Advanced Chipless RFID

CHAPTER 7FAST IMAGING THROUGH MIMO-SAR

7.1 INTRODUCTION

Providing a fine spatial resolution on the chipless RFID tag surface through the millimeter-band 60 GHz and synthetic aperture radar (SAR) technique has been introduced earlier. While the proposed technique benefits from many practical features, there are two main issues that deter its full potentials. The requirement for relative movement of the reader and tag is recognized as the most crucial limitation of the proposed technique. Moreover, the tag orientation sensitivity is also associated with the proposed technique, while a practical solution has been suggested in the previous chapter. This chapter considers the requirement for movement of the reader and a practical solution with reasonable hardware complexity is suggested.

The general structure of the proposed technique based on the conventional SAR technique is shown in Figure 7.1. The reader, including its two orthogonally oriented antennas, moves around the tag and captures the backscattered signal at different view angles. The total synthetic length depends on the reading range, required image resolution, and the tag data capacity. However, as shown in the previous chapters, the maximum length of 30 cm is enough to provide 0.5 image resolution when the tag has its maximum length, 8.5 cm. The interval between each two adjacent transmit and receive antennas also depends on the wavelength. Normally, 2 mm is selected as the physical separation between two transmissions ...