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We propose a new approach based on the multicarrier system, in which multiple narrowband pulses emit toward a chipless RFID tag in the UWB, to decode the tag in the time domain. The multicarrier system is known to be able to reduce complexity and interference, and also increase spectrum efficiency and flexibility. In this study, we not only experimentally investigate the backscattered signal of a frequency-coded chipless RFID tag interrogated by narrowband pulses, but we have also derived mathematical equations to describe the tag responses. We have found that the shape of the reflected response from the tag is determined by the emitted signal multiplied by a distortion factor. The distortion amount depends on transmitted signal bandwidth, tag quality factor, and resonance frequency. We further use the distorted tag response as a tag signature in the time domain for decoding purposes, eliminating the signal transformation to the frequency spectrum, which is one of the most time-consuming post-processing algorithms. To further demonstrate the performance of the proposed approach in a more realistic scenario, we have developed a customized multicarrier transceiver to decode a four-bit cross-polarized tag in the time domain. We have demonstrated that the proposed analytical approach can also enhance tag detection in a realistic environment with multiple parasitic reflections. [ABSTRACT FROM AUTHOR]

Recently, the field of flexible electronics has received significant research attention, primarily in response to the growing market for lightweight and compact devices. The low-cost mass fabrication of these flexible-electronic printed products, such as RF identification (RFID) tags, wireless sensors, conductive tags and readers, touchpads for keyboards, and display applications, all require knowledge of additive production techniques and appropriate substrates. [ABSTRACT FROM AUTHOR]

A mathematical model to characterize a frequency-coded chipless radio frequency identification (RFID) is presented. A chipless tag is comprised of multiple high-quality factor resonators. The model exploits the bandpass and band-stop characteristics of a frequency-coded tag and the channel model of the reader and tag system. The proposed model accurately reconstructs the time and frequency responses of the tag read by a reader antenna. The model is universal to any type of chipless tag. To validate the model, first, a tag is designed with CST Microwave Studio, a full-wave electromagnetic solver, and its resonant characteristic is extracted. The model is used to validate the simulation and measurement results of the same tag. Also, the tag is measured in a cluttered environment. The results show that the tag is successfully decoded in the presence of a relatively large metallic reflector to verify the robustness of the model, without any calibration. The investigation provides a comprehensive understanding of the tag and the reader system, and it is a step toward reading a chipless tag in a realistic environment. [ABSTRACT FROM AUTHOR]

Eliminating the strong self-interference signal in chipless radio frequency identification (RFID) readers is key for enabling a reliable and long range reading in chipless RFID readers. The suggested method is to add a compensation signal to cancel the leakage signal vectorially before the first stage of the receiver front-end. An ultra-wideband (UWB) polyphase power divider (PPPD) generates the vector compensation signal of any arbitrary amplitude and phase. Unfortunately, the reported PPPD cannot meet the requirements for the realization of a UWB compensation unit (CU). A microstrip wideband differential phase shifter capable of producing a wide range of phase shifts is presented in this paper. The delay lines, including transmission line (TL) segments loaded with shorted stubs (SSs), generate prescribed phase shift values with respect to the universal reference line. It is shown that an arbitrary phase shift (up to 360°) with an in-band return loss (RL) better than 15 dB within an octave bandwidth is obtainable. Its full-range phase shift capability alongside the universal reference line and simple structure ensure its suitability for polyphase applications. To verify the proposed structure, a set of C-band phase shifters ranging from 60° to 300° is designed and fabricated, and a phase deviation from ±1° to ±9° is obtained. Finally, based on the proposed differential phase shifter, a four-phase power divider is implemented and utilized in the CU of a chipless RFID reader. Excessive isolation of better than 35 dB over 4–8-GHz frequency band is attained. [ABSTRACT FROM AUTHOR]

RF identification (RFID) is a well-known wireless technology that has emerged for capturing data from a stationary or dynamic object. This is one of the key technologies poised to replace barcodes, which are low in data capacity and difficult to reprogram. To address this storage-of-data limitation, the silicon RFID chip was developed. Auto ID-based technologies such as optical barcodes and RFID address the function of "contactless" behavior, which eliminates the impracticalities of mechanical touch and enables the performance of defined tasks. [ABSTRACT FROM AUTHOR]

Radio frequency identification (RFID) tags are highly sensitive to material contents of the tagged objects, especially with liquids and metals. The presence of an attached object on the tag can be detrimental for tagID detection. In this study, the RF performance of chipless RFID tag placed on different commercial objects for identification purpose is comprehensively analysed. Probable solutions are proposed for observed issues to make the chipless RFID tags readable on various items such as non-conductive objects, liquid containers and metal items. The misalignment between the reader antenna and the tag is another issue during the commercial implementation of chipless RFID system. A tri-planar positioning of the tag has been verified as an appropriate solution in this study. The chipless tag has the potential to read stacked pallets and boxes with liquid/solid contents in warehouse scenarios using the proposed solutions. [ABSTRACT FROM AUTHOR]

In this paper, a passive radio-frequency (RF) sensor has been presented for non-invasive radiometric detection of simultaneous partial discharge (PD) signals in high-voltage (HV) equipment. The sensor is a multi-resonator-based passive circuit with an antenna for capturing PD signals. The low-cost RF sensors are installed in HV sensing units for monitoring multiple units simultaneously. Each sensor captures PD signal and processes it with distinct spectral signatures as identification data bits and transmits the signal to a single sampling channel. From the captured RF signal, both the PD level and the source identification can be retrieved. Our proposed passive sensor addresses both aspects of PD monitoring, PD detection, and faulty source identification. Moreover, in identifying the data bits, the time–frequency analysis is utilized for superior detectability. This analysis enables the detection of multiple PD events separated by a defined time delay, although they occur at the same instance. Thus, the sensor can distinguish simultaneous PD occurrences from multiple sources, which is a novel contribution in PD detection. The proposed sensor system provides low-cost, passive condition monitoring of HV units in a distribution substation. [ABSTRACT FROM PUBLISHER]

