XFdtd Release 7.4.0

PrOGrid Project Optimized Gridding™

New capability in the gridding algorithm allows users to create grids that conform to best practices and guidelines. While the underlying gridding algorithm remains unchanged, PrOGrid's new controls in the main grid editor and part gridding properties enable users to efficiently optimize the trade-off between accuracy and runtime.

Users can control the following aspects of gridding:

• Finer resolution around conductor edges where fields are strongest.
• Minimum number of cells across features, e.g., microstrips and substrates.
• Smaller cells inside dielectrics where the wavelength is shorter.
• Free space padding that is determined based on a fraction of a wavelength.

Poseable Hand

XF can mimic the numerous grips used to hold mobile devices when users import Poseable Hands from CADHuman and reposition them using controls at each joint in the fingers and thumbs. Users can also align the imported models with other parts in the project, making it easy to grip a device with the imported hand.

Customers who wish to use this capability can purchase the Poseable Hand models directly from CADHuman.

Biological Thermal Solver

XF's enhanced thermal sensor allows users to include metals and other non-biological objects in the temperature rise computation. The calculations are based on Pennes' bioheat equation and consider the effects of conductive heat transfer between thermally connected materials, blood perfusion, metabolic processes, and general radio frequency (RF) heating.

The new sensor is well-suited for analyses related to the following topics:

• Therapeutic heating devices.
• MRI heating in patients, including effects of implants, probes, and electrodes.
• Microwave thermal ablation.
• Implantable devices.

MATLAB Export

The export includes the following highlights:

• E, H, B, and J fields for point, planar, and volumetric sensors.
• Rotating B+/- and specific absorption rate (SAR) results.
• Grid vertex locations and mesh material properties needed for custom SAR post-processing.

Cropped 3-D Mesh

STL Import

Dispersive Material Calculator

XF provides a dispersive material calculator that fits a single-pole, frequency-dependent, Debye-Drude material to a set of material data points over a frequency range.

Users can input data points in the following ways:

• Sampled data: based on measurements of a material taken at multiple frequencies.
• Constant loss tangent: a constant relative permittivity and loss tangent over a frequency range.

Picking Geometry Edges and Vertices

This release offers additional choices for connecting the picker tools to specific edges or vertices rather than selecting geometry faces. These restrictions allow users to easily choose an exact edge or vertex when using the picker tools for placing components, specifying orientation, or attaching waveguide interfaces.

Users can explicitly direct the picker tools using the following keys:

• v: select only from vertices and avoid connection to faces or edges.
• e: select only from vertices and/or edges and avoid connection to geometry faces.

Graph Select Tool

• Left-click and drag: zooms to the selected area.
• Right-click and drag: pans through the graph.
• Scroll middle mouse wheel: zooms all bounds in or out.

Graph Font Sizes

Constraint Enhancements

Option for Increasing Accuracy of Steady-State Results

The option to use frequency-dependent material properties on nondispersive materials has been added to the frequencies of interest tab when creating a new simulation. Also for a simulation, nondispersive materials are evaluated at a single frequency for time stepping, even if they are entered as a loss tangent or complex permittivity. When processing results for multiple steady-state frequencies, this option adjusts each material's permittivity, permeability, and conductivity to match the appropriate value at each requested frequency. This affects results including dissipated power, SAR, and magnetic flux.

In the image, the blue dots were generated from multiple simulations that used a sinusoid and associated conductivity at each frequency. The green and red plots represent two simulations that each had the material evaluation frequency set to 14 GHz. The red plot had the new option enabled and shows a higher level of accuracy. Using this option in conjunction with the near-field method of the dissipated power algorithm improves dissipated power and efficiency results over a range of steady-state frequencies.

By default, this option is disabled due to cases in which increased dissipated power can lead to a negative radiated power result. For example, Pradiated = Pinput−Pdissipated.

Increased FFT Resolution

The fast-fourier transform (FFT) algorithm generates more data points in the project's frequency range of interest with increased efficiency. This update increases the resolution, or smoothness, of frequency domain plots, such as S-parameters and impedance.

Users who increased the minimum plot FFT size in the application preferences for smoother frequency domain graphs should reduce this value; an FFT size of 21 is no longer necessary.

Failure Detection Script for GPU Memory

NVIDIA graphics cards have a nonzero failure rate, and those failures are not always catastrophic. Soft errors—such as a corrupted data bit stored in memory—can cause a simulation to compute odd results but are otherwise hard to detect. Remcom provides cuda_memtest, a Linux-based diagnostics script that detects failures on boards. This script can be set up on clusters and individual machines in order to test the cards on a nightly basis and notify system administrators of errors.

System administrators can either run the script manually or in a scheduling environment through XF's Linux installation directory: {install_dir}/remcom/bin/cuda_memtest. Additionally, cuda_tester.sh is provided as a starting point for administrators when implementing this capability on their clusters and remove a node if a failure is detected.