Gain and isolation enhancement of patch antenna using L‐slotted mushroom electromagnetic bandgap

In this paper, the application of the L‐slotted mushroom electromagnetic bandgap (LMEBG) structure to patch antenna and antenna array is investigated. A coaxial fed patch antenna and antenna array are designed at 5.8 GHz, center frequency for ISM band (5.725‐5.875 GHz). Two layers of LMEBG are placed around the patch to achieve a gain enhancement of 1.9 dB. Measured results show a bandwidth enhancement of 300 MHz with an additional resonant frequency at 5.6 GHz with 4.5 dB of gain. A 5 × 2 array of LMEBG is used to achieve a 2 dB mutual coupling reduction and 2 dB gain enhancement for a two‐element H‐coupled patch antenna array.     

Dual‐band circularly polarized aperture‐coupled stack antenna with fractal patch for WLAN and WiMAX applications

This article presents a novel circular polarized (CP) aperture coupled stack antenna for wireless local area network and worldwide interoperability for microwave access dual‐band systems. The compact stack antenna consisted of square fractal patch, aperture couple, feed line and the perturbation. The square patch is constructed with the complementary Minkowski‐island‐based fractal geometry. By way of adjusting the relevant parameters, we can obtain the dual‐band responses at 3.5 and 5.25 GHz respectively. The CP of each band are presented. The measured 10 dB return loss impedance bandwidth are 270 MHz (7.5%) for 3.5 GHz band and 450 MHz (8.6%) for 5.25 GHz band. The 3 dB axial ratio bandwidths for each bands are 1.4 and 0.76%, the polarization of radiation patterns are both left‐hand CP, and the antenna power gain are 2.84–3.1 and 0.16–2.2, dBic respectively. The proposed antenna is successfully simulated and measured with frequency responses, radiation patterns and current distributions. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:130–138, 2014.     

A two‐layer beam‐steering array antenna with 4 × 4 modified Butler matrix fed network for switched beam application

This paper presents a novel two layers beam‐steering array antenna fed by a 4 × 4 modified Butler matrix. Each of the radiation elements have been replaced by a collection of 2 × 2 circularly polarized (CP) square patches, which joined together by a modified sequentially rotated feed network. The antenna array consists of 2 × 5 CP square patches, which connected to four ring sequential rotation and fed by butler matrix. The proposed Butler matrix which plays a role as beam‐steering feed network consists of four novel 90° circular patch couplers and two 45° half circular patch phase shifter. Altogether, using of a 2 × 5 phased array antenna and a modified Butler matrix cause to empower array antenna for covering frequency range between 4.67 to 6.09GHz, the maximum gain of 14.98 dB and 3‐dB axial ratio bandwidth of 1.2GHz (4.9~6.1GHz) is attained.     

A dual‐band eight‐antenna multi‐input multi‐output array for 5G metal‐framed smartphones

A dual‐band eight‐antenna array operating in the long‐term evolution (LTE) band 41 (2.496‐2.69 GHz) and 3.5‐GHz band (3.3‐3.7 GHz) for fifth‐generation (5G) metal‐framed smartphone is presented. The proposed dual‐band antenna array is composed of four identical dual‐antenna building blocks (DABBs). Each DABB consists of two identical antenna elements with a neutralization line between them. The antenna array is simulated, fabricated, and measured. The isolations are better than 10.5 dB and 11.0 dB in the low band (LB; LTE band 41) and high band (HB; 3.5‐GHz band). The total efficiencies are 41% to 54% and 46% to 64% in the two operation bands, respectively. In addition, the measured envelope correlation coefficients are less than 0.11 and 0.06, the calculated channel capacities are better than 34.5 and 36.3 bps/Hz in the LB and HB, respectively. Furthermore, four hand‐grip scenarios are investigated, and results show that proposed antenna array can maintain excellent multiple‐input multiple‐output performances in all scenarios.     

