Satellite Antenne Gain is the ratio of the total input power to the maximum gain of the antenna. It reflects the effective utilization of the antenna for the total RF power, more comprehensively than the directional coefficient. It is expressed in decibels. It can be mathematically proved that the maximum gain coefficient of a satellite antenna is equal to the product of the directional coefficient and the antenna efficiency.
It refers to the ratio of the radiation power (i.e., the power conversion part of the electromagnetic wave) radiated by the antenne to the active power input to the antenna. It is a constant value less than 1.
When an electromagnetic wave propagates in space, if the direction of the electric field vector remains fixed or rotates according to a certain rule, it is called a polarized wave, also known as an antenna polarized wave, or a polarized wave. It is usually divided into plane polarization (including horizontal polarization and vertical polarization), circular polarization, and elliptical polarization.
The polarization direction of polarized electromagnetic waves is called the polarization direction.
The plane composed of the polarization direction of the polarized electromagnetic wave and the propagation direction is called the polarization plane.
For radio waves, the polarization is often based on the ground. A polarized wave that is parallel to the polarization plane of the ground normal (vertical plane) is called a vertical polarized wave. Its electric field direction is perpendicular to the ground.
A polarized wave that is perpendicular to the polarization plane of the ground normal is called a horizontal polarized wave. Its electric field direction is parallel to the ground.
If the polarization direction of the electromagnetic wave remains fixed, it is called planar polarization or linear polarization. When the space amplitudes of the electric field parallel to the ground (horizontal component) and perpendicular to the ground surface have arbitrary relative magnitudes, planar polarization can be obtained. Both vertical polarization and horizontal polarization are special cases of planar polarization.
When the angle between the polarization plane of the radio wave and the ground normal plane changes in cycles from 0 to 360 degrees, i.e., the electric field size remains unchanged but the direction changes with time, the trajectory of the electric field vector endpoint projected on the plane perpendicular to the propagation direction is a circle, called circular polarization.
Circular polarization can be obtained when the amplitudes and phase differences of the horizontal and vertical components of the electric field are equal (except when the two components are equal). If the polarization plane rotates with time and forms a right-handed spiral relationship with the direction of the electromagnetic wave propagation, it is called right circular polarization; otherwise, it is called left circular polarization.
When the angle between the polarization plane of the radio wave and the ground normal plane changes periodically from 0 to 2π, and the trajectory of the electric field vector endpoint projected on the plane perpendicular to the propagation direction is an ellipse, it is called elliptical polarization.
Elliptical polarization can be obtained when the amplitudes and phases of the vertical and horizontal components of the electric field have arbitrary values (except when the two components are equal).