Hello,

In Characteristic Mode Analysis (CMA) within CST Studio Suite, mode selection involves identifying and choosing the most relevant modes for a specific frequency or design objective. This process helps engineers understand the behavior of a conducting surface and optimize antenna designs or other high-frequency components.

Here's a more detailed breakdown:

1. Understanding Characteristic Modes:

• CMA calculates a set of orthogonal current modes that can exist on a conducting surface, like the modes on a metal plate.
• These modes represent different ways a current can flow on the surface at specific frequencies.
• Each mode has a characteristic frequency and a corresponding field pattern.

2. Mode Significance:

• CMA calculates a "modal significance" value for each mode, indicating its relative dominance at a given frequency.
• Higher significance values suggest that a mode is more likely to be excited and contribute to the overall electromagnetic behavior.
• This information helps engineers identify the most important modes for a particular application.

3. Selecting Relevant Modes:

• By Frequency:When working with specific frequencies, engineers can examine the mode significance plot to identify modes that are significant at those frequencies.
• By Design Goal:If the goal is to maximize gain or bandwidth, the most significant modes at the target frequencies are likely the most relevant.
• By Mode Type:Depending on the antenna type, engineers may prioritize certain mode types (e.g., TM01, TM10).
• By Radiation Pattern:CMA also calculates the far-field radiation pattern for each mode, which can be used to select modes with desired radiation characteristics.

4. CST Studio Suite CMA Tool:

• The CMA tool is built into CST Studio Suite's Integral Equation Solver and Multilayer Solver.
• It automatically calculates modes, their significance, radiation patterns, and surface current distributions.
• It also provides automatic mode tracking, which helps engineers follow modes as they change with design modifications.

5. Example Scenario:

• Consider designing a multi-band printed antenna.
• CMA can be used to identify the current modes on the antenna at the desired resonant frequencies.
• The designer can then optimize the antenna's geometry to increase coupling to the desired modes, improving performance at those frequencies.

In summary, mode selection in CMA involves identifying and prioritizing modes based on their significance and relevance to the design goals, allowing engineers to effectively tune antennas and other high-frequency devices.

Cma tool is a comprehensive feature of CST MWS similar to the Eigen mode solver, which gives the possible resonating modes and its oscillating field pattern in the patch antenna makes it easier to achieve the desired characteristics for radiation. As in trainset solver, only a specific mode comes to play which depends upon the excitation configuration, but CMA can be effectively utilized to oversee the characteristics of patches to maximize the gain performance, bandwidth and higher order mode rejection.

An example of a simple rectangular patch with 5 modes: TM01, TM10, TM11, TM21 simulated using integral equation solver to visualize the different modes, while the mode significance plot gives the information of occurrence frequencies very helpful in order to reject higher order mode.

Thanks,

CMA analysis in CST which solver we use either Multilayer solver or Integral equation solver. Which one provide better results.