Study of miniaturized E‐patch antenna loaded with novel E‐shape SRR metamaterial for RFID applications

A new design of compact micro strip antenna, based on a newly structure "E"SRR of metamaterial is proposed and designed using CST Microwave Studio. It has been found that the characteristics of new micro strip antenna with novel designed metamaterials placed in the same plane as the radiating element are comparable to the conventional patch antennas, whereas its gain, directivity, and radiating efficiency are remarkably improved. For the design and fabricated antenna, it shows that with the addition of split ring resonator, the frequency has been shifted from 2.38 GHz to 2.4 GHz. The return loss of this antenna increased from ?60 dB to ?70 dB. The realized gain increased from 7.1 dbi for the antenna alone to 7.31 dbi for the meta‐material antenna. Prototype for all antennas are fabricated and measured. Good agreement between the measured and simulated results is achieved.     

Path loss compensated millimeter wave antenna module integrated with 3D‐printed radome

Millimeter wave antennas designed at 28 GHz is essential for future 5G base stations or access points and mobile terminals. In this paper, a compact pattern diversity module for millimeter wave 5G base stations is proposed by using 3D‐printing for radome design. In order to achieve path loss compensation in an indoor base station context, the gains of the antennas radiating at ±45° must be 3 dB higher than the antenna radiating in the boresight axis. First, an inset fed patch antenna integrated with a low‐cost industry standard 3D‐printed superstrate with Polylactic acid (PLA) is investigated to study its radiation characteristics. The radome is designed in such a way for optimal gain enhancement with minimal physical footprint. The height of the 2 mm thick superstrate is optimized for a boresight gain of 8 dBi. Second, the 3D‐printed superstrate is optimized for a boresight gain of 11 dBi, which satisfies the criterion of path loss compensation, in this case the antenna achieves an aperture efficiency of close to 72% at 28 GHz. A compact pattern diversity module with customized 3D‐printed radome is also presented to achieve path loss compensation and wide angular coverage of ±70° with associated isolation of less than 35 dB across the ports and the band. Detailed simulation and measurement results are presented.     

Direct and electromagnetically coupled compact microstrip antenna design with modified fractal DGS

This article proposes ultra‐miniature microstrip patches with direct and electromagnetically coupled feeding mechanism for wireless communications at 10 GHz. Antenna size reduction is achieved here by loading a modified Minkowski fractal (type‐2) defected ground structure (MFDGS‐II) exactly beneath the radiating patch. The proposed method involves the selection of best DGS configuration through sensitivity analysis of the antenna structure. From different applications point of view, three different designs: a single layer direct fed patch and two electromagnetically coupled fed multi‐layered microstrip patch antennas are proposed here and designed with MFDGS‐II. The resonant frequencies of the antenna designs are reduced in a significant manner incorporating MFDGS‐II without any change in the physical size of the antenna. The prototypes of the proposed antennas are fabricated, and the performance parameters are measured. Compared with other existing structures, with a lower patch size of 0.20 λ₀ × 0.15 λ₀, the proposed single layered antenna with microstrip feed achieves a patch size reduction up to 67% and an overall volumetric reduction of 84%, respectively. Similarly, the proposed multi‐layered patch with proximity feed exhibits a maximum impedance bandwidth of 600 MHz and the aperture coupled fed patch has a realized gain of 6.2 dBi with radiation efficiency of 91% centered at 10 GHz. All three proposed compact antenna structures are best in three different aspects and have the potential to meet the practical requirements for X‐band portable wireless applications.     

A compact and wideband array antenna with efficient hybrid feed network

This study presents a high‐efficient, compact, and broadband microstrip patch antennas (MPAs) based on substrate‐integrated waveguide (SIW) for X‐band applications. The proposed array consists of three stacked layers from top to bottom, including one layer as the antenna layer and two SIW layers as a feeding network. The performance was focused on improving the impedance bandwidth and radiation efficiency by mitigating the loss from the feed network while also maintaining the compact design. To this end, the SIW feeding network was designed to feed the MPA to save the physical aperture size which resulted in a more compact and efficient radiating structure. The overall size of the proposed array is compact and extra surface area around the radiation aperture has not been occupied. The measured ?10 dB impedance bandwidth span is from 8.9 to 10.9 GHz (20.2%). The maximum measured gain at 10.6 GHz is 10.6 dBi. The results show that the simulated radiation efficiency and the measured aperture efficiency are more than 75% and 50%, respectively. The fabricated array exhibits great advantages such as wide operating bandwidth, lightweight, low‐cost, high aperture efficiency, high radiation efficiency, and compactness which make it a good candidate for X‐band applications.     

