The antenna features are related to the shape, size and composition of the antenna. GPS Antenna The size of the antenna is generally measured by the wavelength of the antenna transmitting or receiving electromagnetic waves. The radiation characteristics of the dipole antenna, which works at a wavelength of L = 2m long 1m, are the same as the dipole antenna that works at wavelength L = 2cm. Parameters related to antenna directivity: directional function or directional map the mathematical expression describing the relative distribution of the electromagnetic field strength of the antenna radiation in space is at a certain distance from the antenna, GPS Antenna called the directional function of the antenna, and the directional function is represented by a graph. The maximum radiant beam is usually referred to as the main lobe of the directional map. A few small beams next to the main lobe are called Sidelobe.
Antenna gain is a measure of the radiation intensity of an antenna in a given direction in a wave-array plane. It is the ratio of the radiation intensity of the antenna in the maximum radiation direction to the maximum radiation intensity produced by an isotropic antenna with the same input power in the antenna at the same point.
Antenna radiation resistance rσ used to measure the power of the antenna radiation, GPS Antenna it is a virtual volume, defined as follows: There is a resistor rσ, when the current through the antenna is equal to the maximum current, the loss of power is equal to the radiation power. Obviously, GPS Antenna the greater the radiation resistance, the stronger the radiation capability of the antenna.
The polarization characteristic is the law that the direction of the electric field vector changes with time in the maximum radiation direction of the antenna. According to the polarization form of the electric field radiated by the antenna, the antenna can be divided into linear polarization antenna, GPS Antenna circularly polarized antenna and elliptical polarization antenna. The linear polarization can be divided into horizontal and vertical polarization, and both circular and elliptical polarization can be divided into left and right.
Input impedance and voltage standing wave ratio: the input impedance of the antenna is equal to the characteristic impedance of the transmission line in order to get the maximum power of the antenna. GPS Antenna When the frequency of the line work deviates from the design frequency, the matching between the antenna and the transmission line becomes worse, which causes the voltage standing wave ratio of the transmission line to increase and the antenna efficiency is reduced. Therefore, in practical application, the voltage standing wave ratio parameter is also introduced, GPS Antenna and the standing wave ratio cannot be greater than a specified value.
The electrical parameters of the antenna are related to the frequency, when the operating frequency deviates from the design frequency, it often causes the change of the antenna parameters. GPS Antenna When the operating frequency changes, the antenna’s relevant electrical parameters should not exceed the specified range, this frequency range is called band width, short for the antenna bandwidth.
Most antennas have reciprocity, that is, GPS Antenna the antenna has the same directionality in transmitting mode and receiving mode. If a given antenna works in the firing mode, a direction of radiation electromagnetic capacity than the B-direction strong 100 times times, GPS Antenna then the end of the antenna work in the receiving mode, receiving a direction radiation from the electromagnetic sensitivity is 100 times times stronger than B direction.
Post time: Sep-25-2018