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An extremely low-profile/compact MIMO system is proposed by utilizing the dual antenna for 5G sub-6 GHz and mm-wave application. The antennas are integrated on a centrally located square-shaped slot-loaded octagon-shaped substrate board area of 3706.69 mm2. The identical dual antenna elements with the same orientation are orthogonally placed on an octagon-shaped substrate from the outer side, creating an 8-element MIMO antenna for sub-6 GHz application. From the inner side of the same substrate, a $1\mathbf {\times }4$ array-based antenna is orthogonally placed in front of the remaining side of the octagon, forming a 4-element MIMO antenna for mm-wave application. The edge-to-edge separation between element-1 and -9 is almost close to $\lambda _{0}$ /64 ($\lambda _{0}$ at 4.0 GHz). The stubs are connected to shared ground plane to reduce the coupling between closely placed antenna elements. The MIMO system provides dual −6 dB impedance bandwidth of ($S_{ij}{}_{\,\,} \mathbf {\mathrm {\in }}\,\,{i} = {j}$ , 1 to 8) 4.0–5.6 GHz and ($S_{ij}{}_{\,\,} \mathbf {\mathrm {\in }}\,\,{i} = {j}$ , 9 to 12) 24.25–29.5 GHz, can cover the 5G n79//n257/n258 bands. It has a minimum isolation ($S_{ij~}\mathbf {\mathrm {\in }}~{i} \mathbf {\mathrm {\ne }} {j}$) value of 12 dB and 22 dB, respectively. Also, the peak gain and total efficiency values for element-1 and -9 are 5.4 dBi and 8 dBi, and 56.5–77.4% and 70.3–96.2%, respectively. The measured and simulated results are found in close agreement those confirming that the proposed MIMO system may be a suitable candidate for 5G-smartphones. Due to 0.508 mm low-profile, antenna is integrated within the back cover of smartphones, thereby inside device volume will reduce. [ABSTRACT FROM AUTHOR]

In this brief, a low-profile wideband quad-element MIMO antenna with high isolation is designed, which is utilized to propose a 20-elements MIMO system. Each element of the MIMO antenna covers a wideband occupying a small area of $15\times 15$ mm2. The orthogonal symmetric arrangement of a single antenna forms an extremely compact quad-element MIMO antenna having shared ground, and its occupied volume is $0.84\lambda _{\mathrm{ g}} \times 0.84\lambda _{\mathrm{ g}} \times 0.019 \lambda _{\mathrm{ g}}$ ($\lambda _{\mathrm{ g}}$ at 3.95 GHz) with a minimum ($0.155 \lambda _{\mathrm{ g}}$) edge to edge distance between elements. The proposed antenna has a −10 dB ($S _{ij} \in i=j$) impedance bandwidth of 77.52% (3.95–8.95 GHz) and a minimum isolation ($S _{ij} \in i \ne j$) value of 17 dB. The measured and simulated results are found in good agreement that confirms the proposed antenna is appropriate for extending a higher-order MIMO system. Further, a low-profile quad-element MIMO antennas are arranged orthogonally at the four-corners and a quad-element MIMO antenna at the center of form a 20-elements planar MIMO antenna. It can be utilized as a localization system where different user’s devices are connected to the primary host. [ABSTRACT FROM AUTHOR]

In this article, a metamaterial absorber structure is analyzed using the transmission line method (TLM) considering the normal incidence of the wave. The unit cell of the presented absorber structure is a composite geometry providing dual‐band absorption. Peak absorptivities of 95.02% and 99.84% are obtained at 4.215 GHz and 10.95 GHz, respectively. The experimentally validated simulated reflection response is used as a reference to validate the analytical response of the absorber structure. To obtain the equivalent circuit model, the frequency selective surface (FSS) forming the absorber top layer is considered as a combination of two simpler FSS. The individual absorbers formed by two such FSS are correctly modeled using TLM. The obtained equivalent circuits are then combined suitably by incorporating the involved coupling capacitances into the calculation. The analytical and simulated response of the presented absorber structure is found in good agreement. The presented decomposition approach for the development of a circuit model of the composite FSS is promising and it would pave the way in obtaining the good physical insight of the multiband metamaterial absorber structures. [ABSTRACT FROM AUTHOR]

