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Due to limited antenna space, high communication requirements, and strict regulatory constraints, the design of antennas for modern mobile phones has become an exceedingly challenging task. In recent years, numerous studies have been conducted in this area, leading to significant advancements. This review paper comprehensively summarizes recent progress made in antenna design for modern mobile phones. Firstly, the challenges faced in antenna design for modern mobile phones are described, including bandwidth enhancement, integration and decoupling techniques, mm-wave array antennas, satellite communication antennas, as well as interactions between mobile antennas and the human body. Secondly, the basic antenna types (such as inverted-F, slot, loop, and planar inverted-F antennas) commonly used in modern metal-bezel mobile phones along with their key characteristics are briefly summarized. Thirdly, the commonly exployed methods used in practical applications for designing wideband antennas within compact sizes and achieving decoupling among multiple antennas with wide bandwidths are collected. Fourthly, recent advances in the design of compact, wideband, and wide-angle scanning mm-wave arrays for modern mobile phones are summarized. Fifthly, recent progress made in satellite communication antenna designs for modern mobile phones, including broadside and end-fire radiation patterns, is presented. Sixthly, recent studies on the interaction between mobile antennas and the human body are briefly concluded. Finally, the future challenge of antenna design for mobile phones is briefly discussed. It is our hope that this comprehensive review will provide readers with a systematic understanding of antenna design principles applicable to modern mobile phones.

This paper presents a dual‐band multiple‐input multiple‐output (MIMO) antenna pair for 5G cell phones. The antenna pair consists of two planar concave antenna elements that are tightly arranged on a vertical substrate. By adding capacitors to form a resonant network, an additional operating mode is excited, resulting in dual‐band performance. The resonant frequency of the additional mode can be adjusted independently by changing the capacitance value. Moreover, a neutralization line is used to improve the isolation of the high band without affecting the low band. The antenna pair occupies a small area of 13.2 × 6.3 mm2 and operates at both 3.5 and 4.85 GHz bands. The isolations are better than 17 dB at the 3.5 GHz band and better than 19 dB at the 4.85 GHz band. The proposed dual‐band antenna pair might be a good choice for 5G terminals. [ABSTRACT FROM AUTHOR]

Health and safety concerns have grown in recent years due to the increasing frequency bands and the demand for wireless communication apparatus. Electromagnetic (EM) radiation breakthrough from Radio frequency (RF) into the human head is an issue that needs to be addressed. Radiation from RF sources can cause serious biological hazards inside the human body. This study measures the average Specific Absorption Rate in a 7-year-old child's head tissues using the ANSYS HFSS software and varying the distance from the source to the antenna in order to address these issues. SAR levels of phones sold should be below certain standard limits. We have used an internal antenna of a mobile phone It's a planar inverted F-antenna (PIFA) with a connected feeding structure.

In this paper, a reconfigurable metal rim antenna with a small clearance and compact structure for 4G/5G smartphones is proposed. It consists of the system ground plane and a metal rim with two slits, in which a U-shaped slot of 1 mm (the smallest) clearance is realized between the system ground and metal rim. The theory of characteristic modes is applied to analyze the eigenmodes of the antenna so as to aid the optimum design. The characteristic modes (CMs) in the band of interest are studied, and an inductive coupling exciter is identified as the best since three CMs can therefore be generated in the lower frequency band (0.69-0.96 GHz), and an SP4T switch can be utilized to increase the bandwidth of the whole lower band. A prototype antenna of the optimized design was fabricated. A good agreement was obtained between the measured and simulated results. The 6-dB frequency bands are the lower band (0.69-0.96 GHz), the middle band (1.7- 2.7 GHz), and the higher 5G band (3.4- 3.6 GHz), respectively, and the total efficiencies are over 50% in all these frequency bands. They indicate that the antenna is a very good candidate for smartphone applications.

A novel antenna design with a low specific absorption rate (SAR) is introduced. The antenna has a very low profile and it is designed to be placed on the back cover of a mobile device at around 2 GHz. The solution is based on nested loops which distribute the field over a large volume so that the maximum SAR value remains relatively low in the user’s tissue. The proposed design also provides relatively good efficiency, considering the extremely low profile, and the close proximity of lossy human tissue and the phone’s main body. The manufactured prototype exhibits almost 50% lower maximum SAR than a patch antenna used as a reference.

