Design of Near-Field Edge-Shorted Slot Microstrip Antenna for RFID Handheld Reader Applications

In this letter, a compact edge-shorted slot microstrip antenna with good near-field performance for radio frequency identification (RFID) applications is proposed. It is composed of a rectangular slot radiator, a shorting wall, and a pair of shorting strips, which occupy a small size of 40 (L)×16 (W)×6 (H) mm³ to be easily embedded inside a handheld reader device as an internal antenna. By properly designing a thin slot and a shorting wall, strong and uniform electric field distribution surrounding the near-zone region can be obtained with the antenna. This design can not only achieve an operating band of 2.38-2.55 GHz, but also generate large capacitive coupling effect to significantly enhance the near-field performance for actual application. Experiments exhibit that the proposed patch antenna may well function as a handheld reader antenna to detect the dipole-like tags through capacitive coupling for RFID near-field operation.