A WiMAX circularly polarized antenna array using slot‐coupling feeding technique

In this letter, we present a circular polarization antenna array using the novel slot‐coupling feeding technique. This antenna includes eight elements which are installed in line, each array element is fed by means of two microstrip lines with equal amplitude and phase rotation of 90°. The feeding microstrip lines are coupled to a square patch through a square‐ring slot realized in the feeding network ground plane. With the presence of the slots, this antenna array is able to cover the range of frequency of 3 GHz to 4 GHz. The size of the proposed antenna array is 7λ × 1.8λ × 0.4λ. The measured gain is 15.2 dBi and the bandwidth of S11< ?10 dB is 1 GHz (3–4 GHz, 28%). The antenna array is suited for the WiMAX applications. With the use of slot‐coupling feeding technique, the measured bandwidth for axial ratio < 3 dB is about 24% in the WiMAX frequency band (3.3–3.8GHz). The measured HPBW of the y–z planes is larger than 62°. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:567–574, 2016.     

A high‐isolation dual‐polarized quad‐patch antenna fed by stacked substrate integrated waveguides for millimeter‐wave application

A high‐isolation dual‐polarized quad‐patch antenna fed by stacked substrate integrated waveguide (SIW) that is suitable for millimeter‐wave band is proposed in this paper. The antenna consists of a quad‐patch radiator, a two‐layer SIW feeding structure and two feeding ports for horizontal and vertical polarization. The two‐layer stacked SIW feeding structure achieves the high isolation between the two feeding ports (|S₂₁| ≤ ?45 dB). Based on the proposed element, a 1 × 4 antenna array with a simple series‐fed network is also designed and investigated. A prototype working at the frequency band from 38 to 40 GHz is fabricated and tested. The results indicate that the proposed antenna has good radiation performance at 38 GHz that covers future 5G applications.     

Metal‐frame‐integrated eight‐element multiple‐input multiple‐output antenna array in the long term evolution bands 41/42/43 for fifth generation smartphones

A metal‐frame‐integrated eight‐antenna array operating in the long term evolution bands 41/42/43 (2.496 GHz‐2.69 GHz, 3.4 GHz‐3.8 GHz) for future fifth generation multiple‐input multiple‐output (MIMO) applications in smartphones is presented and discussed. The proposed eight‐antenna MIMO array is formed by integrating four identical building blocks, each of which consists two dual‐mode monopole antenna elements with a neutralization line (NL) embedded in between. Part of the metal frame is exploited to increase the effective resonant length of the monopole antenna. By using the wideband NL, two transmission dips can be generated, and thus an improved isolation (>10 dB) is achieved. The proposed antenna array was simulated and experimentally tested. Good antenna efficiency (>44%) and low envelope correlation coefficient (<0.2) were obtained in the bands of interest. In an 8 × 8 MIMO system with 20 dB signal‐to‐noise ratio, the calculated ergodic channel capacity was as high as 38 bps/Hz in the low band, and 38.3 bps/Hz in the high band. Details of the proposed antenna array are described. The simulated, measured, and calculated results are presented.     

Bandwidth‐enhancement of circularly‐polarized fabry‐perot antenna using single‐layer partially reflective surface

In this article, we investigate bandwidth‐enhancement of a circularly‐polarized (CP) Fabry‐Perot antenna (FPA) using single‐layer partially reflective surface (PRS). The FPA is composed of a single‐feed truncated‐corner square patch antenna, which is covered by the PRS formed by a square aperture array. We revealed that the finite‐sized PRS produces extra resonances and CP radiations for the antenna system, which broadened the impedance matching and axial ratio (AR) bandwidths significantly. For verification, a broadband CP FPA prototype operating near 5.8 GHz was realized and tested. The fabricated antenna with overall size of 125 mm × 125 mm × 23.5 mm achieves a |S₁₁| < ?10 dB bandwidth of 31.7% (5.23‐7.2 GHz), an AR < 3‐dB bandwidth of 13.7% (5.45‐6.25 GHz), the peak gain of 13.3 dBic, a 3‐dB gain bandwidth of 22.38% (5.0‐6.26 GHz), and a radiation efficiency of >91%.     

