Antenna basic knowledge
The total input power ratio of the antenna, said the maximum gain factor of the antenna. It is a more complete reflection of the antenna's effective use of the total RF power than the antenna directivity factor. And expressed in decibels. It can be mathematically deduced that the maximum antenna gain factor is equal to the product of the antenna directivity factor and the antenna efficiency.
It refers to the antenna radiation out of the power (that is, the effective conversion of electromagnetic wave power) and the input to the antenna active power ratio. Is constant less than 1 value.
Antenna polarized wave
When the electromagnetic wave is propagating in space, if the direction of the electric field vector remains fixed or rotates according to a certain law, this electromagnetic wave is called a polarized wave, which is also called an antenna polarized wave or a polarized wave. Generally can be divided into plane polarization (including horizontal and vertical polarization), circular polarization and elliptical polarization.
Polarization direction
The direction of the electric field of a polarized electromagnetic wave is called the direction of polarization.
Polarization surface
Polarized electromagnetic wave polarization direction and propagation direction of the plane formed by the plane called the polarization.
Vertical polarization
The polarization of radio waves, often with the earth as a standard surface. Any polarization plane and the earth normal surface (vertical) parallel to the polarization is called the vertical polarization. Its electric field direction and the earth vertical.
Horizontal polarization
Polarized surface and normal earth surface perpendicular to the polarized wave is called the horizontal polarization. Its electric field direction and the earth parallel.
Plane polarization
If the direction of polarization of electromagnetic waves to maintain a fixed direction, called plane polarization, also known as linear polarization. In the electric field parallel to the Earth's component (horizontal component) and perpendicular to the Earth's surface components, the spatial amplitude of any relative size, can be planar polarization. Vertical polarization and horizontal polarization are all special cases of plane polarization.
Circular polarization
When the angle between the plane of the radio wave and the earth's normal plane changes from 0 to 360 °, that is, the size of the electric field does not change and the direction changes with time. The end of the electric field vector locates in a plane perpendicular to the propagation direction When the projection is a circle, it is called circular polarization. Circular polarization can be obtained when the amplitude of the horizontal component and the vertical component of the electric field are equal and the phases are different by 90 ° or 270 °. Circular polarization, if the polarization plane rotates with time and the direction of the electromagnetic wave into the right spiral relationship, said the right circular polarization; the other hand, if the left spiral relationship, said the left circular polarization.
Elliptic polarization
If the angle between the radio wave polarization plane and the normal earth surface changes periodically from 0 to 2π and the trajectory of the end of the electric field vector is an ellipse projected on a plane perpendicular to the propagation direction, it is called elliptical polarization. When the amplitudes and phases of the vertical and horizontal components of an electric field have arbitrary values (with the exception of the two components being