A compact two‐element multiple‐input‐multiple‐output (MIMO) antenna system with improved impedance matching and isolation is presented for future sub‐6 GHz 5G applications. The two identical tapered microstrip line fed modified rhombus‐shaped radiating elements are placed in the same orientation at a compact substrate area of 0.24λ0 × 0.42λ0 (where, λ0 at 3.6 GHz) on a shared rectangular ground. A remodeled T‐shaped ground stub is placed between a pair of radiating element to achieve improved impedance bandwidth and isolation. Further, a split U‐shaped stub connected to center of each radiating element to achieve the desired resonant frequency of 3.6 GHz. The proposed antenna covers a −10 dB operating band of 3.34 to 3.87 GHz (530 MHz) with more than 20 dB isolation between a pair of elements. MIMO performances are also analyzed and experimentally validated. The measured performances of a prototype are found in good agreement with simulated performances. Further, the simulation study is carried out to see the effect of housing and extended ground plane on two‐element MIMO antenna for practical application. An idea of realization of 12‐element MIMO is also studied using the proposed two‐element MIMO antenna. [ABSTRACT FROM AUTHOR]

A new compact ultra-wideband (UWB) filtering antenna having good band-edge selectivity and suppressed unwanted harmonics is proposed in this paper. The proposed UWB filtering antenna is obtained by integrating modified elliptic-shaped UWB antenna with super-compact UWB bandpass filter (BPF). Initially, a UWB antenna is designed and investigated through numerical simulation and experimentally. Further, the geometrical parameters of BPF are optimized using numerical simulation software for its integration with the proposed UWB antenna to improve the passband selectivity and unwanted harmonic suppression capability of the proposed UWB filtering antenna. The proposed UWB filtering antenna has simulated −10 dB impedance bandwidth of 7.65 GHz (3.07-10.72 GHz) and unwanted harmonic suppression up to 30 GHz. It has nearly stable omnidirectional radiation patterns over whole UWB frequency band. The proposed filtering antenna was fabricated and experimentally tested. The experimental results for the filtering antenna are nearly in agreement with corresponding simulation results. [ABSTRACT FROM AUTHOR]

A polarization insensitive, wide angle low profile metamaterial absorber with dual-band absorption characteristics in C- and X-frequency bands is presented in this paper. The parametric variation is discussed in details to understand the dependence of absorption frequency and absorption level on the design parameters. The proposed structure supports the realization of near unity absorption at the two absorption frequencies independently by suitably varying the design parameters. The absorption mechanism is explained with the E-field and surface current distribution plots at the peak absorption frequencies. The absorption is due to the simultaneous excitation of electric and magnetic resonance in the structure. Constitutive electromagnetic parameters of the proposed structure are also retrieved and plotted against frequency. A sample of the proposed absorber is fabricated and measured response validates the numerical results. [ABSTRACT FROM AUTHOR]

Abstract: A compact lowpass filter (LPF) with wide stopband which uses four non‐uniform cascaded defected ground structure (DGS) units along with a 50 Ω microstrip line is reported in this article. Each DGS unit, which consists of a combination of three isosceles U‐shaped DGSs is analyzed in terms of an equivalent RLC circuit model. Every DGS of the DGS unit along with microstrip line provides one attenuation pole. It is found through performance comparison of the proposed U‐shaped DGS with dumbbell‐ and fork‐shaped DGSs that the proposed U‐shaped DGS is compact and provides higher quality factor. Further, the modeling of the proposed LPF is carried out using equivalent RLC circuit model. The results obtained through numerical and circuit simulations are compared. The proposed LPF has size of 14.44 mm × 3.4 mm, 3‐dB cut‐off frequency of 14.2 GHz, and greater than 40 dB and 22 dB stopband rejection up to 21.8 GHz and 30 GHz respectively. The proposed LPF is fabricated and experimentally tested. The experimental results are nearly in agreement with corresponding numerical/circuit simulation results. [ABSTRACT FROM AUTHOR]

A super-compact ultra-wideband (UWB) microstrip band-pass filter (BPF) with good selectivity and wide stopband is proposed in this paper. The super-compactness along with wide stopband of the proposed filter is achieved by integrating modified multimode resonator-based UWB BPF and defected ground structure (DGS)-based compact low-pass filter (LPF). The LPF structure is designed using four non-uniform configurations of DGS units along with a 50 Ω microstrip line. Each DGS unit is formed by cascading three isosceles U-shaped DGSs. Further, an equivalent RLC circuit model of the LPF is proposed to validate the numerical simulation and experimental results of LPF. The proposed filter has simulated passband frequency range 3-11 GHz with wide stopband: attenuation better than 40 dB and 25 dB over the frequency ranges 11.7-20.5 GHz and 11.2-30 GHz respectively. The experimental results for the proposed filter are nearly in agreement with corresponding numerical simulation results. [ABSTRACT FROM AUTHOR]