Isolation enhancement between tightly spaced compact unidirectional patch‐antennas on multilayer EBG surfaces

In this article, ultracompact unidirectional patch antennas are used in different two‐antenna systems for biomedical applications at 5.2 GHz. Multilayer mushroom type electromagnetic bandgap (EBG) structures are designed as slow‐wave medium to reduce the size of the individual patch antennas to 0.1λ₀ by 0.18λ₀. Various techniques are investigated herein to improve antenna isolation for an enhanced Multiple‐Input Multiple‐Output (MIMO) performance. First, the coupling between 0.3λ₀‐spaced antennas is verified to occur dominantly through radiation and near‐field coupling between the patches rather than through substrate‐bound modes. Second, various configurations are proposed to suppress antenna coupling. These approaches include reorientation of the antennas and employment of parasitic radiators between the patches. A novel design is presented in which a unidirectional parasitic slot radiator on an EBG reflector is inserted between the antennas to decouple them. Measurement results confirm efficacy of these approaches in mitigating antenna coupling by more than 11 dB in the operating bandwidth of the antennas. The compact patch antennas maintain efficiency values of higher than 70%. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:30–38, 2015.     

A reconfigurable multiband rhombic shaped microstrip antenna for wireless smart applications

This article proposes a reconfigurable multiband rhombic shaped microstrip antenna (RMRS‐MSA) up to 20 GHz based on wireless smart applications. In this article radio frequency (RF) PIN diodes are loaded with microstrip feed line on radiating patch for frequency switching. It has a rhombic shaped copper loaded radiating patch. This radiating patch has two more connected rhombic patches inside with a 1 mm gap named as radiating patch 1 and radiating patch 2. These rhombic shaped radiating patches are enclosed with a square parasitic patch for achieving directional radiation pattern. A prototype of reconfigurable multiband rhombic shaped reconfigurable MSA is fabricated using a 30 × 30 mm² on FR‐4 substrate with a dielectric thickness of 1.6 mm. The proposed RMRS‐MSA is designed, fabricated, and experimentally validated. The experimental report at center frequency 5.21, 9.41, 10.46, 12.69, 14.39, and 17.09 GHz have reflection coefficients of ?16.89, ?25.54, ?24.86, ?28.62, ?26.80 and ?43.02 dB, respectively, when all diodes are OFF. Similarly, when all diodes are ON, at center frequency 14.57 and 15.18 GHz have reflection coefficients of ?26.15 and ?28.99 dB, respectively. The measured and simulated results agree well. The proposed antenna is more suitable for C, X, and Ku band‐based applications.     

Miniaturization and dual‐banding of an elevated slotted patch antenna using the novel dual‐reverse‐arrow fractal

A novel fractal geometry called dual‐reverse‐arrow fractal (DRAF) is introduced and compared with various versions of Koch fractals for application to triangular patch antennas. It is shown that DRAF results in the reduction of antenna size and tends to maintain its bandwidth. The presented DRAF is applied for the reduction of size of an elevated triangular patch antenna for the dual band operation in WLAN. This DRAF antenna has achieved 40% size reduction compared to a simple triangular patch antenna. For the provision of required bandwidth in the second frequency band (4.9‐5.9 GHz), a stepped U‐shaped slot is cut in the triangular patch. This antenna is more compact than similar antennas reported in the literature but maintains its fractional bandwidth (%25). The optimized design of the proposed DRAF antenna with air gap and slot is fabricated and tested, which verifies its expected specifications.     

RFID tag antenna for ultra and super high frequency band applications

A novel dual‐band antenna for radio frequency identification tag is proposed for ultra high frequency (UHF: 915 MHz) and super high frequency (SHF: 2450 MHz) bands. The proposed tag antenna is a single sided dual‐antenna structure, designed on the grounded (metallic) dielectric substrate. The proposed tag antenna can be used on any kind of surfaces including metals without severe performance degradation due to its metallic ground plane. At UHF band, proposed tag antenna works as dual‐antenna structure. In the dual‐antenna structure, one antenna works for receiving and another for backscattering. Due to separate backscatterer, the maximum differential radar cross section improved and results in the enhancement of the maximum read range. Whereas at SHF band, proposed antenna works as conventional single antenna structure and during operations it switches between receiving and backscattering modes. The proposed antenna consists of a meandered line antenna and a rectangular patch antenna loaded with an F‐shaped and an inverted L‐shaped slots. The S‐parameters are measured by means of differential probe technique. Simulated and measured results are observed in good agreement. The read range is observed about 5 and 6 m at 915 and 2450 MHz, respectively. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:640–650, 2016.     

