Universal Ultra-high-frequency Research Articles

A universal UHF near‐field RFID reader antenna with wide bandwidth and adjustable reading area

AbstractA universal ultrahigh‐frequency (UHF) near‐field radio‐frequency identification (RFID) reader antenna with wide bandwidth and adjustable reading area is proposed in this letter. The antenna consists of an inverting power splitter base on double‐sided parallel stripline and adjustable traveling‐wave near‐field radiation units, which consists of two symmetrical meander microstrips and a complementary open resonant ring loaded on the ground plane. A design example with three radiation units is simulated, fabricated, and tested for verification. The result indicates that the proposed antenna has the 10‐dB impedance bandwidth of 128%, which completely covers the universal UHF RFID band from 840 to 960 MHz. The 100% read–write rate is achieved within the read–write distance of 10 mm according to the reading test. The reading area of 731 × 120 mm2 can be obtained for increasing the number of radiation units to 10. Moreover, the antenna features low far‐field gain, low‐cost, strong and uniform magnetic field distribution. Therefore, the proposed antenna and design method have good application prospects in the Internet of Things.

Backfire suppressed low profile aperture coupled stacked patch antenna backed by a high impedance surface (HIS) reflector for UHF RFID reader applications

In this paper, a backfire suppressed aperture coupled circularly polarized (CP) stacked patch antenna for universal ultra-high frequency (UHF) radio frequency identification applications is presented. Cross-polarized backfire radiation patterns were successfully suppressed by a planar high impedance surface (HIS) reflector. The size of the fabricated antenna is 250 × 250 × 26.9 mm3 (0.71λ0 × 0.71λ0 × 0.076λ0) and its peak gain value of 7.1 dBi is measured. The distance between the antenna and the HIS reflector is only 4.8 mm (0.014 λ0). The HIS reflector suppressed cross-pol backfire radiations by about 10 dB. Detailed antenna and HIS reflector design are discussed thoroughly in this paper. The presented backfire suppression technique using the HIS reflector is scalable to other applications and frequency bands. This paper demonstrates the feasibility of the HIS structure at UHF band.

Compact wideband circularly‐polarized antenna for universal UHF RFID handheld reader

AbstractA compact wideband circularly‐polarized (CP) RF identification (RFID) handheld reader antenna based on inverted‐F antennas (IFAs) is proposed. The antenna consists of an upper layer of rotationally symmetric radiation structure and lower layer of feed network. Firstly, the feed network is verified by microwave circuit simulation software. Then the antenna is modeled and simulated with the aid of the full‐wave electromagnetic simulation software. Finally, a prototype is fabricated using FR4 plate and its performance of the proposed antenna is validated. The measured impedance bandwidth of 10 dB and the axial ratio (AR) bandwidth of 3 dB are wider than 13%. The peak gain is greater than 2.2 dBic, and the minimum AR is less than 1.1 dB, with the symmetrical and stable radiation patterns. The antenna has the compact size of 60 × 60 × 15 mm3. The proposed antenna can not only meet the requirements of RFID handheld reader applications in universal ultra‐high frequency (UHF) band (840‐960 MHz), but also has the advantages of wideband, small size, lightweight, low cost, and simple structure. Therefore, the design has a good application prospect in the field of Internet of Things.

A Novel Compact CP Antenna with Wide Axial Ratio Bandwidth for Worldwide UHF RFID Handheld Reader

This study presents a novel compact circularly polarized antenna for universal ultrahigh-frequency (UHF) radio-frequency identification (RFID) handheld reader applications. The antenna is composed of a coplanar waveguide (CPW) L-shaped feedline mounted at the right edge of the square slot at the bottom of the ground plane to realize a circular polarization; a horizontal stub protruded from the right side of the square slot towards the slot centre, and a vertical stub is mounted at the lower left of the square slot. The designed antenna printed on one ground plane layer of a low-cost FR4 substrate with an overall size of 120×120×1.6 mm3. The measurement results show indicate that the fabricated antenna achieves a wide axial ratio (AR) bandwidth of 460 MHz (818–1278 MHz), wide impedance bandwidth of 54.6% (630–1103 MHz), and a measured peak gain of 4.0 dBi. The proposed antenna is a good candidate for compact universal UHF RFID handheld reader applications (840–960 MHz).

