We consider chipless tags, which are based on Latin letters and also legible, for radio-frequency-identification (RFID) applications. Since letters using standard fonts have relatively weak and smooth responses with respect to frequency, special slits are designed to improve the distinguishability of letters without sacrificing their legibility. The designed set of letters can be used to generate words that are also suitable for RFID applications with their strong and unique scattering characteristics. The tags are fabricated via low-cost inkjet printing, making them both flexible and inexpensive.

Using embedded microchips on radio-frequency identification (RFID) tags requires difficult mounting processes and increases the tag price. Therefore, chipless RFID tags have been introduced in the literature. In this paper, an improved series of chipless RFID letter-type tags are introduced. Each letter has unique characteristics that can be identified clearly, thanks to the well-designed slits opened to improve its electromagnetic response without sacrificing legibility. Simulations are realized for 150-point Calibri letters, which are also suitable for low-cost inkjet printing, excited with different polarizations. Various types of slits are investigated on the letters to achieve more reliable identification of the corresponding tags. A comparative analysis based on backscattered radar cross section and current distribution results is presented.

In this study, a new practical method for fast fabrication of low-cost wearable antennas is introduced. The antennas are directly cut from woven conductive fabrics, while their terminals are connected to microchips by using a repair glue. Following simple trials to demonstrate the fabrication procedure, high-performance radio-frequency antennas that are suitable for the proposed method are designed in a simulation environment based on the multilevel fast multipole algorithm and genetic algorithms. Simulations and measurements on fabricated samples demonstrate very good agreement, showing the feasibility of low-cost, lightweight, flexible, and wearable antennas to be fabricated via the proposed approach.

The authors present cage-dipole antennas that are suitable for inkjet printing. The antennas involve hard-coded switches, i.e. open and closed gaps, for providing desired antenna characteristics at radio frequencies. Optimisations are performed rigorously using the method of moments (MOM) or the multilevel fast multipole algorithm (MLFMA) combined with genetic algorithms to find the most suitable switch configurations. Thousands of trials required for the optimisations are performed accurately and efficiently using MOM/MLFMA without resorting to alternative representations of the antennas. Optimised antennas are further fabricated via low-cost inkjet printing. Inkjet-printed cage-dipole antennas, as well as the overall design and fabrication procedure, are suitable for radio-frequency applications that require inexpensive and easy-to-produce antennas.

We present design and computational analysis of log-periodic antennas that are fabricated by using low-cost inkjet printing technology. The designed antennas operate in the 1.5-2.5 GHz range and are suitable for diverse applications, including energy harvesting at WiFi and GSM bands. Suitable designs are fabricated by using silver-based inks in standard commercial printers. Despite the challenges in both design and fabrication processes, we demonstrate log-periodic antennas with desired operating properties at the target frequencies. Details of the design procedures, parametric analysis, as well as simulation and measurement results are presented.