Figure - available from: International Journal of Antennas and Propagation
This content is subject to copyright. Terms and conditions apply.
Geometry of the proposed NFC loop antenna; (a) overall view, (b) top view printed on FPCB, and (c) side view.
Source publication
A new structure of an NFC loop antenna for mobile handset applications is proposed. The proposed antenna consists of conventional loop elements and a parasitic loop embedded capacitor to enhance its performance. Although the sintered ferrite sheets with higher relative permeability have been used to reduce the performance deterioration due to the e...
Citations
... To this end, the size of both antennas must be similar but not identical to avoid the detuning effect at short distances [42]. Modern mobiles embed the NFC antenna around the camera aperture or over the battery case, with typical sizes around 2-2.5 cm 2 [43][44][45][46]. ...
This article reviews the recent advances in the field of batteryless near-field communication (NFC) sensors for chemical sensing and biosensing. The commercial availability of low-cost commercial NFC integrated circuits (ICs) and their massive integration in smartphones, used as readers and cloud interfaces, have aroused great interest in new batteryless NFC sensors. The fact that coil antennas are not importantly affected by the body compared with other wireless sensors based on far-field communications makes this technology suitable for future wearable point-of-care testing (PoCT) devices. This review first compares energy harvesting based on NFC to other energy-harvesting technologies. Next, some practical recommendations for designing and tuning NFC-based tags are described. Power transfer is key because in most cases, the energy harvested has to be stable for several seconds and not contaminated by undesired signals. For this reason, the effect of the dimensions of the coils and the conductivity on the wireless power transfer is thoroughly discussed. In the last part of the review, the state of the art in NFC-based chemical and biosensors is presented. NFC-based tags (or sensor tags) are mainly based on commercial or custom NFC ICs, which are used to harvest the energy from the RF field generated by the smartphone to power the electronics. Low-consumption colorimeters and potentiostats can be integrated into these NFC tags, opening the door to the integration of chemical sensors and biosensors, which can be harvested and read from a smartphone. The smartphone is also used to upload the acquired information to the cloud to facilitate the internet of medical things (IoMT) paradigm. Finally, several chipless sensors recently proposed in the literature as a low-cost alternative for chemical applications are discussed.
... To this end, the size of the tag antenna should be close to that of the reader antenna, but not the same size to avoid detuning effect at short distances [39]. Modern mobiles integrate the NFC antenna around the camera aperture or over the battery case with typical sizes being about 2-2.5 cm 2 [40][41][42][43]. Taking into account the last considerations, the quality factor is limited by the IC load. ...
This work studies the feasibility of using a battery-less Near-Field Communication (NFC) potentiostat for the next generation of electrochemical point-of-care sensors. A design based on an NFC microchip, a microcontroller, and a custom potentiostat based on an operational amplifier is presented. A proof-of-concept prototype has been designed and used to quantify glucose concentration using commercial glucose test strips from chronoamperometry measurements. The device is harvested and the sensor is read using a mobile phone. The prototype uses an antenna loop covered with ferrite sheets to ensure stable operation of the electronics when the mobile phone is used as reader. The use of ferrite reduces the detuning caused by the proximity of the metal parts of the mobile phone. A comparison with a commercial glucometer device is provided. Results obtained using a commercial glucometer and those provided by the proposed potentiostat show an excellent agreement.
... The traditional approach to making the CA resonate at 13.56 MHz by simply cascading a resistance of 50 Ohm and a certain capacitance due to the standard impedance matching of 50 Ohm at the source port (as shown in Figure 1) was abandoned. However, it still has some reference values for following investigations and comparison due to its success in transmitting and receiving power at a certain frequency [10]. lectronics 2021, 10, x FOR PEER REVIEW frequency of 13.56 MHz, making it even more difficult to transmit power approach to widening the impedance bandwidth also must be under consi miniaturizing a CA. ...
... Afterwards, the Q-factor determining the efficiency energy is an important index for the whole RF system to be paid attention to a CA as small as possible with a high Q-factor is also necessary for wide im width [9]. The traditional approach to making the CA resonate at 13.56 M cascading a resistance of 50 Ohm and a certain capacitance due to the standa matching of 50 Ohm at the source port (as shown in Figure 1) was abandon it still has some reference values for following investigations and compar success in transmitting and receiving power at a certain frequency [10]. From its performance on the Smith chart in Figure 1d, the red dotted solid line represent the S-parameter of a three-turn CA with and without a cuit, respectively. ...
This paper proposes and verifies a complete design flow of miniaturizing a coil antenna and widening its impedance bandwidth for near-field application, such as NFC, RFID and WPT. The proposed scheme based on mature electronic element matching technology is interpreted in detail by two equivalent circuit models in theory. For convenience, only the series equivalent circuit and its matching circuit are respectively established in the circuit simulator ADS and ANSYS HFSS to assess the scheme proposed from two aspects. The parallel equivalent circuit can be optimized by a similar approach. Then, a WPT system is established in HFSS to further verify the feasibility of miniaturization. Finally, the dimension of the coil antenna can be reduced by about 70%, and its impedance bandwidth can be increased by approximately 40% after two electronic modules are integrated.