Broadband dual‐polarized omnidirectional antenna with simple feeding structure

This paper presents a broadband dual‐polarized omnidirectional antenna with a simple feeding structure. It consists of a monopolar patch element for vertically linear polarization (VP) and a circular printed‐dipole array for horizontally linear polarization (HP). The monopolar patch antenna is loaded with shorting vias and coupled ring in order to broaden the VP bandwidth, nevertheless keeping a low profile. The printed dipoles with integrated balun are arranged on a circular substrate and incorporated with a 1‐to‐4 power divider for achieving the broadband HP omnidirectional radiation. One of the key features is to replace a shorting‐via in the monopolar patch by the coaxial line of the HP element, allowing a simple configuration and not affecting the VP radiation. The final design with a profile of 0.28λ_min has been fabricated and measured. The measurements result in an overlapped impedance bandwidth of 25.4% (2.2‐2.84 GHz) and port‐to‐port isolation of >33 dB. Also, the antenna achieves the peak gain values of 8.0 and 5.6 dBi for the VP and HP radiations, respectively.     

A compact double‐layer wideband circularly polarized microstrip antenna with parasitic elements

In this article, a new broadband circularly polarized (CP) microstrip patch antenna (MPA) with a sequential phase (SP) square‐loop feeding structure is proposed. The presented antenna is composed of a square‐loop feeding structure, four L‐shaped parasitic patches with L‐shaped slots, four parasitic square patches, and a corner‐truncated square patch. At first, a SP square‐loop is designed as a feeding structure. Then, four L‐shaped parasitic patches with L‐shaped slots are utilized to generate one CP mode by a capacitive coupled way. At last, four parasitic square patches and a corner‐truncated square patch are together placed above the SP feeding structure to broaden the circularly polarized bandwidth (CPBW). The presented antenna has a wide 3‐dB axial ratio bandwidth (ARBW) of 16.7% (5.4 GHz, 4.95‐5.85 GHz), and a wide 10‐dB return loss bandwidth of 25.5% (5.5 GHz, 4.8‐6.2 GHz). The proposed antenna features compact structure and broad 3‐AR bandwidth which could completely cover the WLAN (5.725‐5.85GHz) band. Therefore, the proposed antenna is suitable for circular polarization applications in C band.     

Circular polarized dual‐band antenna for WLAN/Wi‐MAX application

A novel square ring printed antenna has been suggested for dual‐band circular polarization (CP). The geometry contains a square patch and a square ring structure for dual‐band operation. Circular polarization is achieved using triangular cut at the boundary and right angle bend with inner perturbation. The suggested antenna is excited from the lower layer through electromagnetic (EM) coupling technique. The antenna shows good impedance bandwidths of 90 MHz (2.43‐2.52 GHz) and 800 MHz (5.7‐6.5 GHz, respectively. The antenna shows 3 dB axial ratio bandwidth of 20 MHz at lower band and 120 MHz at upper band with improved gain > 6 dBi. The simulated and measured results are well agreed with each other. The antenna is promising wideband operation at the upper band. This antenna was implemented on fiberglass reinforcement laminated Arlon substrate with dielectric constant (?_r = 2.55), and the overall physical dimension of 30 × 30 × 3.048 mm³. The designed antenna can be extensibly applicable in WLAN/Wi‐MAX communication. The presented antenna is designed using hyperlynx IE3D and the simulated results are presented.     

A new broadband circularly polarized square‐slot antenna with low axial ratios

A new broadband circularly polarized (CP) square‐slot antenna with low axial ratios is proposed in this article. The antenna is comprised of an L‐shaped microstrip line with tapered section and a square‐slot ground plane with some stubs and slots, which are utilized as perturbations for the desirable antenna performance. By loading stubs and slots in the square‐slot ground plane, the 2‐dB axial ratio bandwidth (ARBW) and 10‐dB return loss bandwidth for the presented antenna can be markedly improved. The measured results show that its 2‐dB ARBW is 4.2 GHz (54.2% from 5.65 GHz to 9.85 GHz) and its 10‐dB return loss bandwidth is about 8.9 GHz (92.7% from 5.15 GHz to 14.05 GHz). The proposed antenna features compact structure and broad 2‐AR bandwidth which could completely cover the WLAN (5.725‐5.85 GHz) band. Therefore, the proposed antenna is suitable for circular polarization applications in C band.     

