Yes, even if only the lower frequency is defined in the analysis setup, the axial ratio at the other operating band can still be evaluated, provided that a frequency sweep has been defined. However, if the simulation is performed at a single frequency without a sweep, the axial ratio at other bands cannot be obtained.

Hello,

To check the axial ratio (AR) for a multiband antenna in commercial simulation software like CST or HFSS, you'll generally follow these steps: define a far-field monitor, set the desired frequency range and angular resolution, select axial ratio calculation, and then analyze the results. The specific steps may vary slightly between different software packages.

Here's a more detailed breakdown:

1. Define a Far-Field Monitor:

• In your simulation software (e.g., CST or HFSS), you'll need to set up a far-field monitor. This monitor captures the antenna's radiation pattern at a distance, allowing you to analyze parameters like gain, polarization, and axial ratio.
• This monitor is typically associated with a specific frequency or frequency range. For a multiband antenna, you'll need to define the monitor to cover all the desired frequency bands.

2. Set Frequency Range and Angular Resolution:

• Specify the frequency range for your axial ratio calculation. For a multiband antenna, this will include all the frequency bands of interest.
• Define the angular resolution for the far-field calculation. A finer resolution (smaller angular steps) provides a more detailed axial ratio plot, but it also increases simulation time.

3. Select Axial Ratio Calculation:

• Within the far-field monitor settings, locate the polarization or axial ratio calculation options.
• Choose to calculate the axial ratio. This might involve selecting "Axial Ratio," "Polarization," or similar terminology, depending on the software.
• You may also need to specify whether you are interested in left-hand circular polarization (LHCP) or right-hand circular polarization (RHCP).

4. Analyze the Results:

• After running the simulation, the software will generate data for the axial ratio as a function of frequency and angle.
• For a multiband antenna, you'll see the axial ratio plotted for each frequency band.
• The axial ratio is typically expressed in dB. A value close to 0 dB indicates good circular polarization. Values above 3 dB are generally considered to have poor circular polarization.

5. Understanding the Results:

• The axial ratio indicates how well the antenna maintains circular polarization. A lower axial ratio (closer to 0 dB) is desirable.
• For each frequency band of the multiband antenna, you'll need to analyze the axial ratio to ensure it meets the desired performance criteria.
• You may also want to examine the axial ratio as a function of direction (azimuth and elevation angles). This will help you understand how well the antenna maintains circular polarization across its radiation pattern.

Example in CST:

Key Considerations:

• Circular Polarization:Axial ratio is primarily relevant for circularly polarized antennas. For linearly polarized antennas, other parameters like gain and radiation pattern are more important.
• Bandwidth:For a multiband antenna, you'll want to ensure good axial ratio performance across all operating frequency bands.
• Software Specifics:The exact steps and terminology may vary slightly between different software packages (e.g., CST, HFSS, ADS). Refer to the documentation for your specific software for detailed instructions.
• Thanks,

this link may help you

https://www.ainfoinc.com/blog/blog-how-to-measure-the-axial-ratio-of-the-circular-polarizer.html

Janipasha Shaik No, you cannot correctly check the axial ratio at another band operating frequency if your simulation was set up for only a single (lower) frequency. You must include the desired frequency in the simulation sweep or setup to obtain valid axial ratio data at that band.

To check the axial ratio at multiple band operating frequencies, you should: