Performance difference between circular and linear polarization of antennas!

The polarization of an antenna is determined in terms of the polarization of an electromagnetic wave. The direction of polarization of an electromagnetic wave is usually described in terms of the spatial pointing of its electric field vector, i.e., the trajectory depicted by the change in the orientation of its electric field vector in space over time when viewed along the direction of propagation of the electromagnetic wave at a certain location in space. If this trajectory is a straight line, it is called a line polarization, and if it is a circle, it is called a circular polarization. Generally speaking the direction of antenna polarization is the direction of the electric field. The following is a brief discussion of the performance difference between circular polarization and line polarization of RFID reader antenna. Circular polarized antenna electromagnetic field emission for the spiral beam, has the following characteristics: 1) antenna RF energy to circular spiral antenna emission; 2) circular spiral beam with multi-directional electromagnetic field, electromagnetic field range is broader, but relative to the line polarized antenna for the intensity of the smaller; 3) read the space is wide, but relative to the line polarized antenna for the unidirectional tags sensitivity is small and read the distance is shorter; 4) suitable for The direction of travel is not sure of the label (marking objects). Circular polarized antenna circular electromagnetic beam can be sent in all directions at the same time. When encountering obstacles, circular polarized antenna electromagnetic beam has strong elasticity and bypassing ability, increasing the label from all directions into the antenna reading probability, so the label of the paste and the direction of travel is relatively tolerant; but the broadness of the circular beam also brings the relative reduction of electromagnetic wave intensity, so that the label can only enjoy a part of a certain direction of the electromagnetic wave energy, and make the reading distance relatively shorter. It can be said that circularly polarized antenna is at the expense of reading distance, in exchange for reading the wide range. Circular polarization antenna is adapted to the label (identification object) travel direction unknown occasions, such as distribution center of goods cache area and so on. Line polarization antenna reader antenna sends out electromagnetic wave is linear, its electromagnetic field has strong directionality, has the following characteristics: 1) wireless radio frequency energy in a linear way from the antenna emission; 2) linear beam has unidirectional electromagnetic field, relative to circular polarization antenna in terms of the electromagnetic field is strong, but the range is narrower and longer; 3) relative to the circular antenna unidirectional reading distance is longer, but due to the direction of the strong, and thus the reading width is narrower; reading width; 3) relative to circular antenna single direction reading distance is longer, but because of strong direction, and thus the reading width is narrower. Read width is narrower; 4) adapted to the direction of travel to determine the label (identification object). When the RFID tag and reader antenna parallel, line polarization antenna has a better reading rate, therefore, line polarization antenna is generally used to identify the direction of travel of the object known tag reading, such as pallets. As the antenna electromagnetic wave beam is limited to the read-write antenna plane size within a narrow range, the energy is relatively concentrated, can penetrate the density of the material, so, the density of the material has a better penetration, suitable for higher density of the marking object, such as flour, printing paper and so on. Line polarization antenna is actually sacrificed to read the range of breadth, in exchange for the label sensitivity strength and unidirectional reading distance length, therefore, the use of tags and reader antenna must be parallel to the plane of the entity, in order to have a good reading effect, if the label plane perpendicular to the plane of the entity of the reader antenna, will not be able to read the label data.

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