In this paper, we present a novel compact, coplanar, tag antenna design for metallic objects. Electrically small antenna has designed for a UHF RFID (860–960 MHz) based on a proximity-coupled feed through. Furthermore, two symmetrical Via-loaded coplanar grounds fed by a U-shaped inductively coupled feed through an embedded transmission line. This configuration results in an antenna with dimensions of 31 × 19.5 × 3.065 mm3 at 915 MHz, and the total gain for the antenna is 0.12 dBi. The Via-loaded coplanar and U-shaped inductively coupled feeds allow the antenna to provide flexible tuning in terms of antenna impedance. In addition, a figure of merit is applied for the proposed tag antenna, and the results are presented. The read range is measured to be 4.2 m, which is very close to simulated values. This antenna measurement shows very good agreement with simulations.

In this design, a coplanar slim antenna had been proposed and designed for UHF RFID (860-960) MHz metallic objects. The slim antenna was presented with proximity coupled feeding, two symmetrical coplanar ground layers, and a transmission line fed by a U-shaped inductively coupled feed. Furthermore, the U-shaped inductive feeder consisted of two opposing symmetrical U-shaped structures to feed the top radiator of the antenna. The size of the antenna was 97.5 × 50 × 1.5 mm3 at 915 MHz. As a result, the peak gain for the antenna reached up to 5 dBi at 915 MHz. Furthermore, the bandwidth of the antenna was 24.875 MHz (900.125-925) MHz (the power reflection coefficient was lower than -3 dB), while the reading range reached up to 11 meters. Besides, the results obtained from the measurement displayed very good impedance matching due to the flexibility generated by the U-shaped inductive feeder. Moreover, the results retrieved exhibited very good agreement with the results obtained from the simulations.

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