Optimal Angle in Bistatic Measurement for Chipless Tag Detection Improvement

This article shows the use of a bistatic reading configuration by optimizing the angle between the two antennas, which allows isolating the contribution of the radio frequency identification (RFID) chipless tag from its nearby environment, thus enhancing the reading performance of the chipless tag for short-range applications. The idea is to extract as much useful signal (relating to the tag information or tag ID) from the total signal using a dedicated bistatic reading configuration. This extraction step is implemented from a hardware point of view, which is different from classical approaches based on signal processing. Indeed, based on this technique, it is possible to read tags even in highly reflective environments (metallic surfaces) without applying a calibration method, such as subtracting the environment without the tag or advanced postprocessing steps. For this purpose, a bistatic antenna configuration is employed, where the angle between the incident wave and the backscattered signal is chosen to maximize copolarization configuration. First, a model based on the general scatter theory is evaluated; it highlights the scattering mechanism involved in the problem. Then, a proof of concept (PoC) is evaluated, and afterward, a chipless tag composed of an array of dipoles is studied for identification purposes. The analytical evaluation and the channel modeling allow a general implementation of the proposed technique. Anechoic and real scenario measurements are evaluated considering the presence of surrounding objects. Finally, nonsystematic errors related to the positioning of the tag are considered each time without considering a reference (or background) measurement or the use of specific signal processing techniques.