Mohammad Zomorrodi

Novel MIMO-based technique for EM-imaging of chipless RFID

A novel MIMO-based technique is proposed for fast data decoding of a printable chipless RFID tag through SAR-imaging approach. The tag includes an array of 45° inclined conductive meander line polarizers. Reader comprises a set of fixed MIMO-based Tx and Rx antennas resulting in a long virtual array antenna. Synthetic aperture radar (SAR) image processing through the MIMO-based antennas provides a fast approach for electromagnetic (EM) imaging of the RFID chipless tag that reveals the encoded data. Provided EM-image resolution yields 17-bit data from a tag of one fifth of a credit card size. Therefore, encoding of 93 data bits is feasible in a credit card. The tags immunity to multipath, reflective surfaces, interferences, bending effects and printing inaccuracies along with its high data capacity attributes huge potentials for low cost item tagging.

Cross-RCS based, high data capacity, chipless RFID system

A fully printable 60 GHz chipless RFID tag provides high data capacity. The printed tag consists of an array of 45° inclined conductive microstrips that act as perfect electromagnetic (EM) polarizers. When illuminated with a linearly polarized signal, the tags backscattered cross - radar cross section (RCS) response is much larger than its co-RCS. The tag can encode up to 50 bits of binary data in a small area of 100 mm ×6 mm. The tag is immune to multipath, interferences and printing inaccuracy.

An array of printed dipoles at 60 GHz

An array of four printed dipole antennas is developed at 60GHz for Image-based chipless RFID application. The dipoles are built on both sides of the Takonic TLX-8 (εr=2.55) and fed through a Co-planar waveguide (CPW) line. The total array dimension including its long feed line is 24×14 mm. An excellent wide radiation pattern in the azimuth direction is tested. The measured gain of the array is between 5.5 and 7 dBi over the frequency range of 57-64 GHz and the cross-polarization ratio is less than -18dB. The printable structure, wide radiation pattern, low return loss, wide bandwidth and high cross-polarization ratio of the proposed array suggest it as a suitable antenna for many applications in mm-wave range including chipless RFID systems.

Introduction of electromagnetic image-based chipless RFID system

All available techniques in chipless RFID systems are suffering from low data capacity. In this paper electromagnetic imaging technique in mm-wave range is proposed to enhance low data capacity of chipless RFID tags. It is shown through simulation that the diffraction of electromagnetic waves by a well oriented narrow conductive strip suggests a reliable approach for data encoding in the proposed technique. The proposed technique is capable of coding 2 bit/cm2 in only 100 MHz of frequency bandwidth. Synthetic Aperture Radar technique is also proposed to provide a high resolution image and solving the problem of farfield limitation of the reader antenna.

Advanced chipless RFID: MIMO-based imaging at 60 GHz-ML detection

The book proposes new approaches to chipless RFID tag encoding and tag detection that supersede their predecessors in signal processing, tag design, and reader architectures. The text is divided into two main sections: the first section introduces the fundamentals of electromagnetic (EM) imaging at mm-wave band to enhance the content capacity of Chipless RFID systems. The EM Imaging through Synthetic Aperture Radar (SAR) technique is used for data extraction. The second section presents a few smart tag detection techniques for existing chipless RFID systems. A Multiple-Input and Multiple-Output (MIMO) based tag detection technique improves the spectral efficiency and increases data bit capacity. The book concludes with a discussion of how the MIMO approach can be combined with the image based technique to introduce a complete solution with a fast imaging approach to chipless RFID systems. The book has the following salient features:

On the study of fabrication errors on mm-wave antenna

The process for design and fabrication of a planar antenna at 60 GHz frequency band is reviewed. The factors affecting the antenna performance are considered. A sample planar array antenna including four Double side printed dipoles is investigated for occurred errors during fabrication. The antenna is robust toward process variation and shows satisfactory input impedance. The described design process provides a reliable approach for other planar antennas at mm-band.

Optimized MIMO-SAR Technique for Fast EM-Imaging of Chipless RFID System

Spatial diversity cross-polar approach to fast electromagnetic imaging of millimeter-wave chipless radio-frequency identification (RFID) tags is proposed. Slow imaging in the synthetic aperture radar (SAR) technique due to the moving reader antenna is replaced by a stationary multiple-input multiple-output (MIMO) array antenna. The proposed MIMO technique requires a large number of antenna elements, which impedes practical implementation of the reader. An optimized MIMO system through a genetic algorithm halves the number of antenna elements and successfully replaces the conventional SAR. The optimized antenna system combines with the original spatial diversity approach to provide a low-cost solution for chipless RFID tagging with enhanced content capacity. The system successfully decodes a 60-GHz 17-b chipless tag in an area that is one fifth of a credit card. The tag can be printed with a low-resolution printer and read on metal and liquid containers.

Chipless RFID Reader: Low-cost wideband printed dipole array antenna.

Millimeter waves centered at 60 GHz are severely absorbed by oxygen (15-20 dB/km) and, therefore, are not suitable for long-range communication. However, this band provides a unique frequency sharing and interference-free condition for short-range communications. This unlicensed band also benefits from the generous global regulatory freedom condition. Therefore, the 60-GHz band is nominated as an ideal candidate for the high-data density applications by the International Telecommunication Union.

On the usage of diffraction effect for chipless RFID systems

Diffraction of electromagnetic wave by a conductive strip on a dielectric slab is studied through Kobayashi potential technique. The strip is designed to maximize the cross-component of the backscattered signal hence the conductive strip performs as an EM-polarizer. This characteristic is been utilized at the radio frequency identification (RFID) system to propose a chipless tag structure with enhanced data encoding capacity.