... [3][4][5][6] Thus, no power supply is needed in these tags, reducing the manufacture cost. Since its first introduction in early 2000s, NFC has been widely used in identification, 7 tracking, 8 access control and contactless payment systems, [9][10][11] demonstrating a key role in bringing the Internet of Things (IoTs) to reality with unimaged applications emerging every day. ...
Benefiting from the high conductivity and superb flexibility, graphene‐based materials are promising to replace metal for near‐field communication (NFC) applications. Herein, we report a flexible NFC tag antenna based on high‐conductivity graphene‐assembled films (HCGAFs) and investigate how the performance of the antenna is affected by antenna design and human body effect. The fabricated prototype via a one‐step laser‐direct mold engraving method shows a 10 dB bandwidth of 2.5 MHz centering at 13.70 MHz with a quality factor (Q) of 9.19. The maximum read range of the HCGAF NFC tag is measured to be around 7.5 cm, comparable to the commercially available metal NFC tags. Moreover, the flexible nature of HCGAFs guarantees excellent mechanical stability and deformation insensitivity, especially when compared to commercial metal‐based counterparts. We further demonstrate the practical applications of the HCGAF tag as key card and electronic business card in the vicinity of human body.
... The reader cannot, therefore, be modified, and the NFC antenna depends on the smartphone used. In modern smartphones, the NFC antenna is often integrated with a ferrite layer on top of the battery [41]- [44] in phones with plastic cases, or around the camera in phones with metallic cases [45]- [50]. As the main application is for making payments, mobile antennas are often optimized to read payment cards (standard size = 85.60 × 53.98 mm). ...
In this paper we study the read range of implanted sensors based on batteryless, Near-Field Communication (NFC) integrated circuits (IC) using an NFC-equipped smartphone as a reader. The most important challenges are the low coupling between loops of different sizes, the limited quality factor imposed by the bandwidth communication, the effects of the body on propagation, and the detuning of the antennas. Two systems are analyzed: a conventional system based on resonant coupling between two coils; and a system based on resonant coupling between three coils. With the latter, a relay antenna is attached to a patch, which is adhered to the skin. Simulations and measurements show that the quality factor of both antennas can be improved by including a spacer made of low-permittivity material. A circuit model is proposed for the implanted and relay antenna, which simplifies its usage in circuit simulators. Some implanted and relay antenna prototypes are analyzed and a system model that includes a nonlinear model of the tag is used to analyze the maximum depth at which the implant can be read. Our experimental results show that the system based on three coils performs much better performance at longer distances and is more robust to misalignments between coils. A 15×15 mm-implanted tag with commercial NFC IC and energy harvesting can be read using commercial smartphones. It can feed sensors at a distance of up to 16 mm inside the body and at a distance of 3 cm from the skin. Our results also show that data previously stored in the IC memory can be transferred to the reader located at distances of up to 2 cm and 3.8 cm for the 2-coil and 3-coil systems, respectively. This study demonstrates the potential of batteryless NFC sensors for biomedical and wearable applications using mobile phones as readers.
... In general, ferrite sheets exhibiting high permeability properties are widely implemented in conjunction with NFC antennas to mitigate undesired eddy currents [6] caused by metallic components situated above or under the loop antenna. In [7], a modified NFC loop antenna with a parasitic loop is integrated with a ferrite-polymer composite to enhance the overall physical flexibility and cost effectiveness. However, this approach becomes ineffective in situations where the loop structure is fully enclosed by a metallic frame along the horizontal plane as it is the case for majority of smartwatches. ...
This study reports methods of alleviating the effect on inductive near‐field communication (NFC) coils caused by fully enclosed metallic‐frames for wearable devices such as smartwatches. Two techniques that, respectively, involve creating two short‐circuit passages to modify the distribution of the out‐of‐phase current on the metallic‐frame and reducing the out‐of‐phase current amplitude by devising an asymmetric coil topology is presented and studied in detail. Extensive simulation, prototyping and measurement are carried out for 13.56 MHz NFC applications. The presented techniques can, respectively, improve the induced magnetic coupling by 43 and 30% under identical conditions in the presence of the metallic frame. Furthermore, both methods comply with the NFC forum certification and do not require the need to increase the drive current and power consumption of the NFC circuitry.
... To that end, an NFC antenna for shortrange communication is incorporated into modern smart devices. Thus far, a number of NFC antenna designs have been proposed [29][30][31][32][33][34]. In this research, a dual-loop NFC antenna [35] is mounted on the rear of the FF antenna (in the lower ground plane area), as shown in Figure 5. ...
