Maher Khaliel

UWB Reflectarray Antenna for chipless RFID applications

The main limitation of any chipless Radio Frequency Identification (RFID) system is the very short reading range. In this paper, we propose an Ultra Wideband (UWB) Reflectarray Antenna (RA) system with 2.2 GHz bandwidth centered at 6 GHz for the reader of chipless RFID applications. The proposed reader antenna system enhances reader sensitivity, reduces multipath effects, helps in tag localization and a lot of novel capabilities that cannot be provided by the conventional antenna systems. The cell used in the design is the double circular ring where the antenna panel consists of 100 elements (10×10). Simulations show that the proposed antenna system reaches fractional bandwidth (FBW) 37% covering all the feeder bandwidth. This achieved ultra wide bandwidth (UWB) satisfies the requirements of the frequency signature based chipless RFID systems.

Novel notch modulation algorithm for enhancing the chipless RFID tags coding capacity

The main objective of this contribution is to introduce a novel technique for increasing the coding capacity of the Frequency Coded (FC) chipless RFID system. The proposed scheme encodes 4 bits per single resonator exploiting the notch bandwidth and its corresponding frequency position. Hence, 72-bits could be achieved from 2 to 5 GHz preserving the operating frequency bandwidth. Furthermore, a Smart Singular Value Decomposition (SSVD) technique is utilized to estimate the notch bandwidth and ensure low probability of error. Consequently, high encoding efficiency and accurate detection could be achieved with simplified reader design. Likewise, a novel 4 × 5 cm2 tag is designed to fit the requirements of the devised coding technique. Different tag configurations are manufactured and validated with measurements using Software Defined Radio (SDR) platform. The introduced coding methodology is conclusively validated using Electromagnetic (EM) simulations and real world testbed measurements.

Novel Pseudo-Noise coded chipless RFID system for clutter removal and tag detection

In this contribution a novel Frequency Coded (FC) chipless RFID system is introduced to significantly enhance the tag detection. The proposed system exploits the properties of Pseudo Noise (PN) random sequence, as a transmitted signal, to accurately estimate the Channel Impulse Response (CIR). Consequently, the undesired environmental clutter is filtered by a Selective-RAKE receiver. Hence, the tag is accurately identified in a heavily dense multipath environment using neither reference tags for calibration nor the non-practical no-tag deduction process. A real world simulation, based on ray-tracing tool is performed for to verify the system performance. Furthermore, the system testbed is realized on Software Defined Radio (SDR) platforms, where the tag detection is achieved with minimum latency and optimal precision.

A novel co/cross-polarizing chipless RFID tags for high coding capacity and robust detection

The aim of this work is to introduce a novel tag design enhancing the coding efficiency for the Frequency Coded (FC) chipless RFID system. The proposed approach relies on exploiting the backscattered co/cross-polarized signals from a tag excited with a linear-polarized wave. Consequently, the tag signature is encoded into Notch/Peak (N/P) format in two orthogonal planes. Furthermore, the introduced tag design exhibits narrow resonance bandwidth ensuring best utilization of the operating frequency range and sufficient coding capacity with compact tag size. Hence, 80-bit coding capacity is reached employing physical amplitude On Off-N/P (OO-N/P) modulation and N/P-Position (N/P-P) modulation principles. The presence or absence of a resonator resembles the OO-N/P modulation while the shift in the frequency position imitates the (N/P-P) modulation. In addition, the depolarization property increases the probability of tag detection in a real-world heavily dense multi-path environment. An asymmetry crossed dipole structure is employed to facilitate coding in both divergent polarities separately. The manufactured tags are verified in indoor real-world environment to proof the robustness of the introduced tag design and encoding algorithm. In the full paper, various parameters such as reading range, tag miniaturization and angular stability will be investigated.

Wideband hybrid analog-digital beamforming massive MIMO systems based on Rotman lens

Hybrid analog-digital beamforming is a well-known cost-efficient signal processing method for massive MIMO systems. In this paper, we propose a hybrid beamforming massive MIMO system based on Rotman lens analog beamforming with beam selection and digital beamforming. Rotman lens is a true-time delay analog beamforming network supporting wide bandwidth signals, which is thus more attractive than the analog beamforming networks based on traditional narrow-band phase shifters. Hence, the performance of the proposed system is investigated and verified experimentally. In particular, we design and fabricate a sample of Rotman lens operating in 5 GHz band, whose measured performance agrees well with the computer simulation. To optimize our hybrid beamforming system in terms of error-rate performance, a low-complexity greedy beam selection algorithm is proposed. Our measurement and simulation results on the error-rate performance show that the hybrid beamforming system based on Rotman lens has a wide bandwidth and exhibits superior performance over the small-scale MIMO system under the same number of RF transceivers.