Compact broadband dual‐band circularly polarised antenna for universal UHF RFID handheld reader and GPS applications

This study introduces a simple, compact broadband dual-band circularly polarised slot antenna suitable for the use in the compact universal ultra-high frequency (UHF) radio-frequency identification (RFID) reader devices and Global Positioning System (GPS) applications. The proposed antenna is fed using an open-end coplanar waveguide with an inverted `L' structure. To realise a broadband circular polarisation and good impedance matching, an inverted L-shaped strip line is inserted adequately into a square slot at the right centre of the slot toward the slot centre. The experimental results demonstrate that the proposed antenna exhibits a 10 dB return loss bandwidth of 552 MHz (716-1268 MHz) and 3-dB axial ratio (AR) bandwidth of 564 MHz (824-1388 MHz). Additionally, the antenna gains are 3.8 and 4.29 dBi throughout UHF RFID band and GPS band, respectively. The proposed antenna has a wide AR bandwidth, a compact size, and a simple structure. Furthermore, the proposed antenna is printed on one substrate layer with an overall size of 112 × 112 × 1.6 mm 3 , which makes it more practical for universal UHF RFID handheld readers and GPS applications.

Compact broadband circularly‐polarised antenna with a backed cavity for UHF RFID applications

A compact broadband circularly-polarised (CP) antenna is designed with a novel method for universal ultra-high-frequency (UHF) radio-frequency identification (RFID) readers. It is composed of a compact ring-shaped patch which aims to decrease the size of the antenna. A quadrature 3 dB coupler placed below the ground plane creates 90° phase differences to generate the CP radiation of the antenna. To improve the performance of the proposed antenna and minimise its size, the authors use a coupling feeding method, an FR4 dielectric slab, and a metal cavity. The coupled feeding is implemented to eliminate the mismatching between the long probe and the ring-shaped patch, and to improve the gain over the operating band. The introduction of an FR4 dielectric slab and a cavity can reduce the antenna size and improve the impedance matching and axial-ratio (AR) bandwidth. The antenna with a backed cavity can increase the front-to-back ratio remarkably and improve the CP performance further. The measured results show that the antenna with a low profile (0.45 λ 0 × 0.45 λ 0 × 0.06 λ 0 at 915 MHz) has the impedance bandwidth of 30.2% (730-990 MHz) and 3 dB AR bandwidth of 24.2% (760-970 MHz). Both the impedance and the AR bandwidth cover the worldwide UHF RFID band.

Flexible Radio-Frequency Identification (RFID) Tag Antenna for Sensor Applications.

In this paper, an inkjet-printed flexible Radio-Frequency Identification (RFID) tag antenna is proposed for an ultra-high frequency (UHF) sensor application. The proposed tag antenna facilitates a system-level solution for low-cost and faster mass production of RFID passive tag antenna. The tag antenna consists of a modified meander line radiator with a semi-circular shaped feed network. The structure is printed on photo paper using silver nanoparticle conductive ink. The generic design outline, as well as tag antenna performances for several practical application aspects are investigated. The simulated and measured results verify the coverage of universal UHF RFID band with an omnidirectional radiation pattern and a long-read range of 15 ft. In addition, the read range for different bending angles and lifetimes of the tag antenna are also demonstrated.

A miniaturized ultra‐high frequency microstrip traveling wave antenna Array for cm‐level two‐dimensional identification and position detection systems

AbstractIn this article, a miniaturized ultra‐high frequency (UHF) microstrip traveling wave antenna (TWA) array for cm‐level 2D identification (ID) and position detection systems is proposed. The proposed miniaturized TWA array with nine reading zones for ID and position detection systems has been reduced in size by utilizing LC‐baluns and a microstrip TWA array. It covers the authorized universal UHF radio frequency ID band (840‐960 MHz), has low insertion loss (0.8 dB), and high isolations between TWAs are ≤30 dB. The sensing precision of the proposed TWA array is approximately 1.5 cm and its physical size is 95 × 95 mm2 (~1/4 λ0 at 915 MHz).

Wideband high gain circularly polarized UHF RFID reader microstrip antenna and array

This paper presents a wideband and high gain circularly polarized ultra-high- frequency (UHF) radio frequency identification (RFID) reader microstrip antenna and array. Such antenna unit is composed of one main radiation patch and one parasitic radiation patch with air as the dielectric spacer. Two feeding lines connect to the main radiation patch with 90deg phase difference. Numerical optimizations and experimental demonstrations are performed to investigate the performances of the proposed antenna unit and good agreements are obtained. This antenna unit can cover the whole UHF band (860–960MHz) with gain of 9.7dBi. Then two antenna arrays of 1×4 and 2×2 based on previously demonstrated antenna unit are numerically investigated. The array performances, including the gain, beam scanning and low side-lobe are discussed. The obtained results in this paper indicate that the proposed antenna and array are suitable for the universal UHF RFID applications.

CPW-Fed Wideband Circular Polarized Antenna for UHF RFID Applications

We propose a wide bandwidth antenna with a circular polarization for universal Ultra High Frequency (UHF) radio-frequency identification (RFID) reader applications. To achieve a wide 3 dB axial ratio (AR) bandwidth, three T-shaped microstrip lines are inserted into the ground plane. The measured impedance bandwidth of the proposed antenna is 480 MHz and extends from 660 to 1080 MHz, and the 3 dB AR bandwidth is 350 MHz and extends from 800 to 1155 MHz. The radiation pattern is a bidirectional pattern with a maximum antenna gain of 3.67 dBi. The overall size of the proposed antenna is 114 × 114 × 0.8 mm3.