In this article, the effect of an isolator in a multiple‐input multiple‐output (MIMO) antenna is analyzed in terms of its efficiency and isolation. An isolator is frequently utilized in MIMO antennas; however, the use of an isolator can aggravate the bandwidth or efficiency performance even though its isolation performance is improved. To develop a way of applying an isolator without sacrificing the bandwidth or efficiency performance, it is important to note that the characteristic modes excited by the MIMO antenna are related to the performance of the isolator. Two MIMO antenna systems using different ground characteristic modes are implemented to analyze the effect of the isolator. Via the isolator, both MIMO antennas achieved improved isolation, but the reference antenna underwent severe bandwidth degradation and efficiency degradation (from 31.81% to 16.69%), whereas the proposed antenna had relatively smaller reductions in bandwidth and efficiency (from 53.14% to 46.87%). [ABSTRACT FROM AUTHOR]

In recent years, the screen-to-body ratio of mobile handsets has been increasing. Today, the screen nearly fills up the entire front side. Conventionally, the screen is mainly seen as a metallic object that adversely affects antenna performance. In this paper, the large screen is used for the first time to facilitate an additional uncorrelated MIMO port in a tri-port design, for several LTE bands below 1 GHz. To this end, the screen and the terminal chassis are modeled as two metal plates and their characteristic modes are analyzed. Four modes are then tuned to resonance and selectively excited to yield three uncorrelated MIMO ports. Simulation and measurement results are in good agreement. The measured bandwidths are 23%, 17% and 21%. Within the operating band, the measured isolation is above 13 dB, envelope correlation coefficient below 0.16 and average total efficiency above 72%.

This letter presents a wideband compact dual-polarized antenna with endfire radiation pattern for the fifth-generation millimeter-wave (mm-wave) applications. The antenna achieves a –10 dB S11 bandwidth of 16.5% (25–29.5 GHz). The antenna has a thickness of 1.6 mm and a clearance of 3.4 mm. The presented four-element array achieves a maximum realized gain of 9.9 and 9.1 dBi for horizontal mode (H-mode) and vertical mode (V-mode), respectively. The antenna has a wide beamwidth in both elevation and azimuth planes with good scanning performance for both H-mode and V-mode. [ABSTRACT FROM AUTHOR]

In this paper, 4 × 4/8 × 8/10 × 10 multiple input multiple output (MIMO) antenna systems composed of co-located self-neutralized antenna pairs are proposed to operate at 4.8-5.0 GHz (part of N77 band) for the fifth-generation (5G) communication applications. The proposed antenna pairs consist of a loop antenna and a monopole antenna, co-locating together with a compact size of 6.7 × 15.5 ×3.08 mm3. Meanwhile, the co-located design can miniaturize 50% of the antenna size, which is quite significant for practical mobile applications with limited space environment. In addition, the adoption of the self-neutralization technique between the co-located loop antenna and the monopole antenna contributes to a satisfactory isolation with better than 25/20/16.5 dB for the 4 × 4/8 × 8/10 × 10 MIMO systems respectively. Analysis of the isolation improvement is also discussed in this study. Moreover, the antenna pairs are able to generate complementary radiation patterns, enabling the envelope correlation coefficients (ECC) between the antennas to be less than 0.1. Also, efficiencies of the MIMO antenna system achieve up to 60% as there is no external decoupling structure deteriorating the radiation performance of the proposed antenna pairs. Finally, a 4 × 4 MIMO antenna system prototype is fabricated and measured to verify its prospect for 5G MIMO applications.

A novel wideband millimeter (mm)‐wave antenna integrated with a multi‐input multi‐output (MIMO) antenna is presented for fifth‐generation (5G) applications. The proposed model consists of a 2 × 1 array‐based single‐element wideband antenna for mm‐wave applications, and a 2‐element strip‐based MIMO antenna system for sub‐6‐GHz band applications. In the ground plane, two clearance regions were etched to improve the impedance matching of MIMO elements while an open‐circuit rectangular tuning stub is attached to the mm‐wave antenna feed line to broaden its impedance bandwidth. The dimensions of the used panel are 100 × 60 × 0.8 mm3, which are among the typical dimensions used in mobile terminals. The mm wave antenna covers the frequency ranges from 25.08 to 28.08 GHz, while the frequencies from 2.88 to 4.58 GHz and from 5.15 to 6.15 GHz are covered by the MIMO antenna. Depending on the experimental results achieved, the suggested design might be considered a successful candidate for 5G applications, with wideband characteristics, excellent field correlation, and high gain functionality. [ABSTRACT FROM AUTHOR]

The study results of parameters of main high-frequency range mobile antennas are presented: whip antenna, sloping wire antenna, inverted V symmetrical vibrator (dipole), T-shaped antenna, sloping V antenna, NVIS, traveling wave antenna, λ-shaped antenna. The analysis of the input active and reactive resistances of the antennas, as well as standing wave ratio is performed depending on the frequency. The corresponding graphical dependencies are presented.

