Optimum Separation for Performance Improvement of RFID Solenoid Coil Antenna in Metallic Environments

A metal pipe is a key factor affecting the performance of the oil well downhole radio frequency identification (RFID) system. This letter investigates the optimum separation for coping with the impact of metal pipe on the solenoid coil antenna so as to improve the performance of the downhole RFID system. Through the equivalent circuit model of RFID communication, a new objective of maximizing the reader antenna inductance is introduced from the perspective of demodulating the tag data easily. Then, a small optimum separation with a large antenna diameter is given out by the electromagnetic simulation of solenoid antenna in the metal pipe, which could not only ensure the trafficability of tag ball and decrease the tag speed in the antenna area but also reduce the minimum magnetic field required for the reader to read the tag. Finally, the calculation of optimum separation is compared with that of the experimental test and shows good agreement.