Low profile coupling feed circularly polarized antennas for WLAN applications

This article presents two designs of circularly polarized antenna with simple circular‐shaped radiator and circular slotted ground plane. An arc‐shaped microstrip line coupling feed mechanism is used to excite the circular radiating patch. The 3‐dB axial ratio bandwidth of the proposed antenna‐1 and proposed antenna‐2 are 3.33% and 18%, respectively. The proposed design has several advantages such as easy matching, fabrication simplicity, compact size, and wide axial ratio bandwidth. Both the antennas have been designed on FR‐4 substrate with dielectric constant 4.4 and thickness 1.59 mm. Simulated and measured results are presented to validate the working of the proposed antennas.     

A high gain wideband circularly polarized antenna with asymmetric metasurface

An asymmetric‐metasurface based wideband circularly polarized (CP) microstrip antenna using a coaxial probe is proposed for L‐band applications. The antenna involves a stacked asymmetric‐metasurface, a radiating rectangular‐patch and a coaxial feed. An asymmetric‐metasurface is designed using rectangular unit cells and smaller size unit cells along one of the diagonal lines. The asymmetric‐metasurface is placed above a radiating rectangular‐patch with support of foam layer to achieve a wideband CP radiation. The measured performance of the prototype antenna achieves an impedance bandwidth (?10 dB return loss bandwidth) of 15.7% (1.58‐1.85 GHz) with CP bandwidth (3‐dB axial ratio) of 13% (1.58‐1.80 GHz) and gain of ≥9 dBic.     

Design of multi band triangular microstrip patch antenna with triangular split ring resonator for S band,C band and X band applications

With the rapid advancement in multi-functional communication devices, devices capable of operating for more than one frequency bands emerged. Such applications demand for multiband antennas. Wide band antennas are capable of resonating over larger frequency bands, but it limits the impedance bandwidth and gain. So, the solution of this could be compact multi band antennas. A quad band Triangular Microstrip antenna designed for IEEE 802.16e Wi-MAX, IEEE 802.11a WLAN, C band downlink communication and x band radar applications is suggested in this work. The proposed antenna has triangular patch with triangular split ring resonator. The conservativeness and data transfer capacity are the preferred possessions of the suggested antenna. The proposed antenna yields better return and gain by resonating in 3.5 GHz, 4.1 GHz, 5.6 GHz and 9.7 GHz.     

A dual band dual antenna with read range enhancement for UHF RFID tags

This article presents a novel dual antenna structure for dual ultra high frequency bands (f₁ = 866 MHz and f₂ = 915 MHz) for radio frequency identification tags. The proposed structure consists of two dual band antennas, one acting as a receiving antenna and the other as a backscattering antenna at both the frequency bands. The receiving antenna is designed to have input impedance complex conjugate to the impedance of tag IC in order to maximize power transfer between the antenna and the microchip. The backscattered antenna is designed to have real‐valued input impedance at both the operating frequency bands to obtain maximum differential radar cross section leading to read range enhancement. The dual band receiving antenna is designed by embedding a pair of thin slits at a radiating edge of inset fed microstrip antenna. The backscattering antenna is comprised of two elements, one is a comb‐shaped open ring element, and the other is a meander line structure which is within the open ring element. Compared to conventional antennas, the proposed dual antenna structure provides a read range enhancement due to improved maximum differential RCS. The proposed dual antenna produced 4.3 m and 6.8 m read range at 866 MHz and 915 MHz, respectively.     

A compact implantable RFID tag antenna dedicated to wireless health care

Implantable tag antennas are an integral component of contemporary pervasive patient monitoring setups envisioned to reduce the medical errors and improve the quality of health care facilities. These tags, embedded into the human body, transmit critical patient information to the external equipment via a wireless communication link. This research article presents an implantable compact folded dipole antenna of size 10 mm × 15 mm × 2 mm, designed to operate in the industrial‐scientific‐medical band (2.4‐2.48GHz). A three‐layered phantom representing the human arm is used to evaluate the subcutaneous antenna performance. The tag antenna embedded in the middle of the fat layer offers a maximum gain of ?16.3 dBi. The tag antenna performance as a function of implant position and phantom dimensions is analyzed. Link budget calculations show that with the achieved antenna gain the link power exceeds the required power by 38.37 dBm, and hence wireless communication is viable.     

