A Novel Printable Tag of M-Shaped Strips for Chipless Radio-Frequency Identification in IoT Applications

There is a growing interest in chipless radio-frequency identification (RFID) technology for a number of Internet of things (IoT) applications. This is due to its advantages of being of low-cost, low-power, and fully printable. In addition, it enjoys ease of implementation. In this paper, we present a novel, compact, chipless radio-frequency identification (RFID) tag that can be read with either vertical or horizontal polarization within its frequency bandwidth. This increases the sturdiness and detection ability of the RFID system. In addition, the difference between the vertical and horizontal responses can be used for tag identification. The proposed tag uses strip length variations to double the coding capacity and thereby reduce the overall size by almost 50%. It has a coding capacity of 20 bits in the operating bandwidth 3 GHz-7.5 GHz, and its spatial density is approximately 11 bits/cm(2). The proposed tag has a 4.44 bits/GHz spectral capacity, 2.44 bits/cm(2)/GHz encoding capacity, a spatial density at the center frequency of 358.33 bits/lambda(2), and an encoding capacity at the center frequency of 79.63 bits/lambda(2)/GHz. A prototype is fabricated and experimentally tested at a distance of 10 cm from the RFID reader system. Then, we compare the measured results with the simulations. The simulated results are in reasonable agreement with the simulated ones.