New App: Transmission Line Calculator
The transmission line parameters R, L, G, and C can be used to characterize any TEM and quasi-TEM waveguide structure. This app computes R, L, G, and C as well as the characteristic impedance and propagation constant for coaxial, twin lead, microstrip, and coplanar waveguide transmission lines.
A transmission line app that calculates R, L, G, and C as well as the characteristic impedance and propagation constant for coaxial, twin lead, microstrip, and coplanar waveguide transmission lines.
Multi-Turn Coil Improvements
New Coil Geometry Analysis
The Coil Current Calculation functionality available in previous versions of COMSOL Multiphysics has been replaced with a new Coil Geometry Analysis functionality. The user interface for this new functionality is almost identical to the old one, so users familiar with the previous Coil Current Calculation functionality will already be familiar with the usage of the new version. The new functionality has a number of significant advantages:
- Ability to handle coils with non-constant cross section and complex shapes.
- All coils can be solved for in a single study step.
- The solution method is robust: A converged solution indicates that the appropriate winding direction has been computed.
- The boundary conditions are simplified and require less user input.
Accurate Voltage Calculation
3D Multi-Turn Coils in frequency-domain studies are now more accurate. There is an automatic "filtering stage" to the coil current density calculation that significantly improves the accuracy of the computed electric field. Consequently, it also improves the accuracy of the computed coil voltage and other derived variables, such as power, inductance, etc. The current filtering stage is solved together with the main magnetic problem in the same study step; it does not require any interaction from the user. The functionality eliminates the need of tuning the coil domain conductivity in frequency-domain studies to obtain accurate solutions. It is active by default.
Coil Usability Improvements
Several minor improvements have been made to coil usability:
- Reorganization of the user interface to speed up workflow and model set-up.
- Easy set-up of coils in models with symmetry cuts.
- Circular coils can be used as part of sector-symmetric models.
Gauge Fixing Improvements
The Gauge Fixing feature has been improved. It requires less user input and has improved performance for complex models. Gauge Fixing is a technique used to determine the unique solution for magnetic fields problems. The feature will automatically work with anti-periodic models, models with multiple non-connected vector potential regions (Rotating Machinery problems) and models with a Mixed A-V and A formulation.
SPICE Export and New features for Electrical Circuit
The SPICE Export functionality is now available for the Electrical Circuit physics interface. Right-click on an Electrical Circuit physics and select "SPICE Export...". The COMSOL software will save a text file in the SPICE format representing the circuit currently modeled by the physics.
New devices and models have been added to the Electrical Circuits physics interface:
- PNP Bipolar Junction Transistor
- p-channel MOSFET
- Mutual Inductance (couples two inductors)
New Tutorial: Modeling a Spiral Inductor Coil
Spiral inductor coils are useful because they can be integrated easily while electroplating other printed circuits and they provide robust inductance values. The required computational resources for simulating such spiral inductors can become quite large as the number of turns increases. This example demonstrates how to exploit the near-symmetry of the structure to greatly reduce the model size. An eight-turn octagonal spiral coil is modeled using the Single Turn Coil boundary condition, with Floating Potential boundary conditions to enforce continuity of the current between the disjoint turns of the coil. The approach used in this example is valid when the operating frequency is sufficiently below the resonance of the inductor such that the capacitive coupling between the turns is negligible.