Single-fed broadband circularly polarized unidirectional antenna using folded plate with parasitic patch for universal UHF RFID readers

This research proposes a simple economical broadband circularly polarized antenna for universal ultra-high frequency (UHF) RF identification (RFID) readers. The antenna utilizes a folded plate, a two-corner truncated parasitic patch, and a ground plane. The folded plate, which is fabricated from one single plate, consists of a two-corner truncated main patch, a wall patch, and a feed line, where the main patch is perpendicular to the wall patch, which is in turn perpendicular to the feed line. The folded plate enables currents to flow with a phase difference. The simulation results achieved an |S11| < −15 dB of 805–966 MHz (18% bandwidth), a 3-dB axial ratio (AR) bandwidth of 834–962 MHz (14% AR bandwidth), and a gain higher than 8.6 dBic. The measured results obtained an |S11| < −15 dB of 806–970 MHz (18%), a 3-dB AR bandwidth of 816–963 MHz (16%), and a gain greater than 7.8 dBic. The proposed antenna is applicable for universal UHF RFID readers as it covers the entire operating UHF RFID frequency range of 840–960 MHz. The parametric study and evolution of the proposed antenna are detailed in this research paper as well. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:575–587, 2016.

Wideband Compact CPW-Fed Circularly Polarized Antenna for Universal UHF RFID Reader

A compact circularly polarized slot antenna is proposed in this communication, which has a much wider operation bandwidth compared to the antennas with similar sizes. This antenna is designed for universal ultrahigh frequency (UHF) radio-frequency identification (RFID) reader applications. The antenna is coplanar waveguide (CPW) fed by an L-shaped feeding line. To achieve good impedance matching and broadband CP operation, two L-shaped strip lines are inserted into the circular slot in the ground plane. The measured 10-dB return loss bandwidth is 380 MHz (618-998 MHz, 47.0% centered at 808 MHz). The measured 3-dB axial ratio bandwidth is about 332 MHz (791-1123 MHz, 34.7% centered at 957 MHz). The overall size of the antenna is 120 × 120 × 0.8 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> .

Compact broadband circularly polarised slot antenna for universal UHF RFID readers

A compact broadband circularly polarised slot antenna is designed for universal ultra-high-frequency (UHF) radio-frequency identification (RFID) readers. The antenna consists of an L-shaped metal strip and a square-slot-loaded ground plane with four tuning stubs. The total size is 100 × 100 × 1.6 mm3. The measured –10 dB impedance bandwidth is 40.7% (772–1166 MHz) and the measured 3 dB axial ratio (AR) bandwidth is 13.9% (840–965 MHz). Both the impedance and the AR bandwidth cover the worldwide UHF RFID band.

Design of a Wideband Inductively Coupled Loop Feed Patch Antenna for UHF RFID Tag

A planar wideband patch antenna for ultra-high frequency (UHF) radio frequ ency identification (RFID) tag for metallic applications is presented in this research work. Three different shape patches ar e inductively coupled to a triangle loop to form wi de impedance bandwidth for uni- versal application UHF (860 – 960 MHz) RFID. The struc- ture of the proposed antenna exhibits planar profile to provide ease of fabrication for cost reduction well suited for mass production. The simulation of the antenna was carried out using Finite Elemen t Method (FEM) based software, Ansoft HFSS v13. The simulated and measured impedance bandwidth of 113 MHz and 117 MHz (Return Loss ≥ 6 dB) were achieved to cover the entire UHF RFID operating frequency band worldwide. The simulated and measured radiation patterns at the operating frequency of 915 MHz are in good agreement. Moreover the simulated maximum antenna gain at th e bore sight direction in free space and when mounted on 200 × 200 mm 2 metal plate are -5.5 dBi and -9 dBi res pectively which is enough to provide reasonable read range over the entire UHF RFID system operating band.

Low-Cost Compact Circularly Polarized Directional Antenna for Universal UHF RFID Handheld Reader Applications

A low-cost compact circularly polarized (CP) directional antenna is proposed for universal ultra-high frequency (UHF) RF identification (RFID) handheld reader applications. The antenna consists of four sequentially rotated inverted-F antennas (IFAs) fed by a compact four-feed network with closed-form design formulas. A prototype is implemented by FR-4 substrates and a thick air layer for the reduction of cost. For return loss (RL) $ > 13~\hbox{dB}$ , 3-dB gain variation, and axial ratio (AR) $ , the prototype achieves the measured bandwidth of 14.9% and exhibits stable symmetrical directional radiation patterns with wide half-power beamwidth. Compared with the reported UHF RFID directional reader antennas, the proposed structure not only exhibits the largest CP bandwidth for easily covering the entire UHF RFID band but also achieves compact size of $95 \times 100 \times 13.6~\hbox{mm}^3$ .