This research presents a far-field (FF) antenna with near-field communication (NFC) capability for 3G/4G/LTE mobile devices. The integrated farand near-field communication (FNFC) antenna was fabricated using conductive silver ink on polyethylene terephthalate (PET) flexible substrate. The FF segment of the antenna is operable in the frequency range of 1.8-2.1 GHz, and the NFC antenna is of dual loop and operable at 13.56 MHz. In the antenna realization, simulations were performed and, to validate, an antenna prototype was fabricated. The experimental results revealed that the FF antenna achieved an impedance bandwidth of 37% (1.52-2.21 GHz), given |S11| of less than -6 dB, with the minimum and maximum efficiency of 92.1% and 98%. The experimental gains are 1.76-2.08 dBi across the target operating frequency band, with near-omnidirectional radiation pattern. The simulation and experimental results are in good agreement. Moreover, the FNFC antenna achieves strong magnetic field distributions in Hx, Hy, and Hz orientations and holds promising potential for 3G/4G/LTE applications.

In this paper, we introduce a ground radiation antenna that uses controlled endless metal rim modes. In the proposed technique, the metal rim mode is tuned and excited as a one‐wavelength radiator by a small ground radiation antenna. The proposed antenna occupies a clearance of 1 mm × 4 mm in a 30 mm × 20 mm ground plane. A metal rim with dimensions of 34 mm × 24 mm surrounds the ground plane, and the metal rim is separated from the ground plane by a gap of 2 mm. In addition, a lumped capacitor is inserted between the metal rim and the ground plane to control the characteristic mode of the metal rim such that the resonance of the metal rim is tuned to be equal to the operating frequency. By performing simulations and measurements, we compare the performance of the proposed antenna with that of a reference antenna that does not have an inserted capacitor between the metal rim and the ground plane. The results show that a significant improvement of the radiation performance is obtained by employing the proposed technique.

In this article, a miniaturized wide‐band and dual‐band loop‐type ground radiation antenna for mobile devices is proposed. The antenna feed structure, which consists of two shunt capacitors and a shunt inductor, enhances the bandwidth in both bands by generating an additional parallel feeding resonance in each band. Compared to the reference dual‐band loop‐type ground radiation antenna with a single loop feed that only uses a capacitor in series, the bandwidth of the proposed antenna is 1.6 and 2.13 times wider in the low and high bands, respectively under a 3:1 voltage standing wave ratio. The measured results indicate that the proposed antenna provides good radiation performance. [ABSTRACT FROM AUTHOR]

In this article, a wideband loop‐type ground radiation antenna is proposed for USB dongle applications. Wide bandwidth has been achieved using the orientation of the antenna embedded in the ground plane along with the impedance level of the feed structure. The ground clearance of the antenna is utilized so that the ground mode is tuned to the mid‐band frequency. The impedance level is controlled by using a series combination of a lumped inductor and a capacitor in the feed loop of the antenna. A good agreement between measured and simulated results has been observed. The measured bandwidth and peak total efficiency of the antenna are 1180 MHz and 88.27%, respectively. [ABSTRACT FROM AUTHOR]

In this study, we introduce a dual-band ground radiation antenna using an endless metal-rim mode control method that operates in the WLAN band. In the proposed antenna, the metal-rim modes are excited as one- and two-wavelength-mode radiators by a dual-band ground radiation antenna, which occupies a small space on the ground plane. The metal rim surrounds the ground plane with a gap of only 2 mm. In addition, two capacitors are inserted between the ground plane and the endless metal rim to control the one- and two-wavelength modes of the endless metal rim. Based on simulation and measurement results, we noted that the proposed antenna has an impressively high radiation performance. [ABSTRACT FROM AUTHOR]

