There is an increasing demand for evaluating a component’s performance in the system environment. The performance of an antenna depends on the platform it is installed on, for example, and the antenna itself might be a system built from various RF components. The importance of the EM system simulation approach becomes obvious when considering the electromagnetic compatibility of a device. The overall performance depends on the interaction of all the components, such as PCBs, cables and housings (as illustrated by the automotive scenario shown in Figure 1).
Figure 1 3D model of a cable harness in a compact car. Small window shows cable cross sections.
However, for each of the device’s components, there might be specialized solutions that will dramatically decrease simulation time. The new CST STUDIO SUITE 2011 integrates methods to synthesize and optimally handle both the constituent components and their interaction within a complex system. In addition, the high performance computing (HPC) options enable simulation with increasing complexity, such as the example shown in Figure 2.
Figure 2 Comptation on a GPU cluster dramatically reduces simulation time for this cross.
Frequency Domain Solver with Curved Elements
With version 2011, the CST MICROWAVE STUDIO (CST MWS) frequency domain solver will feature curved tetrahedral mesh elements of high geometrical orders. In comparison to using simpler curvilinear elements (first order curved elements), which often suffer from the creation of inaccuracies in the mesh representation, higher order curved elements deliver a much smoother representation of arbitrary surfaces.
As with all mesh adaptation schemes, simulations will only converge to the correct results if mechanisms such as True Geometry Adaptation are used. These actually improve the representation of the input model continuously, rather than simply refining the first discretization of the model. The higher order curved elements will also be available for the CST MWS eigenmode solver and the fast resonant solver.
Electrically Large Structures
HPC can greatly benefit the simulation of very complex structures, like the one shown in Figure 2, but switching from standard volume methods such as FIT or FEM to surface-based integral equation or ray tracing methods is often the more efficient approach for electrically very large structures. CST MWS features an integral equation solver using the multilevel fast multipole method (MLFMM) for structure sizes of up to about 1,000 wavelengths and an asymptotic solver based on the shooting bouncing ray method for even larger structures.
Figure 3 Bistatic RCS of a destroyer at 16.9 GHz.
Both solvers can now use farfields as excitation sources. These farfields can be computed by other CST MWS solvers including the transient or frequency domain solvers. This makes the calculation of an installed antenna’s farfield possible, even for an electrically very large structure, such as the ship shown in Figure 3. CST MWS 2011 also allows the importing of more than one farfield source, thus enabling the computation of the coupling between several antennas, or of the combined farfield of multiple antennas.
For radar scattering simulations, the structure can be simultaneously illuminated by multiple sources, the properties of which can be set by means of an excitation list. This enables the simulation of arbitrarily polarized incident waves from different directions. The asymptotic solver benefits from the inclusion of surface impedance models for the simulation of coatings or seawater.
Sensitivity and Yield analysis
CST MWS transient solver provides efficient computation of broadband S-parameters and field results in one single simulation run. In version 2011, sensitivity analysis can evaluate the S-parameter dependencies on various model parameters on the basis of this single broadband simulation. Further evaluations for different model parameter sets can be derived without restarting the full-wave simulation. Hence, yield analysis for complex three dimensional (3D) models is available at virtually no additional computational cost.
The newly implemented trust region framework uses parametric models to find optimal solutions for the given goals, without rerunning expensive 3D simulations. By employing the sensitivity information provided by both of the general purpose electromagnetic solvers of CST MWS—time and frequency domain—the number of 3D simulations and, therefore, the optimization time can be cut down dramatically.
CST MPHYSICS STUDIO computes thermal and mechanical effects. While not fully integrated in the design environment, in version 2011 the temperature calculated from the electromagnetic losses can be used to change the material parameters for a consecutive electromagnetic field simulation. CST MPHYSICS STUDIO now also features a thermal solver on a tetrahedral grid.
CST STUDIO SUITE 2011 improves the integration of CST CABLE STUDIO and the CST MWS TLM solver (formerly CST MICROSTRIPES) into the CST design environment. Users interested in the analysis of radiated emissions and susceptibility will benefit from a single unified environment for all EMC related modeling tasks, including greatly simplified model set up and simulation.
In pre-processing, the definition of compact equivalent aperture models and cable harnesses can be performed in CST’s familiar design environment. Coupling between the full 3D electromagnetic field and cable solvers enables direct transient simulation of susceptibility problems in systems containing complex cable bundles, including shielded twisted pairs (see Figure 2).
Signal and Power Integrity
For high accuracy and to address layouts with non-planar elements such as wirebonds, a full 3D simulation is often necessary. CST offers import filters to layout tools of leading EDA vendors, such as Cadence®, Mentor Graphics® or Zuken. All these links open the layout in the EM design environment before setting up and running simulations.
In a major collaborative project, a link has been created that allows Cadence layout engineers to stay within their familiar environment while performing a full wave 3D extraction and EM analysis in the background. Results are back annotated to the Cadence environment, thus simplifying the engineering workflow.
CST STUDIO SUITE version 2011 is addressing the challenges of modern electromagnetic system design by tightly integrating the latest in simulation technology within an intuitive user interface. Streamlined workflows are enabling real world problems to be tackled and solved in a virtual environment, ultimately leading to an accelerated and more cost-effective design cycle.