Circular Slot-Based Microstrip Circularly Polarized Antenna for 2.45-GHz RFID Reader Applications

The paper presents a new design for a mobile 2.45-GHz passive Radio Frequency Identification (RFID) reader, featuring a compact, broadband, and circularly polarized antenna. The antenna proposed consists of two stacked square patches separated by an air gap for a wide-band impedance bandwidth. The antenna is printed on a double-sided 1.6 mm FR4 substrate with an overall dimension of
$65\times 65\times 11.27$
mm3. By introducing and optimizing a pair of symmetrical ring slots in both the square patches, a good Axial-Ratio Bandwidth (ARBW) and symmetrical broadside radiation patterns are achieved. The reader antenna shows a measured
$S_{11}$
bandwidth (S11<−10 dB) from (2.3–2.7 GHz) and ARBW (< 3 dB) from (2.39-2.48 GHz). The peak gain of the proposed antenna is 6.2 dBi and is obtained at the center frequency of 2.45 GHz. Measurements of the proposed antenna are discussed to obtain the read range and field of view, which confirms its suitability for RFID Reader Applications and other Internet of Things (IoT) based applications.