In the field of vocal music, the frequency band refers to the sound frequency. The human ear feels the sound frequency from the lowest 20Hz to the highest 20KHz, while the human voice frequency range is concentrated between 80Hz~12kHz. People's feelings are different.
Antenna gain refers to the ratio of the power density of the signal generated by the actual antenna and the ideal radiating element at the same point in space under the condition of equal input power. It quantitatively describes the extent to which an antenna concentrates the input power. The gain is obviously closely related to the antenna pattern. The narrower the main lobe of the pattern, the smaller the side lobes and the higher the gain. Antenna gain is a measure of the ability of an antenna to transmit and receive signals in a particular direction. It is one of the most important parameters for selecting a base station antenna. In addition, the parameters characterizing the antenna gain are dBd and dBi. DBi is the gain relative to the point source antenna, and the radiation in all directions is uniform; dBd is dBi=dBd+2.15 with respect to the gain of the symmetric array antenna. Under the same conditions, the higher the gain, the farther the wave travels.
Standing wave ratio
The meaning of the standing wave ratio: The standing wave ratio is a numerical value used to indicate whether the antenna and the radio wave transmitting station match. If the value of SWR is equal to 1, it means that the radio wave transmitted to the antenna does not have any reflection, and all are emitted. This is the most Ideally. If the SWR value is greater than 1, it means that some of the electric wave is reflected back and eventually becomes heat, which makes the feeder warm. The reflected electric wave can also generate a relatively high voltage at the output of the launching station, which may damage the launching platform.
The antenna polarization mode is mainly divided into linear polarization, circular polarization and elliptical polarization. When the electric field vector orientation of the antenna changes with time, the vector endpoint is a circle in the plane perpendicular to the propagation direction, called a circle. A polarized antenna, when the electric field vector orientation of the antenna changes with time, its vector endpoint is an ellipse in a plane perpendicular to the direction of propagation, called an elliptical polarized antenna, and the antenna electric field vector is fixed in space. Polarized for the line. The linear polarization is divided into horizontal polarization and vertical polarization. When the electric field strength direction is perpendicular to the ground, the electric wave is called vertical polarized wave; when the electric field strength direction is parallel to the ground, the electric wave is called horizontal polarization wave.
Applied to RFID antennas in complex media environments, as long as the appropriate design method is mastered, it is not only easy to achieve the expected design goals, but also simplifies the original complicated work, and the design goals, design cycles, and design costs are transparent. Don't choose a suitable antenna by making a large number of antennas of various shapes to pass the performance test or test, because we already know what kind of antenna is suitable.