Novel adaptive sliding window algorithm reducing latency for multi-tag chipless RFID systems

The main contribution of this work is to introduce a novel technique for reducing the latency of multi-tag Frequency Coded (FC) chipless RFID systems, which is defined as the time required for the reader to identify the tagged objects within the same interrogation zone. The frequency scanning methodology, windowing and notch detection are the three main processing blocks that significantly affect the overall system latency.

Adaptive spectrum scanning techniques for reducing the identification time of the frequency coded chipless RFID system: Adaptive spectrum scanning techniques for reducing the identification time of the frequency coded chipless RFID system

The main objective of this contribution is to introduce novel techniques for reducing the time taken from the reader to identify the frequency coded chipless radio frequency identification tags existed in the reader’s interrogation region, system latency. The frequency scanning methodology, number of averaging for clutter removal, and hop duration are the 3 main parameters that significantly affect the overall system latency. Consequently, the adaptive frequency hopping (AFH) and adaptive sliding window (ASW) methodologies are proposed and proofed to be efficient for the chipless radio frequency identification systems from the latency and accuracy perspectives. Likewise, the performance of the designed AFH and ASW techniques are compared with the classical fixed frequency hopping methodology with a fine frequency step to validate the accuracy of the proposed methods. Moreover, 4 different coded frequency coded chipless tags are manufactured and used in the measurements. A real-world testbed is designed including a software-defined radio platform by which the proposed adaptive algorithms and traditional fixed frequency hopping methodology are implemented. All the measurements are performed in an indoor realized scenario, including the environmental effects. The experiments show that the proposed AFH combined with ASW algorithms significantly reduce the system latency by 58%.

Rotman Lens Based Hybrid Analog–Digital Beamforming in Massive MIMO Systems: Array Architectures, Beam Selection Algorithms and Experiments

Hybrid analog-digital beamforming is a well-known cost-efficient signal processing method for massive MIMO systems. In this paper, we propose a hybrid beamforming massive MIMO system based on Rotman lens analog beamforming with beam selection and digital beamforming. Rotman lens is a low-cost true-time-delay analog beamforming network supporting wide bandwidth signals, which is thus more attractive than the analog beamforming networks based on conventional high-cost phase shifters. To study our system based on Rotman lens, we first examine two potential array architectures, i.e., full-array and subarray architectures, concerning the RF design feasibility, insertion loss, and system scalability. Since the beam selection is required in our system, we propose two beam selection algorithms, i.e., greedy search-based method and branch- and bound-based method, aiming to optimize the hybrid beamforming system in terms of error-rate performance for both the full-array and subarray architectures. To validate our system in practice, the proposed system is also investigated and verified experimentally. In particular, we design and fabricate a sample of Rotman lens operating in the 5-GHz band, whose measured results agrees well with the computer simulation results. The measurement results are incorporated into the Monte-Carlo simulation with the proposed beam selection algorithms to study the error-rate performance. Our simulation results show that the hybrid beamforming system using the low-cost Rotman lens has performance comparable to that of the system using the high-cost phase shifters, and exhibits wideband capability and superior performance over the small-scale MIMO system under the same number of RF transceivers.

Real-world testbed for multi-tag UWB chipless RFID system based on a novel collision avoidance MAC protocol

Chipless radio frequency identification RFID tags are dummy, memoryless, with limited number of bits, very low backscattered power, and short reading range. Therefore, the existing RFID standards and protocols designed for the chipped RFID systems are not applicable for the chipless systems. Main objective of this contribution is to introduce a novel real-world testbed for multi-tag ultra-wideband UWB chipless RFID system. In this testbed, a new Notch Position Modulation scheme is implemented as the first medium access control algorithm for handling the multi-tag identification scenario of the frequency signature based chipless RFID tags. This intelligent Notch Position Modulation algorithm reduces the sensing and identification time and accordingly the overall system latency. The proposed protocol enables fetching the frequency signatures of the chipless RFID tags through the whole UWB range effectively. Moreover, an advanced signaling scheme is designed for the RFID reader in order to make the best use of the Federal Communications Commission UWB regulations for increasing the maximum transmitted power and the corresponding reading range. The signaling scheme, real-time channel estimation, and clutter removal technique are implemented on the software defined radio platform in a heavily dense multipath indoor environment. Based on the medium access control protocol, the mitigation of the undesired environmental reflections as well as the interference between the chipless RFID tags is well demonstrated in the developed testbed.

Design an adaptive electronically beamsteering reflectarray antenna for RFID systems

The main objective of this paper is to design an electronically scanning reflectarray antenna for the RFID system to precisely identify and locate the tags. The RA consists of a novel cell design utilizing a varactor diode to provide the phase shifts required to steer the beam in a certain direction. The cell used in the design is Split Slotted Dipole (SSD) that provide minimum re-radiation loss and sufficient phase range and phase slope. The achievable phase range is 300° over the frequency range from 4.8 GHz to 5.9 GHz. Finally, we achieved a steerable directive beam with a beamwidth of 16° from -65° to +65° with low Side Lobe Level (SLL) and a considerable high gain from 14 dB to 17 dB over the operating frequency range.