What are the design steps for an RFID antenna

RFID antenna design requires not only considering the application scenario but also tailoring the design to specific application requirements, within a specified size range, to match the chip. Therefore, the design process focuses on achieving conjugate matching between the antenna's input impedance and the chip's operating frequency band within the specified size range and operating environment. Besides impedance matching, parameters such as antenna radiation efficiency, polarization direction, and radiation pattern also need attention.       

 What are the steps in RFID antenna design?        Based on the design requirements (tag size, operating frequency band, matching chip, application conditions, etc., specified in the requirements), determine the design scheme and target parameters, establish an antenna model, and perform simulation calculations on the antenna model. Then, adjust the design model based on the simulation results to achieve the expected target parameters. In antenna design, the parameters of various materials and structural distributions are usually determined, and the conditions are generally fixed. However, RFID tags have a wide range of applications. If the dielectric constant of materials is not known, the input impedance and other parameters of the antenna in this environment become unknown, requiring testing to determine these parameters.        1. Equivalent Measurement of Tag Antennas        As can be seen from the general design methods of tag antennas, the key to design is testing. RFID antennas are divided into high-frequency and ultra-high-frequency antennas. For high-frequency antennas, the dielectric effect can usually be ignored, and their inductance and distributed capacitance can be directly measured using a bridge or impedance analyzer. Precise measurement of ultra-high-frequency antennas is more difficult to achieve, and is usually achieved through equivalent measurement. The following introduces two measurement methods suitable for ultra-high-frequency RFID antenna design:        (1) Resonance Method for Measuring Equivalent Dielectric Constant        The input impedance of UHF tag antennas is quite sensitive to materials. When attached to different materials, the impedance change usually varies significantly. The equivalent dielectric constant refers to treating the composite material as a homogeneous material, and the overall effect of the composite material on the antenna as the effect of a homogeneous material.        The input impedance curve shows the frequency bands around which the real part of the antenna input impedance reaches its maximum and minimum values. The corresponding maximum and minimum values are the resonant frequency bands of the antenna. Then, simulation calculations are performed according to the dimensions of the composite board. When calculating the dielectric constant of the composite board, the maximum real part of the simulated input impedance of the antenna can also be obtained. Once the equivalent dielectric constant of the composite board is determined, the tag antenna can be designed using normal design methods.        (2) Application of Scaled Model Technology and Proportional Measurement Method        Scaled model technology refers to reducing (or enlarging) the antenna by a certain scale under certain conditions, and its characteristic parameters also change functionally according to this scale.        Scaled model technology is usually used to facilitate testing by creating a model suitable for testing and performing equivalent tests. The design and measurement of RFID tag antennas can also directly use scaled model technology for equivalent measurement. The proportional measurement method can directly determine the design target in complex environments, which is faster and reduces workload than the equivalent dielectric constant measurement method. This method is highly practical in actual engineering design.        2. Determination of the Design Frequency Band for Tag Antennas        Because the frequency band standards of each country are different for UHF RFID, the design frequency band must first be determined according to the requirements for tag antenna design. Antenna design using the equivalent antenna measurement algorithm requires multiplying the designed frequency band by a scaling factor K.        The formulas are as follows:        Fmin = Fminnominal × K = Minimum frequency band        Fmax = Fmaxnominal × K = Maximum frequency band        The goal is to achieve the target values for the antenna's characteristic parameters within this frequency band. Using the equivalent antenna measurement algorithm for antenna design can save considerable simulation calculations, especially when the frequency band is clearly defined under simple conditions (pure antenna), simplifying what would otherwise be complex calculations.        3. Dynamic Impedance Matching Design        The chip's input impedance changes with frequency. When the chip is bonded to the antenna, distributed capacitance is added, resulting in a difference between the chip's actual input impedance and its nominal value. To ensure stable tag operation and meet impedance matching requirements across a wide frequency band, dynamic impedance matching design is typically implemented during tag antenna design, considering the dynamic changes in the chip's input impedance.        The design steps for RFID antennas are basically fixed. Even for RFID antennas used in complex media environments, as long as you master the appropriate design scheme, you can make the originally complex work simpler, and at the same time, the design goals, cycle and cost will be more controllable and transparent.