A new chipless RF identification (RFID) tag design is presented in this paper to ease the detection of items in a real environment. For this purpose, we present multiple scatterers able to depolarize the incident wave to create a response in the orthogonal polarization. Measurements in anechoic chamber and in a real environment, when the tags are positioned on dielectric and metal objects, show their higher detection capability. For the first time, a study on the technique to increase the detection area with a simplified calibration step is carried out. This makes possible the detection of the tag on objects of various sizes and compositions, which is required in the majority of RFID applications.

This paper is mainly dedicated to the design of radio-frequency identification (RFID) tags, particularly the antennas that allow the tag to be fed, communicate, and exchange data with the reader. Good performance tags require optimized antenna that take into account numerous constraints as well as the environment of the application under consideration. Both conventional tags and robust tags are discussed. This paper also discusses how to transform a tag into an RFID sensor.

A passive harmonic tag for buried assets localization is presented for utility localization. The tag design is based on a dual-polarized patch antenna at Ultra High Frequency (UHF) band. One of its feeders is connected to a frequency doubler based on a Schottky diode that generates the second harmonic, which is transmitted using a linear-polarized patch tuned at this frequency. The power received at the other feeder of the dual-polarized antenna is harvested by an RF to DC converter based on a five-stage voltage multiplier whose energy is used to bias a low-power quartz oscillator that modulates the output of the doubler. The different parts of the system are presented, and the theoretical read range is estimated as a function of the soil composition and the water content. A low-cost reader based on a software defined radio is also presented. Finally, experiments with a prototype of the tag are performed for different soil conditions.