Antenna Design

An antenna is a device that uses resonance technology in conjunction with electromagnetic waves to radiate or receive radio frequency signals. Antennas can be divided into long wave, short wave, ultra short wave, and microwave antennas according to their operating frequency bands; According to directionality, it can be divided into omnidirectional antennas, directional antennas, etc; According to their appearance, they can be divided into linear antennas, planar antennas, etc. In RFID systems, antennas are divided into two types: tags and readers. Currently, RFID systems mainly focus on the LF, HF, UHF, and SHF frequency bands. The principle and design of antennas are fundamentally different in the LF, HF, and UHF frequency bands, and the structure of antennas also undergoes significant changes. In essence, due to the wavelength range of several hundred meters in the LF and HF frequency bands, it is very difficult to transmit electromagnetic waves. The near-field region is mainly dominated by the magnetic field characteristics of the energized solenoid antenna, with little or no propagation of electromagnetic waves. The electromagnetic wave characteristics of the antenna are mainly concentrated in the UHF and microwave frequency bands. The main characteristics and usage of electronic tags distinguished by working frequency bands are shown in the parameter table,

Frequency band division: Low frequency long band (LF) KHz High frequency short wave (HF) MHz Ultra high frequency decimeter wave (UHF) MHz Ultra high frequency microwave (SHF) GHz

Typical frequency 125 13.56 430/900 2.45 or above

Antenna principle: Magnetic field coupling, electromagnetic field coupling, electromagnetic wave emission

Directional characteristics close to omnidirectional orientation<=50 degrees orientation<=30 degrees antenna production winding antenna winding/etching/stamping etching/printing antenna material self-adhesive enameled wire self-adhesive wire/aluminum/copper aluminum/conductive ink packaging method cob module cob/direct welding/inverted flip key bonding packaging material paper/PVC paper/film film film usage distance 0.1-1.0M 0.1-1.0M 1-10M>=3.0M or more

Label antenna design: The purpose of using an antenna is to transmit the maximum energy into and out of the label chip through the antenna. This will require a finely designed antenna to improve performance, while also taking into account the matching of connected label impedance. Typically, the input impedance is 50 ohms. In order to increase transmission distance and reduce antenna size, research on UHF antennas is a key focus. The characteristics of tag antennas are influenced by the shape, material, and physical properties of the identified object, which will directly affect the performance of the antenna. In the process of designing tag antennas, the above factors must be fully considered. At the same time, to improve the sensitivity of the tag, it is necessary to try to increase the gain of the tag, and antennas with high gain are manifested in larger sizes. Therefore, in order to meet the requirements of small size and low cost, it is very necessary to develop various enhanced UHF antennas.

Reader antenna design: For applications in close range (=10cm) systems, such as access control systems, the antenna is generally integrated with the reader; For electronic tag systems with long-distance HF (10cm-1m) or UHF frequency band (=3cm), the antenna and reader must adopt a split structure and be connected together through a 50 ohm impedance matched coaxial cable. As shown in Figure 4, the split UHF tag reader and writer produced by Shanghai Zhelin's agent, Yitengmai. In practical use, due to the diverse installation and usage environments of the equipment, it is required that the reader antenna design adopt low profile, small size, and broadband coverage. At the same time, it also involves the low efficiency and low gain brought about by antenna miniaturization (antenna array combinations can be used to improve gain), which is also a research topic at home and abroad.