A meandered-dual-antenna structure is proposed for UHF radiofrequency identification (RFID) tag. It is composed of two independent antennas printed on the one side of the substrate board. One of the antennas is exclusively used for receiving and harvesting sufficient energy to the tag chip having the complex conjugate impedance of the receiving antenna. The other is for backscatter to enhance maximum differential radar cross-section with purely real input impedance, to enhancement the read range. The receiving antenna is formed by a rectangular loop and a parasitic meandered line. The rectangular loop is used as a feeding element for the meandered line. The backscattering antenna is made using a meandered dipole along with a thin rectangular strip. The input impedance of the receiving antenna is designed to be conjugate matched to the chip impedance (13.5-j110 Ω), whereas the input impedance of backscattering antenna alternatively switched to open and short circuit for modulating the backscattered field. The input impedance of receiving and backscattering antennas is measured using differential probe technique. The simulated and measured results are found in good agreement. It is also demonstrated that the read range of UHF RFID system increased considerably by using the dual-antenna structure. [ABSTRACT FROM PUBLISHER]

ABSTRACT 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. [ABSTRACT FROM AUTHOR]

ABSTRACT To mitigate the interference with coexisting wireless systems operating over 3.3-3.6 GHz, 5.15-5.825 GHz, and 7.725-8.5 GHz bands, a novel triple band notched coplanar waveguide fed pitcher-shaped planar monopole antenna is presented for ultrawideband applications. Bands notched characteristics are achieved using a novel mushroom type electromagnetic band gap structure like resonator and a split ring slot. A conceptual equivalent RLC (Resistor-Inductor-Capacitor)-resonant circuit is presented for the band notched characteristics . Furthermore, the input impedance and VSWR (voltage standing wave ratio) obtained from the equivalent circuit are validated with simulated and measured results. Performances of the antennas in both, the frequency domain and the time domain are investigated. The simulated and measured results demonstrate that the proposed antennas have wide impedance bandwidth, nearly stable radiation patterns, and suppression of gain and total radiation efficiency at notched bands. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:795-806, 2015. [ABSTRACT FROM AUTHOR]

ABSTRACT A low profile triband compact multiple input multiple output (MIMO) antenna operating at WLAN, WiMAX, and HIPERLAN bands is presented. The proposed MIMO antenna consists of two planar inverted-F antenna elements located at the top two corners of printed circuit board (PCB). Dimensions of each antenna elements are reduced substantially by employing a meandered line and folded patch structure so that it occupies a small volume of 9 × 8.8 × 5.4 mm3. The proposed antenna consists of three arms namely, Main arm, Side arm 1, and Side arm 2. Each individual arm resonates corresponding to the λ/4 electrical length. Characterization of the antenna is carried out in the mobile environment as well as in user proximity. In the presence of mobile environment which includes liquid crystal display (LCD), Battery, RF components, and plastic housing, the isolation as well as reflection coefficient parameters deteriorated. To avoid the aggravation of S-parameters, two nonradiating folded shorting strips are connected between each antenna element and ground plane of PCB. This folded shorting strip not only improves the isolation between ports but also prevent the deterioration of reflection coefficient parameter. The total efficiency, envelope correlation coefficient, and multiplexing efficiency are studied in the user proximity. The optimized structure is fabricated and measured. The measured S-parameters cover WLAN (2.46-2.6 GHz), WiMAX (3.37-3.75 GHz), and HIPERLAN (5.2-5.87 GHz) based on −10 dB reflection coefficient and −24 dB isolation is achieved between antenna ports. Good agreement is obtained between the simulated and measured results. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:510-521, 2015. [ABSTRACT FROM AUTHOR]

