RFID antennas can be mainly divided into the following types

Dipole antenna: Also called a symmetrical dipole antenna, it consists of two straight wires of the same thickness and length arranged in a straight line. The signal is fed in from the two endpoints in the middle, and a certain current distribution will be generated on the two arms of the dipole. This current distribution will excite an electromagnetic field in the space around the antenna.

Microstrip patch antenna: It is usually a thin layer of metal patch attached to the ground plane. Microstrip patch antenna is light in weight, small in size, and thin in section. The feeder and matching network can be produced at the same time as the antenna, and is closely related to the communication system. Printed circuits are integrated together, and the patches can be manufactured using photolithography processes, which are low-cost and easy to mass-produce.

Inductively Coupled Antennas: Inductively coupled  antennas are commonly used for communication between readers and tags, where they couple through a shared magnetic field. These antennas are usually in a spiral shape to create a shared magnetic field between the reader and tag.

Coil Antenna: Coil antenna is one of the most widely used antennas in RFID systems. They are usually made of wires wound into circular or rectangular structures to enable them to receive and transmit electromagnetic signals.

Yagi Antenna: A Yagi antenna is a directional antenna consisting of two or more half-wave dipoles. They are often used to enhance signal strength or conduct directional wireless communications.

Helical Antenna: A helical antenna is an antenna capable of receiving and transmitting circularly polarized electromagnetic waves. They are usually made of metal wire or sheet metal and have one or more spiral-shaped structures.

Microstrip line antenna: A microstrip line antenna is a miniaturized and thin antenna that is usually used in small devices such as mobile devices and RFID tags. They are constructed from microstrip lines that provide good performance in a smaller size.

Cavity-backed antenna: A cavity-backed antenna is an antenna in which the antenna and feeder are placed in the same back cavity. They are commonly used in high-frequency RFID systems and can provide good signal quality and stability.

The above are the main classifications of RFID antennas. Each type of antenna has its unique characteristics and applicable scenarios. When choosing a suitable RFID antenna, you need to make a selection based on actual application requirements and environmental conditions.