Ka‐band phased patch array antenna integrated with a PET‐controlled phase shifter

In this article, a 4 × 4 linear‐phased patch array antenna, consisting of four 1 × 4 patch subarrays and a true time‐delay multiline phase shifter, is proposed on a thin film liquid crystal polymer substrate at Ka‐band. The patch antenna is designed with a gain of 6 dBi at 35 GHz and a bandwidth of 23% centered at 35 GHz. To enhance the gain and symmetrize the beam patterns of the 4 × 4 array, a 1 × 4 patch subarray in the E‐plane was designed and characterized. The subarray produces an enhanced gain of 11 dBi and a wide beamwidth of ±38° in the H‐plane for beam steering. The proposed phase shifter comprises a 1 × 4 microstrip line power splitter and a piezoelectric transducer‐controlled phase perturber. A large phase variation of up to 370° and a low insertion loss of less than 2 dB were demonstrated for the phase shifter at Ka‐band. The integrated phased array attains a gain of 15.6 dBi, and a continuous true‐time delay beam steering of up to 33 ± 1° from 31 to 39 GHz. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:199–208, 2016.     

2D circularly polarized antenna array fed by spoof surface plasmonic waveguide

A two‐dimensional high‐gain circularly polarized (CP) patch array antenna operating in Ku band is proposed in this article. To excite a novel spoof surface plasmonic transmission line (SSP‐TL), which is mounted vertically on the ground, a waveguide with a transition are used for the momentum and impedance matching. A SSP‐TL 4‐way power divider is then used to feed a 4 × 7 circular patch array by travelling waves. Therefore, the CP radiation is generated on the patches located between the parallel SSP‐TLs. Avoiding the deterioration in axial ratio, 90° phase difference between adjacent SSP‐TLs is designed by tuning the height of the SSP‐TLs, as the dispersion property is influenced by the height of the corrugations obviously. The simulated maximum gain of 20.6 dBi is achieved at 15.2 GHz, together with the axial ratio of 0.8 dB. A prototype is fabricated and measured to validate the proposed antenna array.     

Dual‐band dual‐polarized compact planar monopole antenna for wide axial ratio bandwidth application

In this article, a geometrically simple, microstrip line‐fed planar monopole structure with slanting edge ground plane is designed to realize the dual‐band dual‐polarized operation. The proposed antenna consists of a rotated U‐shaped patch and an electromagnetically coupled L‐shaped parasitic radiating element. Owing to the combination of microstrip line‐fed radiating patch and a slanting‐edge rectangular ground plane on the opposite side of the substrate, the proposed dual‐band antenna can generate broad axial ratio bandwidth (ARBW) in the upper frequency band. The overall dimension of the prototype is only 32 × 32 × 1.6 mm³. The measured results validate that the proposed antenna has two operational frequency bands, 29.84% (1.54‐2.08 GHz) for linearly polarized radiation and 71.85% (3.96‐8.4 GHz) for circularly polarized radiation. Measured result shows that 3‐dB ARBW of the proposed antenna is 73.54% (3.80‐8.22 GHz) in the higher frequency band. It shows that the higher frequency band exhibits a left‐hand circularly polarized radiation in the boresight direction.     

Enhancement of gain with corrugated Y‐shaped patch antenna for triple‐band applications

In this article, investigation has been carried out on Y‐shaped patch antenna to produce triple‐band for wireless applications. The corrugated Y‐shaped patch antenna is considered to produce low reflection coefficient with high gain at the triple‐bands. The corrugated Y‐shaped patch antenna is resonates at 4.19 GHz (4‐4.43 GHz), 8.79 GHz (8.61‐9.01 GHz), 13 GHz (12.6‐13.6 GHz) frequencies with reflection coefficient of ?29.26 dB, ?34.87 dB, ?40.37 dB and gain 5.01 dBi, 5.42 dBi, 7.46 dBi, respectively. The proposed corrugated Y‐shaped patch antenna works three frequency bands at radio communications, satellite communications, and aeronautical radio navigation applications, respectively.     

