Design of electrically small, folded monopole antenna using C-shaped meander for active 433.92 MHz RFID tag in metallic container application

A miniaturised RFID tag antenna for an active 433.92 MHz RFID system was designed, fabricated and measured. To attain a low profile, a folded monopole was bent and matched with a stub like an inverted-F antenna. Then the horizontal radiating segment was miniaturised with a C-shaped meander. The height of the antenna from the ground plane was 20 mm (0.029λ) and the antenna can be enclosed in a circle with a diameter of 34 mm (0.049λ). The measured 210 dB fractional bandwidth was 3.52 MHz (0.81%) and the measured gain showed a conical radiation pattern with a maximum gain of 21.33 dBd.