Home / Technical Notes / Electromagnetic analysis / Analysis Condition / Error Correction of the Electromagnetic Field Originated in the Open Boundary

Error Correction of the Electromagnetic Field Originated in the Open Boundary

In order to calculate the open space accurately in the electromagnetic analysis, the air domain of, at least a quarter of wavelength, is needed around the antenna.

However, in the low frequencies, the needed analysis space becomes wider, which makes it difficult to analyze by Femtet. In such a case, error correction of the electromagnetic field originated in the open boundary

can improve the analysis accuracy even if the space around the antenna is narrow.

 

The calculations of directivity and surrounding electromagnetic field in the electromagnetic analysis solve the electromagnetic field outside the analysis domain based on the analysis results.

On the other hand, this corrective function corrects the electromagnetic field in the analysis domain and obtains more accurate filed results based on the analysis results. Its effect is shown in a monopole antenna model below.

 

 

Fig.1 Monopole antenna Fig.2 Electromagnetic fields generated by a monopole antenna in the wide space

 

 

 

The analysis model is shown in Figure 1. A linear antenna is placed on a plate-shaped electric wall (GND). A feeding point (port) is between the antenna and GND.

Fig.2 shows an isosurface contour diagram of the electric field, an analysis result by placing the monopole antenna in the wide space.

 

 

Fig.3 Electromagnetic field generated by a monopole antenna with open boundary condition placed nearby (Blue lines at the right side and above the antenna represent an open boundary).

Fig.4 Electromagnetic fields sown in Fig.3 are corrected.

 

 

Figure 3 shows the results of analysis where the antenna is close to the area set with the open boundary condition, and the air domain around the antenna is narrow.

The contour lines above the antenna are closed in Figure 2. But they are open in Figure 3 indicating that the electromagnetic field is not solved correctly. In Femtet, the open boundary is realized by setting the impedance of the plane waves.

With his method, however, if the open boundary and antenna are close to each other, the open boundary cannot be set properly, resulting in the results shown in Figure 3.

Figure 4 is the contour diagram after correcting the results of Figure 3. Its electromagnetic field is close to Figure 2. It can be said that this corrective function works well.

                

 

• See "Example 37: Electromagnetic Field Correction" for more details.
• Caution: The inside of dielectric and magnetic bodies cannot be corrected.

• Caution: The S-parameters and input impedance cannot be corrected.

• The number of bodies for correction must be minimized as the calculation takes time.

• Accuracy of correction near the open boundary is low.