Novel single‐fed broadband circularly polarized antenna for GNSS applications

This letter presents the design of a broadband microstrip CP antenna using single‐fed technique. The feeding network is integrated within the coupling feed patch to simplify the structure. The proposed antenna is designed for Global Navigation satellite System (GNSS) operating at 1575.42 ± 10.23 MHz (GPS: L1 band), 1559～1592 MHz (Galileo: E2‐L1‐E1 band), 1602 ± 5.625 MHz (GLONASS: L1 band) and 1559.052～1591.788 MHz & 1610～1626.5 MHz (BeiDou Navigation Satellite System B1 and L band). Another advantage of this antenna is the much wider bandwidth in both VSWR and 3 dB axial‐ratio compared with traditional single‐fed CP antennas. Details of design, simulated and experimental results of this CP antenna are presented and discussed. The measured results confirm the validity of this design which meet the requirement of GNSS applications.     

Performance enhancement of nested hexagonal ring‐shaped compact multiband integrated wideband fractal antennas for wireless applications

In this paper, nested hexagonal ring‐shaped fractal antennas are designed and investigated which are different from each other in patch orientation. Initially, the multiband integrated wideband hexagonal nested ring antenna is designed (antenna‐I). To improve the multiband/wideband behavior, the patch orientation of antenna‐I is changed to ?60°/60° (antenna‐II), ?120°/120° (antenna‐III), and ?180°/180° (antenna‐IV). Antennas are designed on low cost FR‐4 glass epoxy substrate with relative permittivity of 4.4 and overall dimension 30 × 30 × 1.6 mm³. Comparison among antennas have been made and found that the antennas with negative orientation exhibit better results in terms of bandwidth, impedance matching, number of frequency bands, and gain. Designed antennas have been compared with each other and found that antennas‐II and III are better in performance as compared to antennas‐I and IV. Antenna‐II exhibits wider bandwidth of 1.26 (2.52‐3.78 GHz), 2.75 (4.03‐6.78 GHz), and 6.1 GHz (7.82‐13.92 GHz) with maximum gain of 7.14 dB. Similarly; antenna‐III exhibits the bandwidth of 340 MHz (1.92‐2.26 GHz), 820 MHz (3.04‐3.86 GHz), 4230 MHz (5.38‐9.61 GHz), and 3040 MHz (10.41‐13.45 GHz) with a maximum gain of 6.19 dB. Prototype of the designed antennas with satisfactory orientations are fabricated and tested for the validation of results. Simulated and measured results are also juxtaposed and observed in good agreement with each other. Antennas exhibit bidirectional and omnidirectional pattern in E‐plane and H‐plane, respectively, also the radiation efficiency of antennas are in acceptable range from 75% to 95%. Due to the wider bandwidth of designed antennas, they can be used for different wireless standards such as Advance Wireless Services AWS‐1, AWS‐2, AWS‐3, Wi‐MAX, WLAN, X‐band satellite communication, point‐to‐point wireless applications, ITU band, military satellite communication, television broadcasting, and military land and airborne systems.     

Quad notch UWB antenna using combination of slots and split‐ring resonator

A novel coplanar waveguide fed UWB antenna with quad notch band characteristics has been proposed in this work. The antenna layout is designed based on a combination of well‐known geometrical shapes: a half ellipse patch, rectangle, and triangle. The shape of the ground plane is partially tapered rectangular. The overall dimension of the antenna is 41.5 × 32 mm. The antenna uses three U‐shaped slots at the top surface to create three notched band characteristics. A split‐ring resonator is then introduced at the bottom surface of the antenna. With the integration of split‐ring resonator at the bottom surface, an additional notch band at 7.25 to 7.75 (6.7%) GHz is created in the antenna. The designed antenna has an operating impedance bandwidth (VSWR ≤2) ranges from 3.03 to 12.34 GHz except in quad frequency stop bands of 3.3 to 3.7 (11.4%), 5.15 to 5.35 (3.8%), 5.725 to 5.825 (1.7%), and 7.25 to 7.75 (6.7%) GHz. The proposed antennas are successfully designed, prototyped, and measured. The simulated and measured results are extensively studied and discussed. Correlation between the time‐domain transmitting antenna input signal and the received antenna output signal is calculated in order to ensure that the proposed antenna can be used in pulse‐communication systems. This antenna finds applications in medical imaging, military radar systems, and other common UWB applications.     