In this article, a compact composite right/left-handed wideband antenna has been proposed and analysed using finite-difference time-domain for cellular applications. The proposed antenna operates at different wireless standards such as GSM1800, WCDMA, WiMAX, Bluetooth and Wi-Fi. It exhibits wideband behaviour with a bandwidth of 55% (at 2.46 GHz). The proposed antenna is compact and has a radiating element size of 0.14 λo × 0.22 λo × 0.01 λo. In addition, commercial Ansys HFSS software has been used to verify the results and a prototype has also been fabricated to test the antenna experimentally. The proposed metamaterial antenna offers good radiation characteristics and is omni-directional in xz-plane with an average gain of 1.3 dBi in the operating bandwidth. [ABSTRACT FROM AUTHOR]

A compact beam-steerable antenna array is proposed for 28 GHz mobile terminals. The proposed array consists of one active element and two passive parasitic elements. Two switches are utilized in the design instead of phase shifters. Each parasitic element can be terminated with short-circuited transmission lines of different lengths via one switch. By controlling the two switches, different reactive impedance is loaded on two parasitic elements. The radiation pattern of the active element can be scattered into different directions by two parasitic elements. The switching loss is studied, where two switches with 2.8 dB loss cause less than 1.82 dB loss for the whole array. The small array locations on the chassis are also investigated. The designed array is smaller than 0.81 wavelength, and covers the band of 28–29 GHz with the scan angle ≥±90°. By placing two arrays on each long chassis edge, 360° beam steering can be realized. Surface currents on the chassis are efficiently excited to achieve high gain with the small array. Measurements are carried out and align well with simulations. In practical applications, several small arrays can be implemented on the metal back cover and around a cellphone to combat users’ mobility. [ABSTRACT FROM AUTHOR]

Abstract In this paper, we present a novel narrow-frame antenna with a size of 75 × 8 × 5.8 mm3 for 5.7 in. mobile phones. The antenna mainly consists of a monopole with four branches that are coupled to a two-branch grounded strip. Our antenna is able to cover more bands than other narrow-frame antennas by excitation of several resonant modes. The improved range of the antenna covers the following eleven bands: LTE700, GSM850, GSM900, DCS, PCS, UMTS, LTE2300, LTE2500, LTE3400 (3400–3800 MHz)/WiMAX3.5 GHz (3400–3650 MHz), WLAN5.2 GHz (5150–5350 MHz) and WLAN5.8 GHz (5725–5875 MHz). Another advantage of the proposed antenna is that it does not need any lumped element to match the antenna. The working principles of the proposed antenna are thoroughly studied. A prototype of the proposed antenna is fabricated and measured, with the results in good agreement with the simulation results. [ABSTRACT FROM AUTHOR]

Abstract: This letter presents an orthogonal mode 4‐antenna system operating in the 3.5‐GHz band (3.3–3.6 GHz) for the fifth‐generation (5G) multiple‐input multiple‐output (MIMO) mobile device. The 4‐antenna system is composed of 2 identical tightly arranged antenna pairs, and each pair is formed with an arrow‐shaped monopole and a bended dipole with gap‐coupled feeding. The tightly‐arranged antenna pair is face‐to‐face arranged on the front and back side of the substrate and the distance between the center of the 2 elements is only 1 mm; however, they have good isolation (better than 10 dB) and diversity performance (envelope correlation coefficient better than 0.11) with the help of orthogonal mode. This configuration provides promising solution for compactness of the MIMO antenna in mobile phone. The prototype was fabricated and measured, and the measured results show good agreements with the simulated ones. [ABSTRACT FROM AUTHOR]

In this paper, we introduce a ground radiation antenna that uses controlled endless metal rim modes. In the proposed technique, the metal rim mode is tuned and excited as a one‐wavelength radiator by a small ground radiation antenna. The proposed antenna occupies a clearance of 1 mm × 4 mm in a 30 mm × 20 mm ground plane. A metal rim with dimensions of 34 mm × 24 mm surrounds the ground plane, and the metal rim is separated from the ground plane by a gap of 2 mm. In addition, a lumped capacitor is inserted between the metal rim and the ground plane to control the characteristic mode of the metal rim such that the resonance of the metal rim is tuned to be equal to the operating frequency. By performing simulations and measurements, we compare the performance of the proposed antenna with that of a reference antenna that does not have an inserted capacitor between the metal rim and the ground plane. The results show that a significant improvement of the radiation performance is obtained by employing the proposed technique. [ABSTRACT FROM AUTHOR]