ABSTRACT A compact, multiband, shorted monopole antenna is presented for ultraslim mobile handsets. The proposed antenna is formed by a simple structure of three radiating strips of different length namely, λ/4 C-shaped radiating strip, 3λ/8 meandered line radiating strip, and a λ/4 shorting strip. Which results in proposed antenna that covers GSM850/900/1800/1900/UMTS/Wi-Fi/LTE2300/2500/WiMAX bands with respect to −6 dB impedance bandwidth. The measured peak realized gain is observed between 1.2 and 4.2 dBi while simulated total radiation efficiency is between 60 to 93% in the operating bands. The proposed antenna is investigated in free space as well as in actual mobile environment consisting of mobile plastic housing along with large metallic display screen and battery. Specific absorption rate computation is also carried out on human head phantom in vicinity of the proposed antenna and obtained well below the specified limit. The parametric analysis is also carried out to understand the effect of the shape parameters of the antenna. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1459-1466, 2015 [ABSTRACT FROM AUTHOR]

ABSTRACT A compact dual-band multiple-input multiple-output (MIMO) antenna is presented for wireless local area networks (2.45/5.8 GHz) applications in mobile handsets. The proposed MIMO antenna consists of two planar inverted-F antennas loaded with inverted J-shaped slot and inverted L-shaped slot. The defected ground structure of fork shaped slot is proposed between antenna elements to achieve high port-to-port isolation (<−20 dB). The distribution of specific absorption rate (SAR) over 1-g and 10-g tissues in human head are also studied for two different positions of the antenna at 2.45/5.8 GHz frequencies through SAR to PEAK location spacing ratio (SPLSR) according to Federal Communication Commission standard. The values of SPLSR are observed over 1-g of tissues between 0.107 and 0.246 W/kg/cm and 0.304-0.122 W/kg/cm and over 10-g of tissues between 0.242 and 0.124 W/kg/cm and 0.154 and 0.045 W/kg/cm at 2.45 GHz and 5.8 GHz, respectively. The S-parameters, surface current distribution, diversity parameters, and radiation patterns are presented. The fabricated prototype are measured and obtained good agreement with simulated results. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:906-912, 2015 [ABSTRACT FROM AUTHOR]

A planar compact multiband monopole antenna is presented for ultra-slim mobile handset applications. The proposed antenna operates over 0.885 GHz-0.962 GHz and 1.69 GHz-3.8GHz frequency bands with -6 dB impedance bandwidth that covers GSM900, GSM1800, GSM1900, UMTS, IMT2100, WLAN, WiMAX along with most of the higher LTE bands of modern mobile phone applications. The radiation characteristics of the antenna is analyzed in term of radiation patterns, peak realized gain, total radiation efficiency, and surface current distribution. The radiation patterns of the proposed antenna are dipole like which is suitable for mobile applications with 73-93% total radiation efficiency. The proposed antenna is investigated in free space as well as in actual mobile environment consisting of mobile plastic housing along with large metallic display screen and battery. No significant effect on the operating bands of the mobile antenna due to the actual mobile environment on the impedance bandwidth is observed. Specific absorption rate (SAR) computation is carried out on human head phantom. The computed values of SAR lie well below the specified limit over 1 g and 10 g of tissues. The parametric analysis is also carried out to understand the effect of the shape parameters. [ABSTRACT FROM AUTHOR]

In this letter, a low-profile quad-band antenna array for multiple-input-multiple-output (MIMO) application has been presented. The proposed two-antenna array operates at GPS L1/Bluetooth/Wi-Fi/LTE2500/WiMAX/HIPERLAN1 frequency bands. Each antenna element has an area of 25 × 10 mm2 over a small ground plane of the size 100 × 60 mm2. To maintain the small size of the antenna element, folded patch is used. A rectangular slot is etched on the main radiator to utilize the higher-order mode. A quarter-wavelength resonator is integrated at the edge of folded patch to get an additional resonance for quad-band operation. An antenna prototype is fabricated, and measured results are in good agreement with simulated results. Radiation characteristics and diversity performance of the proposed structure are presented. [ABSTRACT FROM AUTHOR]