Compact UWB flexible elliptical CPW‐fed antenna with triple notch bands for wireless communications

A coplanar waveguide (CPW)‐fed flexible elliptical antenna with triple band notched characteristics is presented in this article. The designed antenna consists of an elliptical patch and slots incorporated CPW feed line to cover the bandwidth requirements for ultra‐wideband (UWB) applications. The designed UWB antenna has a fractional bandwidth of about 166.19% (1.20‐13 GHz) with a center frequency of 7.1 GHz in simulation and about 170.10% (1.05‐13 GHz) with a center frequency of 7.025 GHz in measurement. The overall dimension of the proposed flexible antenna is 45 × 35 × 0.6 mm³. The triple notched bands are realized by designing with circular shaped split‐ring‐resonators (SRRs) and defected ground structure (DGS). According to the measurement, first notched band (2.0? 2.70 GHz) is generated for rejecting 2.4 GHz WLAN by introducing a single circular ST‐SRR on the radiating patch. The second notch (3.45‐3.80 GHz) is obtained by embedding another circular ST‐SRR on the patch to mitigate the interference of 3.5 GHz Wi‐MAX system. Finally, due to presence of DGS, third notch (5.15‐6.20 GHz) is produced which suppresses the interference from 5.5 GHz Wi‐MAX and 5.2/5.8 GHz WLAN systems. The proposed antenna offers excellent performance in different flexible conditions that confirm its applicability on curved surfaces for UWB systems.     

Fork‐shaped patch printed ultra‐wideband slot antenna with dual band‐notched characteristics using metamaterial unit cells

In this article, a miniaturized fork‐shaped patch ultra‐wideband (UWB) planar wide‐slot antenna with dual band‐notched characteristics is proposed. With fork‐shaped patch, ultra‐wideband impedance matching from 3.1 to 13.2 GHz is easily achieved. Then, two novel and simple methods are applied to solve the difficulty for UWB slot antennas with fork‐shaped patch to realize band‐notched characteristics. By etching one pair of I‐shaped resonators on both branches of the fork‐shaped structure and adding a rectangular single split‐ring resonator in the rectangular openings of fork‐shaped patch, the wireless local area network (WLAN) band from 5.5 to 6.1 GHz and the International Telecommunication Union (ITU) 8 GHz band from 7.9 to 8.7 GHz are rejected, respectively. The coplanar waveguide‐fed UWB antenna is successfully designed, fabricated, and measured. The measured and simulated results show a good agreement. The antenna provides nearly stable radiation patterns, high gains and high radiation efficiency.     

Design of a compact protrudent‐shaped ultra‐wideband multiple‐input‐multiple‐output/diversity antenna with band‐rejection capability

In this endeavor, a new multiple‐input‐multiple‐output antenna with a sharp rejection at wireless local area network (WLAN) band is designed and practically examined for portable wireless ultra‐wideband applications. The intended diversity antenna possess a small size of 15 mm × 26 mm and two inverted L‐strip are loaded over the conventional rectangular patch antenna to form protrudent‐shaped radiator that acts as a radiating element. The sharp band‐rejection capability at WLAN is established by incising the L‐shaped slits at the decoupling structure. More than ?21 dB isolation is accomplished for the complete working band (ie, 2.87 ‐17 GHz). Degradation in the antenna efficiency at the center frequency of band rejection corroborates the good interference rejection capability. The working capabilities of the intended antenna are tested by using the isolation between the ports, total efficiency, gain, envelope correlation coefficient, radiation pattern, mean effective gain, and total active reflection coefficient.     

Design of a compact size tag antenna based on split ring resonator for UHF RFID application

In this article, a new design of miniaturized split‐ring resonator antenna using a meander line technique with a simple impedance matching method applicable to UHF‐RFID tags is presented. The new approach is based on the integration of a meander line into the radiating element of SRR to reduce the electrical tag size and a theoretical demonstration to calculate the conjugate impedance matching and directly attach the antenna with the chip. The new SRR antenna, which is printed on the flexible substrate Arlon CuClad 250LX, is designed using Alien Higgs 3 RFID ASIC whose input impedance is 25‐j190. The prototype antenna has a low‐cost compact size (18.28 mm × 18.28 mm) with a read range higher than 4 m within the RFID UHF band and with a roughly 4.2‐m peak range at 915 MHz. As a proof of behavior, a tag prototype is fabricated and measured to operate at a UHF RFID band. Based on some works' results, an optimized design is obtained with a 48% size reduction compared with the classic split ring resonator antenna and with a good impedance matching the antenna with RFID ASIC without the need for any external matching network.