has long been transformin
g the way antenna engineers work. Twenty years ago, antenna design was primarily a cut-and-try endeavor that relied heavily on hardware prototypes and measurements to achieve performance objectives. Ten years ago, only single elements or small collections of elements could be simulated using finite element or method-of-moments field solvers. Today, new developments in field solver technology enable much larger simulations and more comprehensive design and optimization which include not only the antenna but also the platform or environment within which the antenna operates. This talk will describe the current state-of-the-art in electromagnetic field simulation and project future directions in this area.
Key new developments that enable the simulation of complex antenna systems are:
The design flow for a phased array antenna system will be examined first. That flow includes aperture element design using periodic boundary conditions that simulate an element within an infinite array. Active element patterns will be computed and shown. The element matching network design will be shown using circuit simulation and optimization. Considerations for array feed network design will be discussed with application of circuit/electromagnetic co-design. The effects of the edges of a finite-sized array will be solved and the radiation of such an array will be computed. Periodic boundary conditions will again be exploited to allow radome/FSS design. Finally the array will be placed within the radome to evaluate array/radome interaction and radiation performance.
Portable handset design will also be considered by following a flow that includes element design trades (balanced vs. unbalanced) and single element radiation analysis. Application of electronic bandgap materials to create a specialized groundplane to reduce backlobe radiation will be examined and calculation of the specific absorption rate with and without the groundplane will be presented. Antenna performance in the presence of a human body will be computed. Finally, the entire antenna plus human operator antenna system will be placed within a full-scale automobile and radiation performance will be evaluated.
The future of electromagnetic design is emerging. The seeds of the future are evident in current trends.
Christodoulou, C.
University of New Mexico, UNITED STATES
Re-configurable antennas, with the ability to radiate more than one pattern, at different frequencies, are necessary in radar and modern telecommunication systems. The requirements for increased functionality, such as direction finding, radar, control and command, within a confined volume, place a greater burden in today's transmitting and receiving systems. A solution to this problem is the re-configurable antenna
By combining low-loss, high-isolation RF MEMS switches with compatible antenna elements, we can physically reconfigure antennas and their feed structures providing frequency band and polarization diversity. RF MEMS or other switches are used to alternately connect or isolate sub-structures on a planar antenna element, creating a geometrically distinct radiator for each combination of switch positions. In this work, several plane reconfigurable antenna structures are presented and discussed.
The antennas to be presented cover a wide range of designs such as fractal antennas, triangular antennas, dipoles and monopoles. The presence of the switches themselves can have an adverse effect on the performance of the antenna. Some of the challenges that the designer has to face in biasing and integrating these switches with the antenna are also presented and discussed.
The figure below depicts the layout of a cactus-like shape reconfigurable antenna. In this case we use a monopole antenna with sleeves on its sides. Both the main monopole part and the sleeves have extensions that can be connected through MEMS switches or PIN switches to create a frequency agile antenna.
