A brief analysis of the design of a folding double-sided anti-metal RFID tag antenna

Folding patch tag antenna is a common form of RFID tag antenna, which consists of two layers of aluminum foil patches and one layer of PVC patch. This patch antenna is one of the most widely used antenna forms, but in practical applications, it is greatly affected by the metal surface, so certain measures need to be taken.

The antenna structure of the folding patch tag is composed of multiple folded and staggered wire layers. When the RFID signal enters from the top of the antenna structure, the signal will bounce layer by layer until it reaches the bottom and passes through the sensor; during this process, the signal will be constantly reflected and attenuated.

When the folding patch tag contacts the metal surface, the metal surface will reflect the signal, further interfering with the transmission of the signal. This interference affects the recognition rate and reading distance of the RFID Reader for the RFID electronic tag.

To solve this problem, the folding patch tag antenna adopts anti-metal technology. This technology reduces or eliminates the reflection interference of the metal surface on the RFID signal by limiting the propagation direction of the RFID signal and establishing a small gap between the tag and the metal surface.

The response of the folding patch tag antenna to the reflection of the metal surface is an important factor in its design and manufacture. Since RFID technology is different from other communication technologies, the design of RFID tag antennas requires special attention. When designing anti-metal tags, the interaction between the metal surface and the antenna reflection needs to be considered.

The folded UHF RFID double-sided anti-metal tag antenna is composed of a three-layer structure consisting of a top conductor layer, a bottom conductor layer and an intermediate layer; the intermediate layer is provided with a first deformable ring, a second deformable ring, a third deformable ring and a chip in a nested arrangement; the first deformable ring is U-shaped and is located at the outermost side of the intermediate layer; the second deformable ring is U-shaped and is located on the inner side of the first deformable ring; the third deformable ring is a square ring structure and is located on the inner side of the second deformable ring; the chip is arranged in the narrow gap between the two bent arms of the third deformable ring; the top conductor layer, the bottom conductor layer and the intermediate layer are filled with insulating materials, and one side of the three-layer structure is connected to the top conductor layer and the bottom conductor layer by a short-circuit wire on the left side, and the other side is connected to the three deformable rings and the bottom conductor layer by five short-circuit wires on the right side. The tag antenna has a simple structure and compact size, and does not require metal vias or short-circuit posts.

A typical folded structure patch antenna consists of a ground plane, a dielectric substrate and a conductive patch. Through time-varying signal excitation, there are conductive patches and metal ground planes on both sides of the dielectric substrate, and the thickness of the dielectric substrate is usually between 0.01λ and 0.05λ. When the patch antenna is working, a time-varying electric field is generated between the conductive patch and the ground plane, accompanied by surface currents on the surface of the conductive patch and the surface of the ground plane. The conductive patch antenna generates radiation at both ends of the patch perpendicular to the surface current.

After actual measurement and analysis, the electronic tag can effectively work in the ultra-high frequency RFID band required by my country on both sides in metal and non-metal environments, and has a compact size and can be widely used in specific IoT identification scenarios.