In the teaching of electromagnetic field and electromagnetic wave, Matlab programming is used to simulate the distribution of electromagnetic field and the transmission of electromagnetic wave, which makes the abstract concept intuitive and helps students to learn electromagnetic field and electromagnetic wave teaching content. The dynamic process of propagation, polarization, reflection and refraction of uniform plane electromagnetic waves is emphasized.
0 Preface
"Electromagnetic field and electromagnetic wave" is a compulsory basic course for undergraduates majoring in electronics and communication. The content covered by the course is an important part of the knowledge structure that should be possessed in the undergraduate stage of electronics and communication.
In the teaching process, students generally reflect that the course is relatively abstract, including a large number of mathematical formula derivation, many concepts are difficult to understand. No matter whether it is electromagnetic field or electromagnetic wave, it can't be seen or touched. Teachers are difficult to talk and students are difficult to understand. It is a common phenomenon in the current teaching of this course.
Matlab provides simulation conditions for the teaching of electromagnetic fields and electromagnetic waves due to its powerful functions, easy-to-learn programming language and visual simulation environment. Using Matlab to simulate and realize the visualization of the structure, the abstract concept is changed into clear, the complex formula is calculated and plotted, the electromagnetic field distribution and the electromagnetic wave propagation state are dynamically and intuitively described, and the students are understood and mastered the laws of electromagnetic field and electromagnetic wave propagation. Help students learn about this course. In this paper, Matlab is used to simulate the propagation, polarization, reflection and refraction of plane electromagnetic waves, and the abstract electromagnetic waveforms are imaged, which has achieved good teaching results.
1 Simulation of uniform plane electromagnetic wave propagation
Let the electromagnetic wave propagate along the z-axis. In the plane perpendicular to the z-axis, the points of the electromagnetic field have the same amplitude and vibration direction, that is, E and H are only related to z, and the electromagnetic waves are independent of x and y. Uniform planar electromagnetic waves.
1.1 The case where the electric field and the magnetic field have only one component
The instantaneous value of a uniform planar electromagnetic wave propagating along the z-axis can be expressed as follows:
Taking a uniform plane wave with a frequency of 100 MHz as an example in a linear, uniform, isotropic ideal medium, the process of electromagnetic wave propagation is dynamically simulated. Matlab's meshgrid, plot3, pause and other functions are used here. The color is the electric field strength and the red is the magnetic field strength. Through the graph, students can visually see that the electric and magnetic fields are perpendicular to each other, have the same phase, and change sinusoidally along the z-axis.
1.2 When the electric and magnetic fields have two components
Let the electromagnetic wave propagate along the z-axis direction, and select the two orthogonal directions ex and ey to describe the electric and magnetic fields. Then:
The propagation process of electromagnetic waves is shown in Figure 2.
2 Polarization of electromagnetic waves
Observed at a fixed point in space, the trajectory drawn by the vector endpoint of E in a time period represents the polarization of the electromagnetic wave. Understanding the polarization of electromagnetic waves is very useful in practical engineering. The simulation of the electric and magnetic fields in 1.2 is shown in Figure 3. Here, the view function is used to adjust the graphical viewpoint and observe the trajectory of the vector end. During the dynamic display, the polarization direction of the electromagnetic wave can be seen.
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