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.     

Circularly polarized stacked patch antenna array with enhanced bandwidth for S‐band applications

In this article, a circularly polarized coupled slot 1 × 4 stacked patch antenna array with enhanced bandwidth is proposed for S‐band applications. Initially, a patch antenna radiating at 2.79 GHz is designed and maximum energy from feedline to patch element is coupled using two rectangular slots. Whereas, a parallel feedline structure is designed to provide polarization flexibility by creating 0, 90 , and 180^o phase differences. Then, a truncated patch element is vertically stacked in the design to achieve broader bandwidth of 600 MHz over frequency range from 2.4 to 3.0 GHz. Finally, a coupled slot 1 × 4 array stacked antenna array having feedline line structure to provide 90^o phase difference for circular polarization is designed and fabricated for measurements. It is observed that the final design achieved target specification having impedance matching (|S₁₁ | (dB) < ?10 dB over 2.4 to 3.0 GHz, broad band circular polarization, and 11.5 dBic total gain. Overall, a good agreement between simulated and measurement results is observed.     

Complementary meander‐line‐inspired dielectric resonator multiple‐input‐multiple‐output antenna for dual‐band applications

The communication presents a simple dielectric resonator (DR) multiple‐input‐multiple‐output (MIMO) dual‐band antenna. It utilizes two “I”‐shaped DR elements to construct an “I”‐shaped DR array antenna (IDRAA) for MIMO applications. The ground plane of the antenna is defected by two spiral complementary meander lines and two circular ground slots. In the configuration, two “I”‐shaped DR elements are placed with a separation of 0.098λ. The antenna covers dual‐band frequency spectra from 3.46 to 5.37 GHz (43.26%) and from 5.89 to 6.49 GHz (9.7%). It ensures the C‐band downlink (3.7‐4.2 GHz), uplink (5.925‐6.425 GHz), and WiMAX (5.15‐5.35 GHz) frequency bands. Each DR element is excited with a 50‐Ω microstrip line feed with aperture‐coupling mechanism. The antenna offers very high port isolation of around 18.5 and 20 dB in the lower band and upper band, respectively. The proposed structure is suitable to operate in the MIMO system because of its very nominal envelope correlation coefficient (<0.015) and high diversity gain (>9.8). The MIMO antenna provides very good mean effective gain value (±0.35 dB) and low channel capacity loss (<0.35 bit/s/Hz) throughout the entire operating bands. Simulated and measured results are in good agreement and they approve the suitability of the proposed IDRAA for C‐band uplink and downlink applications and WiMAX band applications.     

A compact dual‐band 2 × 1 metamaterial inspired mimo antenna system with high port isolation for LTE and WiMax applications

This article proposes a compact (43 × 26 × 0.8 mm³) dual‐band two‐element metamaterial‐inspired MIMO antenna system with high port isolation for LTE and WiMAX applications. In this structure, each antenna element consists of a square–ring slot radiator encircling a complementary split ring resonator. A tapered impedance transformer line feeds these radiating apertures and shows good impedance matching. A 2 × 3 array of two‐turn Complementary Spiral Resonator structure between the two antenna elements provides high dual‐band isolation between them. The fabricated prototype system shows two bands 2.34 – 2.47 GHz (suitable for LTE 2300) and 3.35 – 3.64 GHz (suitable for WiMAX). For spacing between two antennas of 10 mm only, the measured isolation between the two antenna elements in the lower band is around ?32 dB while that in the upper band is nearly 18 dB. The system shows a doughnut‐shaped radiation patterns. The peak measured antenna gains for the proposed MIMO system in the lower and higher bands are 3.9 and 4.2 dBi, respectively. The MIMO system figure of merits such as the envelope correlation coefficient, total efficiency are also calculated and shown to provide good diversity performance.