A 1 &lt;formula formulatype="inline"&gt;&lt;tex Notation="TeX"&gt;$\times$&lt;/tex&gt; &lt;/formula&gt; 2 Dual-Band Antenna Array for Radio-Frequency Identification (RFID) Handheld Reader Applications

In this paper, an aperture-coupled dual-band antenna array for ultra-high-frequency (UHF) and microwave band radio-frequency identification (RFID) handheld reader application is presented. The proposed two-element antenna array is composed of a feeding network, a ground plane with coupling apertures, patch radiators, and parasitic elements serving as directors. The spacing between the radiators is optimized to achieve the desired radiation patterns. The experimental results demonstrate that the proposed antenna features good impedance bandwidth, moderate gain, and good radiation efficiency from 840 to 960 MHz (covering a universal UHF band) and 2.38-2.48 GHz (microwave band). The antenna is well suited for applications in RFID handheld readers.

A Koch-Shaped Log-Periodic Dipole Array (LPDA) Antenna for Universal Ultra-High-Frequency (UHF) Radio Frequency Identification (RFID) Handheld Reader

In this communication, we propose a printed log-periodic dipole array (LPDA) antenna covering the universal ultra-high-frequency (UHF) radio frequency identification (RFID) band of operation. Koch-shaped dipoles together with closely-coupled parasitic elements as directors were utilized for compactness in size and improvement in front-to-back ratio (F/B ratio). The experimental results demonstrate that the proposed antenna features good impedance match, moderate gain, better than 80% total radiation efficiency and excellent front-to-back ratio over the universal UHF RFID band from 840 MHz to 960 MHz. The antenna is well suitable for applications in RFID handheld readers.

Design and Development of a Compact Wideband C-Shaped Patch Antenna for UHF RFID Tag

A compact low profile patch antenna for Ultra-High Frequency (UHF) Radio Frequency Identification (RFID) tag for metallic applications is presented in this research study. By employing two gap-coupled C-shaped patches, wide half-power impedance bandwidth (RL ≥3 dB) of 152 MHz is achieved for universal application UHF (860-960 MHz) RFID. Moreover, the proposed patch antenna exhibits planar profile which eliminates the need for cross and multi-layered construction thus resulting in ease of fabrication and reduced cost. The proposed antenna design is simulated using Finite Element Method based software. Reported simulations results demonstrate satisfactory performance when the antenna is mounted on various sizes of metal plate.

Directly-fed single-layer wideband RFID reader antenna

A wideband circularly-polarised (CP) antenna with a simple structure is proposed for universal ultra-high frequency (UHF) radio-frequency identification (RFID) reader applications. The antenna is composed of two patches, an L-shaped ground and an SMA connector. The main patch which is truncated to generate CP radiation is fed directly by the SMA connector oriented in the same plane via the vertical part of the L-shaped ground. The parasitic patch used to enhance the bandwidth is placed at the same layer of the main patch. These two schemes realised a directly-fed single-layer structure. The 3 dB axial ratio bandwidth and impedance matching bandwidth for 14 dB return loss overlap within the universal UHF RFID band (840–960 MHz), while high gain with an average level of 7.3 dBi is achieved. Simulation and measurements are in good agreement.

Single-Fed Broadband Circularly Polarized Stacked Patch Antenna With Horizontally Meandered Strip for Universal UHF RFID Applications

In this paper, a horizontally meandered strip (HMS) feed technique is proposed to achieve good impedance matching and symmetrical broadside radiation patterns for a single-fed broadband circularly polarized stacked patch antenna, which is suitable for universal ultrahigh frequency (UHF) RF identification (RFID) applications. The antenna is composed of two corner truncated patches and an HMS, all of which are printed on the upper side of the FR4 substrates. One end of the HMS is connected to the main patch by a probe, while the other end is connected to an SMA connector. Simulation results are compared with the measurements, and a good agreement is obtained. The measurements show that the antenna has an impedance bandwidth (VSWR <; 1.5) of about 25.8% (758-983 MHz), a 3-dB axial ratio (AR) bandwidth of about 13.5% (838-959 MHz), and a gain level of about 8.6 dBic or larger within the 3-dB AR bandwidth. Therefore, the proposed antenna can be a good candidate for universal UHF RFID readers operating at the UHF band of 840-955 MHz. In addition, a parametric study and a design guideline of the proposed antenna are presented to provide the engineers with information for designing, modifying, and optimizing such an antenna. At last, the proposed antenna is validated in RFID system applications.