This research presents a far-field (FF) antenna with near-field communication (NFC) capability for 3G/4G/LTE mobile devices. The integrated far-and near-field communication (FNFC) antenna was fabricated using conductive silver ink on polyethylene terephthalate (PET) flexible substrate. The FF segment of the antenna is operable in the frequency range of 1.8-2.1 GHz, and the NFC antenna is of dual loop and operable at 13.56 MHz. In the antenna realization, simulations were performed and, to validate, an antenna prototype was fabricated. The experimental results revealed that the FF antenna achieved an impedance bandwidth of 37% (1.52-2.21 GHz), given |S11| of less than -6 dB, with the minimum and maximum efficiency of 92.1% and 98%. The experimental gains are 1.76-2.08 dBi across the target operating frequency band, with near-omnidirectional radiation pattern. The simulation and experimental results are in good agreement. Moreover, the FNFC antenna achieves strong magnetic field distributions in Hx, Hy, and Hz orientations and holds promising potential for 3G/4G/LTE applications.
... The second case (Antenna 2, Fig. 6b) corresponds to the same antenna as Fig. 6a but with a sheet of ferrite and a metal on the bottom plane. This is a selected case because it approximates a typical solution used in mobiles with a plastic case, where the NFC antenna is located over the battery with thin ferrite foils to isolate the antenna from the metallic parts [37][38][39][40][41][42], helping to reduce emissions interference from the internal mobile circuits. It can be observed in Table II that the effect of the ferrite increases the antenna's inductance by a factor µref that depends on the magnetic permeability of the ferrite (µr) and the separation between the metal and the antenna's substrate. ...
In this paper we present a low-cost battery-less colour sensor based on Near Field Communication (NFC). This system consists of a colour sensor connected to a low-power microcontroller connected to an NFC chip. The energy needed to power up the chipset is retrieved from the magnetic field generated by the reader, i.e. a commercial smartphone. The low cost of NFC chips affords the opportunity to manufacture low-cost tags with sensing capability. We have developed a mobile application to simultaneously present the data and send them to a database in the cloud. The system has been tested with several pH reactive strips. pH was determined via colour measurement using the HSV colour space. A simple linear relationship was found between the Hue parameter and the pH. Comparison with pH determination via smartphone camera showed that accuracy was greater when the NFC colorimeter was used.
... However, generally, it is difficult to cover the 2G/3G/4G wireless communication bands completely using a single-loop structure [9]. In order to meet the bandwidth requirement, various hybrid composite structures were introduced to cover the full LTE band, including loop/monopole/dipole antenna [10], loop/open-slot antenna [11], segmented dualloop antenna [12], and dual-loop metal-rimmed antenna [7]. The objective of the hybrid combination is to add more resonant modes and to enhance the bandwidth. ...
... The external metal shell of the SMA connector is soldered to the system ground plane. [5][6][7][8][9][10][11][12]. As seen in Figure 1(b), both front ends of the proposed loop antenna are connected to the system ground plane and are capacitively coupled by the T-shaped strip. ...
A coupled-fed loop antenna with Octa-bands operation for long-term evolution (LTE) smartphones is proposed in this paper. The antenna occupies a nonground space of only 6.5 mm × 72 mm, and two wide-band operations can be achieved by exploiting the multimode characteristics of loop antenna and using high-pass matching circuits. In low band, the LTE700/GSM850/900 operation is achieved by the loop mode of 0.5 λ and matching chip capacitor which generates a dual-resonance mode at 0.74 GHz and 0.9 GHz. In high band, the 1 λ mode, the 1.5 λ mode, and the 2 λ mode of the entire loop are combined with the 0.5 λ mode of the left-side coupling loop to cover the DCS1800/PCS1900/UMTS 2100/LTE 2300/2500 operation bands. The measured average realized gains and efficiencies are approximately 1.56 dBi/2.38 dBi and 55.3%/63.6% in the two bands, and a good radiation pattern is achieved as well.
... Although the range of NFC was illustrated through their experiments, still the recovery of the data from its damaged coil was not shown. Lee et al. (2014) discussed the design and structure of NFC loop antenna for handsets. They proposed the use of ferrite-polymer composite with lower relative permeability to enhance the performance of NFC loop antenna. ...
Purpose
The purpose of this paper is to discuss a technique of restoring data from a broken/damaged near-field communication (NFC) tag whose coil is damaged and seems unrecoverable.
Design/methodology/approach
This paper discusses a method to restore data from damaged NFC tags by designing a coil that matches the technical specification of NFC for restoring information. In this paper, an NFC tag with a broken antenna coil and its operational NFC chip is used for restoring data by making an external loop antenna for the same chip.
Findings
If the NFC tag is damaged, the information stored on the tag can be lost and can cause serious inconvenience. This research provides an excellent mechanism for retrieving all the information accurately from a damaged NFC tag provided the NFC chip is not damaged.
Research limitations/implications
One of the major limitations of this research is that the NFC chip remains intact without any damages. Data can only be recoverable if just the antenna of the NFC tag is damaged; any damage to the NFC chip would make it impossible for the data to be recoverable.
Practical implications
The research is carried out with limited resources in an academic institute and hence cannot be compared to antenna designs of the industry. Furthermore, industry vendors are using aluminum to design the coil; however, in this study a copper coil is used for coil design since it is far less expensive than aluminum coil.
Originality/value
NFC is a rather new short-range wireless technology and not much work is done in this field as far as antenna study is concerned. This study brings a technique to design a coil antenna for a damaged NFC tag to retrieve all the information without losing even a single bit of sensitive information.
