Bugs

Bug 1: Metal layers with thickness do not make contact with ports

• There will be no contact between a micro stripline port with a metal layer that has layers.thickness set to a non-zero value.
• Only way to guarantee contact is to use a 0 thickness metal layer.
• Symptoms include the S parameters and impedance showing an open circuit at low frequencies (< 1GHz).

Bug 2: openEMS produces corrupt data if the simulation timestep is too fast

• Symptoms include postprocessing of data failing due to corrupted port data.
• Can be visually seen by going to ems/simulation/{excited_port}/port_it_{port}.
• Numbers will be mangled and there will be missing rows and columns.
• To avoid this you have to make each timestep more expensive to run.
• Modify the PCB mesh properties to fix this
  • Decrease mesh.xy to increase the grid resolution along x and y axes.
  • Increase mesh.inter_layers to increase grid resolution along z axis.
  • Decrease mesh.smoothing_ratio to increase number of grid lines overall.
• Modify the simulation settings to fix this
  • Increase margin.xy and margin.z to increase size of the air gap to simulate around the PCB.

Bug 3: openEMS will randomly crash

• When running openEMS simulation through there is a small chance of crashing with a segmentation error.
• Rerunning until it stops crashing is the only know work around.
• Use the retry script at ./scripts/retry.sh to repeat a command until a successful pass is done.
• Break down simulation into multiple steps along with the retry script to automate around openEMS crashes.

# Create convenient alias in bash shell
alias retry=$(realpath ./scripts/retry.sh)

# Go to differential pair example
cd ./examples/differential

# Convert Gerber to image conversion step (does not crash)
gerber2ems --convert

# Create openEMS geometry files (does not crash)
gerber2ems --geometry

# Run openEMS simulation (this can crash)
retry gerber2ems --simulate

# Postprocess data (this can crash since we use openEMS api to parse simulation results)
retry gerber2ems --postprocess

# Render data (this can crash since we use openEMS api to parse simulation results)
retry gerber2ems --render