Ultra wide band (UWB) impulse radio (IR) technology has different applications in different sectors such as short range radios and collision avoidance radar. A strong signal denoising method is needed for UWB-IR signal detection. One of the challenges of UWB-IR signal detection technique is the environmental interferences and noises. Wavelet Packet Transform (WPT) based multi-resolution analysis technique is suitable for this kind of signal denoising and detection. The paper describes a better method of denoising and detection technique of UWB-IR signal based on calculation of energies of the coefficients of each WPT terminal-node and by using an improved threshold calculation technique. The proposed technique is investigated through both simulation and experimentation. [ABSTRACT FROM AUTHOR]

Entering ?RFID? on your Web browser will return you more than 50 million links. This huge number of references is a result of the impact of radio-frequency identification (RFID) technology worldwide [1]. Indeed, RFID technology is exploited in numerous domains, with thousands of applications, including more and more seen in everyday life. The RFID market is worth several billion dollars today, and its growth is more than 10% per year [2], [3]. There are two main classes of RFID devices. Figure 1 illustrates the main features of each class. The most known and broadly used class is the one based on the use of an integrated circuit (IC) chip in which the information is stored and that is connected to an antenna; the two together form the ?tag.? Such a technology exhibits several advantages, including flexibility and versatility in terms of the application. Nevertheless, it has some drawbacks mostly in terms of cost, robustness, reliability, data security, and poor recyclability of tags. More properties and new functionalities, such as sensing capabilities and tag-totag communication [4], are continually being developed, leading to the new paradigm of Internet of Things [5]. [ABSTRACT FROM PUBLISHER]

A very low-cost RFID reader architecture comprised of a voltage-controlled oscillator (VCO), a mixer, and a low-pass filter (LPF) for reading an ultra-wideband chipless RFID tag is proposed. The VCO generates a linear chirp (swept) frequency interrogation signal. The reader, which is a coherent frequency-modulated continuous-wave radar, interrogates a tag and decodes the tag's identification data in both amplitude and phase information. A signal-processing technique based on Hilbert transform (HT) is used and accurate detection of a 9-b tag is achieved. The new reader needs only one VCO and does not need any calibration tag to decode data as needed for its predecessors. [ABSTRACT FROM PUBLISHER]

A fully passive printable chipless RFID system is presented. The chipless tag uses the amplitude and phase of the spectral signature of a multiresonator circuit and provides 1 : 1 correspondence of data bits. The tag comprises of a microstrip spiral multiresonator and cross-polarized transmitting and receiving microstrip ultra-wideband disc loaded monopole antennas. The reader antenna is a log periodic dipole antenna with average 5.5-dBi gain. Firstly, a 6-bit chipless tag is designed to encode 000000 and 010101 IDs. Finally, a 35-bit chipless tag based on the same principle is presented. The tag has potentials for low-cost item tagging such as banknotes and secured documents. [ABSTRACT FROM AUTHOR]

The development of a low-cost backscattered semi-active Radio Frequency Identification (RFID) tag that works in 2.4 GHz frequency band is presented in this study. The tag comprises of an annular ring slot antenna, a feed with a matching network, a Schottky diode modulator and a microcontroller with an in-built oscillator. The tag is powered by a 3 V pill-box battery and uses amplitude shift keying (ASK) modulation to communicate its identity to the tag reader. Results presented include the performance of the slot antenna, the feed network, the associated software and identification of the tag in real time by a Hyper-X® reader. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007. [ABSTRACT FROM AUTHOR]

Novel defected ground structures (DGSs) have been investigated to achieve improved low-pass filter (LPF) properties. A chronological development in designs ranging from conventional square-patterned photonic-bandgap structure (PBGS) and conventional dumbbell-shaped DGS to proposed novel nonuniform DGS has been investigated theoretically and experimentally using computer-aided design (CAD) tools. It can be seen that the proposed novel DGS having Chebyshev distribution provides excellent performances in terms of ripples in the passband, 10-dB return-loss bandwidth (RL-BW), and 20-dB rejection bandwidth, as compared to conventional DGSs and PBGSs. Thus, a perturbed surface below a standard 50Ω microstrip transmission line provides LPF characteristics. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005. [ABSTRACT FROM AUTHOR]

The design and development of a compact receiver front-end comprised of two even-harmonic direct-conversion mixers, a quadrature hybrid coupler, two bandpass filters, two lowpass filters and a Wilkinson power divider are presented. The subharmonic mixer utilizes a well-matched antiparallel diode (APD) pair. The design helps improve the 2nd-order intermodulation performance (IM2) due to the suppression of the even-order mixing products and LO noises. The receiver front-end is able to generate in-phase I and quadrature-phase Q baseband outputs at 35 MHz. The detailed design of radio frequency (RF) components at the C-band and a quadrature intermediate frequency (IF) carrier signal in the I and Q waveforms are demonstrated successfully with a 9-dB effective IF conversion loss at 10-dBm LO power at the C-band. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005. [ABSTRACT FROM AUTHOR]

A dual-band dual-feed planar inverted-F antenna (PIFA) is tuned with its physical parameters. It is demonstrated that the corner truncation of the patch is less sensitive to the resonant frequency than the patch lengths, but the corner truncation has no adverse effect on the radiation characteristics of the PIFA. This new technique yields quicker convergence of design frequency than the conventional patch length only tuning. Both theoretical and measured results of the input return loss and radiation patterns are presented. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 345–349, 2001. [ABSTRACT FROM AUTHOR]