UHF Band Rfid Reader Antenna Design And On-Chip Inductors Research

Contents of this paper include two aspects:UHF band RFID near-field reader antennas design and millimeter wave bands on-chip spiral inductors re-search.In the UHF band, there are some challenges for near-field reader antenna design:(1) As for near field antenna, One of the challenges in UHF near-field RFID applications is to design reader antennas with small-size, strong near magnetic fields and low gain simultaneously.(2) Large size antenna require-ments for applications, such as smart shelves field. The difficulty lies in the de-sign:all-metal magnetic shelf application environment will affect the distribu-tion of the antenna; difficult to achieve over a wide size range uniform distribu-tion of the magnetic field causing the reading nulls, it is difficult to meet the ap-plication requirements.Based on the above analysis, this paper proposed two UHF band near-field reader antennas.(1) A novel antenna using dual S-shaped micro-strip lines are proposed. The measured bandwidth is174MHz (819MHz-993MHz) under the condition of VSWR less than2. The antenna achieves good impedance matching and uniform magnetic field distribution over the entire UHF RFID band (840MHz-928MHz). The measured reading distance is70mm and no reading nulls are detected by using the Impinj UHF near-field button. The far-field gain is lower than-7dBi.(2) Bending-wire antenna can be applied to intelligent shelves system. The antenna can work in all-metal environment stably.On the other hand, in order to meet the design requirements of designs at millimeter wave band, the inductor must have a high self-resonant frequency and a high Q value at the required frequency band. Thus, the design of millime-ter wave high-Q inductor is the key to improve the performance of silicon-based millimeter wave systems. In this paper, a60GHz on-chip spiral inductor based on CMOS technology is simulated. The inductance simulation results are as follows:when the fre-quency is in the range of30GHz-80GHz, the inductance value is between114pH and130pH, the Q value is17.8, and the self-resonant frequency is about185GHz, able to meet the design requirements. In addition, the π equivalent cir-cuit model and T equivalent circuit model of the inductor has been build.