What Is an Antenna Map?

Also called radiation pattern, far-field pattern.

The so-called antenna pattern refers to the graph of the relative field strength (normalized mode value) of the radiation field as a function of direction at a certain distance from the antenna. Usually, two mutually perpendicular plane patterns in the direction of the maximum radiation of the antenna To represent.

1. A line antenna installed on the ground generally uses two mutually perpendicular planes to indicate its pattern. That is, a horizontal plane pattern and a vertical plane pattern.

2. UHF antennas are usually represented by two planes parallel to the field vector, that is, the E-plane pattern and the H-plane pattern.

In order to facilitate the comparison of the pattern characteristics of various antennas, some characteristic parameters need to be specified. Mainly include: main lobe width, side lobe level, front-to-back ratio, direction coefficient, etc.

1. Main lobe width: It is a physical quantity that measures the sharpness of the antenna's maximum radiation area. The width between the two half power points of the main lobe of the antenna pattern is usually taken.

2. Sidelobe level: refers to the level of the first sidelobe closest to the main lobe and the highest level, usually expressed in decibels.

3. Front-to-back ratio: The ratio of the maximum radiation direction (forward) level to the opposite direction (backward) level, usually in decibels.

4. Direction coefficient: The ratio of the radiated power flow density of the antenna in the maximum radiation direction to the ideal non-directional antenna of the same radiated power at the same distance at a certain distance from the antenna.

The pattern of the electromagnetic field radiated by the antenna on a spherical surface centered on the antenna with a certain distance and radius as a function of space angle (including azimuth and elevation) is called a radiation pattern, which is referred to as a pattern. The radius of the sphere, that is, the distance from the field point to the antenna, must meet the far-field conditions.

Because the antenna pattern is generally petal-shaped, it is also called a lobe pattern. The beam within the first zero radiation direction line on both sides of the maximum radiation direction is called the main lobe, and the beam opposite to the main lobe direction is called the back lobe. Beams between zero radiation directions are called sidelobes or sidelobes. ^[1]