# Why is it divided into horizontal polarization and vertical polarization?

Of course, now that the electromagnetic simulation software is so developed, it is not relevant to the R&D personnel at the operational level if they don’t know. However, if we can understand the underlying knowledge, it will be more helpful for us to understand the nature of things.

(1) Where are the concepts of horizontal polarization and vertical polarization used?

In most cases, the actual antennas are inseparable from the radome. When analyzing the performance of the radome, the following concepts of horizontal polarization and vertical polarization are needed.

I remember that the undergraduate program I did at that time was to simulate the performance of a radome with physical optics under the guidance of the senior sister in the laboratory. The important step in the middle is to decompose the field radiated to the inner surface of the radome into horizontal polarization and vertical polarization, then calculate them separately, and finally add linearly.

Of course, now that the electromagnetic simulation software is so developed, it is not relevant to the R&D personnel at the operational level if they don’t know. However, if we can understand the underlying knowledge, it will be more helpful for us to understand the nature of things.

So why is it divided into horizontal polarization and vertical polarization?

(2) Definition of horizontal polarization and vertical polarization

When considering the oblique incidence of a plane wave from one medium to another, the horizontal polarization and vertical polarization are defined as follows. That is: when the electric field direction is ON the xz plane, it is horizontal polarization; when the electric field direction is perpendicular to the xz plane, it is vertical polarization.

The two media are distinguished by the positive and negative semi-axes of the z-axis, and they are extended on the y-axis, so the xy plane is the interface of the medium. The plane formed by the z-axis and the electric field direction of the incident wave is the incident surface. When the electric field direction is parallel to the incident surface, it is called horizontal polarization; when the electric field direction is perpendicular to the incident surface, it is called vertical polarization. The above is the definition when considering the propagation of electromagnetic waves between different media.

But in the field of radio wave propagation (such as in communications), the definition will be different. The linearly polarized wave when the electric field direction is parallel to the ground is called horizontal polarization; the linearly polarized wave when the electric field direction is perpendicular to the ground is called vertical polarization.

Sometimes, a linearly polarized wave is neither horizontally polarized nor vertically polarized; but it can be decomposed into a Linear superposition of horizontal polarization and vertical polarization.

(3) Transmission coefficient and reflection coefficient during horizontal polarization

It can be seen from Literature 2 that in horizontal polarization, its reflection coefficient and transmission coefficient are shown in the following figure: When θi = 0, that is, when the incident wave is incident perpendicular to the surface of the medium, θr = θt = 0. at this time, At this time, there is a special angle of incidence, called the Brewster angle, which makes Γ=0.

(4) Transmission coefficient and reflection coefficient during vertical polarization

It can be seen from Literature 2 that the reflection coefficient and transmission coefficient of the vertical polarization are shown in the following figure: When θi = 0, that is, when the incident wave is incident perpendicular to the surface of the medium, θr = θt = 0. at this time, When the vertically polarized wave propagates on the surface of the medium, there is no Brewster angle (making Γ = 0).

From the above formula, it can be understood that when analyzing electromagnetic waves propagating on different media surfaces, the reason for distinguishing between horizontal polarization and vertical polarization is that the transmission coefficient and reflection coefficient of the wave are different.

(1) Where are the concepts of horizontal polarization and vertical polarization used?

In most cases, the actual antennas are inseparable from the radome. When analyzing the performance of the radome, the following concepts of horizontal polarization and vertical polarization are needed.

I remember that the undergraduate program I did at that time was to simulate the performance of a radome with physical optics under the guidance of the senior sister in the laboratory. The important step in the middle is to decompose the field radiated to the inner surface of the radome into horizontal polarization and vertical polarization, then calculate them separately, and finally add linearly.

Of course, now that the electromagnetic simulation software is so developed, it is not relevant to the R&D personnel at the operational level if they don’t know. However, if we can understand the underlying knowledge, it will be more helpful for us to understand the nature of things.

So why is it divided into horizontal polarization and vertical polarization?

(2) Definition of horizontal polarization and vertical polarization

When considering the oblique incidence of a plane wave from one medium to another, the horizontal polarization and vertical polarization are defined as follows. That is: when the electric field direction is on the xz plane, it is horizontal polarization; when the electric field direction is perpendicular to the xz plane, it is vertical polarization.

The two media are distinguished by the positive and negative semi-axes of the z-axis, and they are extended on the y-axis, so the xy plane is the interface of the medium. The plane formed by the z-axis and the electric field direction of the incident wave is the incident surface. When the electric field direction is parallel to the incident surface, it is called horizontal polarization; when the electric field direction is perpendicular to the incident surface, it is called vertical polarization. The above is the definition when considering the propagation of electromagnetic waves between different media.

But in the field of radio wave propagation (such as in communications), the definition will be different. The linearly polarized wave when the electric field direction is parallel to the ground is called horizontal polarization; the linearly polarized wave when the electric field direction is perpendicular to the ground is called vertical polarization.

Sometimes, a linearly polarized wave is neither horizontally polarized nor vertically polarized; but it can be decomposed into a linear superposition of horizontal polarization and vertical polarization.

(3) Transmission coefficient and reflection coefficient during horizontal polarization

It can be seen from Literature 2 that in horizontal polarization, its reflection coefficient and transmission coefficient are shown in the following figure: When θi = 0, that is, when the incident wave is incident perpendicular to the surface of the medium, θr = θt = 0. at this time, At this time, there is a special angle of incidence, called the Brewster angle, which makes Γ=0.

(4) Transmission coefficient and reflection coefficient during vertical polarization

It can be seen from Literature 2 that the reflection coefficient and transmission coefficient of the vertical polarization are shown in the following figure: When θi = 0, that is, when the incident wave is incident perpendicular to the surface of the medium, θr = θt = 0. at this time, When the vertically polarized wave propagates on the surface of the medium, there is no Brewster angle (making Γ = 0).

From the above formula, it can be understood that when analyzing electromagnetic waves propagating on different media surfaces, the reason for distinguishing between horizontal polarization and vertical polarization is that the transmission coefficient and reflection coefficient of the wave are different.

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