A tri-band slot loaded microstrip antenna is proposed. The tri-band characteristics of antenna are achieved by incorporating a combination of symmetrical Y-shaped and asymmetrical U-shaped slot. The Y-shaped slot is placed symmetrically where as U-shaped slot is placed asymmetrically to the center of the patch to achieve the desired tri-band characteristics. Proposed antenna is able to achieve lower frequency ratio of 1.55 (second resonant frequency /first resonant frequency) and 1.37 (third resonant frequency/second resonant frequency), respectively. The return loss characteristics shows that the percentage impedance bandwidth achieved for global positioning system (GPS), wireless fidelity (Wi-Fi), and wireless metropolitan area networks (WiMAX) bands are 1.78%, 5.29%, and 10.37%, respectively. The parametric study of the antenna is presented. The HFSS simulated results are compared with measured and CST Microwave Studio. Good agreement is obtained between simulated and measured results. [ABSTRACT FROM AUTHOR]

A dual-band L-strip proximity fed shorted rectangular microstrip antenna is proposed and investigated theoretically simulated by HFSS and experimentally. Proposed radiating patch is located about (17.5 mm) above the ground plane. Return Loss and co- and cross polar radiation pattern are presented. Computed and measured results of return loss are in good agreement. The effect of the geometric parameters of the proposed antenna, such as length of the vertical and horizontal portion of the L-strip is also investigated. The impedance bandwidth (-10 dB return loss) 32.5% (calculated) and 33.00% (measured) for the proposed antenna are achieved for optimized antenna design. Significant size reduction (i.e., ∼85%) is obtained as compared with conventional rectangular patch of same resonant frequency. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1567–1571, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25235 [ABSTRACT FROM AUTHOR]

A wide-band L-strip proximity fed rectangular microstrip antenna is proposed and investigated both theoretically and experimentally. The radiating patch is located about 0.1λ0 (16.5 mm) above the ground plane. The broadband characteristic of antenna is achieved by employing a thick substrate (0.1λ0). Numerical results for the input impedance, VSWR, and co- and cross-polar radiation pattern are presented and compared with the measured results. Good agreement is obtained between computed and measured results. The effects of the geometric parameters of the L-strip like length of the vertical and horizontal portion of the strip are investigated. It is found that the antenna attains 48.36% impedance bandwidth (SWR ≤ 2) (theoretically) and 56.67% (experimentally) for optimized antenna design. The H-plane cross-polarization level is quite high (-16 dB) especially at (computed θ ≈ 60°, and measured θ ≈ 40°) whereas the E-plane cross-polarization level is very low. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1817–1824, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22634 [ABSTRACT FROM AUTHOR]

The theoretical and experimental investigations carried out on a gap-coupled microstrip array antenna reveal that there is a significant improvement in VSWR and bandwidth characteristics of the gap-coupled microstrip array antenna as compared with a conventional microstrip array antenna. The input impedance and the resonant frequency of the gap-coupled patch are found to depend heavily on the gap length as well as on the dielectric constant of the substrate material. [ABSTRACT FROM AUTHOR]

A new ferrite fed microstrip scanning array antenna is proposed which is capable of beam scanning in the azimuthal plane as well as in the elevation plane. The antenna consists of eight microstrip arrays, each having six elements in cascade. The antenna is fed with a ferrite loaded rectangular to circular waveguide transition. The coupling between the feed system and different arrays is achieved through slots cut in the circular waveguide. Theoretical investigations of the proposed antenna exhibit a beam scanning of ±180° in the azimuthal plane with the help of dc bias and 90° in the elevation plane for ±750MHz deviation. A scan rate of 0.06° MHz 1 is achieved for each array antenna in the elevation plane, which makes it suitable for radar. Continuous uniform beam shift is observed during scanning. [ABSTRACT FROM AUTHOR]

A small size, planar and co‐planar waveguide fed metamaterial inspired antenna is proposed for ultra‐wideband (UWB) application. The main radiating element consists of three split‐ring resonators (SRR) and placed along one axis. Moreover, coplanar waveguide (CPW)‐fed line along with modified ground plane is used to improve the impedance matching. The physical size of proposed antenna is 25(W) × 22 (L) × 1.6 (H) mm3. The CPW‐fed metamaterial inspired antenna provides bandwidth of 10.4 GHz from 3.1 to 13.5 GHz based on the 3:1 (voltage standing wave ratio [VSWR] <2). Over the range of UWB frequency, peak realized gain varies from 2.5 to 4 dBi. The proposed antenna provides omnidrectional radiation patterns. Further, fidelity factor of the proposed antenna is also calculated and measured. The calculated fidelity factor is suitable for UWB applications. Finally, prototype of the antenna is developed and tested using network analyzer. The simulated and measured results are in good agreement. [ABSTRACT FROM AUTHOR]