What indicators are mainly involved in the design of RFID antennas

Frequency band

In the field of vocal music, the frequency band refers to the sound frequency. The human ear's perception of the sound frequency is from the lowest 20Hz to the highest 20KHz, while the human voice frequency range is concentrated between 80Hz and 12kHz. People's feelings are different.

Gain

Antenna gain refers to the ratio of the power density of the signal generated by the actual antenna and the ideal radiating unit at the same point in space under the condition of equal input power. It quantitatively describes the degree to which an antenna concentrates the input power and radiates it. The gain is obviously closely related to the antenna pattern, the narrower the main lobe of the pattern, the smaller the side lobe, and the higher the gain. Antenna gain is used to measure the ability of an antenna to send and receive signals in a specific direction, and it is one of the most important parameters for selecting a base station antenna. In addition, the parameters that characterize the antenna gain include dBd and dBi. DBi is the gain relative to the point source antenna, and the radiation in all directions is uniform; dBd relative to the gain of the symmetrical array antenna dBi=dBd+2.15. Under the same conditions, the higher the gain, the farther the radio wave travels.

VSWR

The meaning of the standing wave ratio: the standing wave ratio is a value, which is used to indicate whether the antenna and the radio wave transmitter match. If the value of SWR is equal to 1, it means that the radio waves transmitted to the antenna are transmitted without any reflection, which is the most Ideal situation. If the SWR value is greater than 1, it means that a part of the electric wave is reflected back and eventually turns into heat, which makes the feeder heat up. The reflected electric wave can also generate a fairly high voltage at the output of the transmitter, which may damage the transmitter. .

  Polarization mode

Antenna polarization methods are mainly divided into linear polarization, circular polarization, and elliptical polarization. When the orientation of the electric field vector of the antenna changes with the time plane, its vector endpoints describe a circle in a plane perpendicular to the propagation direction, called a circle. For a polarized antenna, when the orientation of the electric field vector of the antenna changes with the time plane, its vector endpoints describe an ellipse in a plane perpendicular to the propagation direction, which is called an elliptical polarized antenna, and the orientation of the antenna's electric field vector in space is fixed. for linear polarization. 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 vertically polarized wave; when the electric field strength direction is parallel to the ground, the electric wave is called horizontal polarization. Wave.

Conclusion

Applied to RFID Antennas in complex media environments, as long as the appropriate design method is mastered, not only is it easy to achieve the expected design goals, but it will also simplify the original complicated work, and the design goals, design cycle, and design costs will be transparent. Don't choose a suitable antenna by making a lot of antennas of various shapes through performance tests or experiments, because we already know what kind of antenna is suitable.