The need for on-line information in any environment has led to the development of mobile satellite communication terminals. These high data-rate terminals require inertial antenna pointing error tolerance within fractions of a degree. However, the base motion of the antenna platform in mobile applications complicates this pointing problem and must be accounted for. Gimbaled motorised pedestals are used to eliminate the effect of disturbance and maintain uninterrupted communication. In this paper, a three-axis ship-mounted antenna on a pedestal gimbal system is studied. Based on the derived dynamic model of the antenna pedestal multi input-multi output PID andH∞linear controllers are designed to stabilise the antenna to keep its orientation unaltered towards the satellite while the sea waves disturb the antenna. Simulation results are presented to show the stabilisation performance of the system with the synthesised controllers. It is shown through performance comparison and analysis that the proposedH∞control structure is preferable over PID controlled system in terms of system stability and the disturbance rejection. [ABSTRACT FROM PUBLISHER]

A compact slot multiple-input multiple-output Antenna (CSMA) for smartphones with metal housing is proposed in this paper. The antenna has a slot radiator shared between two input ports and a T-shaped defect-ground slot (DGS) for decoupling. A function for selecting the best dimensions of the DGS for optimum decoupling is derived using the transmission theory. The CSMA antenna is designed using simulation to operate in the 2.4-GHz wireless-area-network (WLAN) system and then fabricated for measurement. Measured results show that the antenna has an impedance bandwidth (IMBW) of 2.4–2.48 GHz, mutual coupling from −19 to −29 dB and envelope-correlation coefficient (ECC) below 0.0867 within the IMBW. The antenna is very easy to fabricate and is a potential candidate for the MIMO smartphones antennas with metal housing. [ABSTRACT FROM PUBLISHER]

This communication presents a planar ultra-wideband multi-input multi-output antenna with pattern diversity and isolation improvement based on the theory of characteristic modes. The proposed antenna (for new-generation wireless mobile terminals) consists of two ultra-wideband antenna elements—a compact quarter loop and a circular planar monopole located on the opposite edges of a rectangular ground plane. These two antenna elements are able to excite different modes in the ground plane and thus realize the desired diverse radiation patterns and high isolation without any additional decoupling structures. The experimental results show that both antenna elements are ultra-wideband with impedance bandwidths (return losses more than 6 dB for the quarter-loop antenna and more than 10 dB for the circular planar monopole antenna) of 130% (2–9.5 GHz). The isolation is over 20 dB with a peak value of 50 dB. The realized gains are above 1.5 dBi. The total efficiencies are above 70%. The envelope correlation coefficient is less than 0.03 assuming that the antenna operates in an isotropic channel. [ABSTRACT FROM AUTHOR]

This paper presents a multiple input multiple output (MIMO) antenna for multiband operation based on meander lines with L shaped metallic strip. Meander lines is basically a monopole antenna loaded with multiple sections of short circuited transmission line that acts as inductor and alter the impedance characteristics of antenna. Antenna size miniaturization of 69 % has been achieved by placing double U slots on the ground plane and a line slot DGS (Defective Ground Structure) is used to reduce the mutual coupling between the antenna elements. The values of envelope correlation coefficient (ECC) and Specific Absorption Rate (SAR) lie well below the specified limit. [ABSTRACT FROM AUTHOR]

A mobile satellite communication antenna is a device installed on a moving carrier for mobile satellite communication. Gimballed motorized pedestals are used to eliminate the effect of disturbance and maintain uninterrupted communication when the carrier is moving. Mobile satellite communication antennas are becoming increasingly more popular due many advantages of mobile satellite communication. In this paper, a three-axis ship-mounted antenna on a pedestal gimbal system is studied. We study the problem with a different perspective and method from the previous work for two-axis antenna pedestals. The former studies treat the subsystems to be isolated and design controllers separately, which neglect the coupling effects in the dynamics of two or three-axis antenna pedestal gimbals. We treat three sub-systems as a whole and derive the dynamic model of the system using the Newton–Euler method. Based on the dynamic model, linear PI controllers are designed to stabilize the antenna to keep its orientation towards the satellite. The design objective of the control system is to direct the on-board antenna toward a satellite and to keep its orientation unaltered despite the effect of sea waves disturbing the antenna. Simulation results are presented to show the stabilization performance of the system with the synthesized controllers. [ABSTRACT FROM AUTHOR]

Measuring multiple-input multiple-output (MIMO) specific absorption rate (SAR) is an important part of mobile handset evaluation, following the introduction of uplink MIMO transmission schemes in long-term evolution advanced systems. However, the measurement of MIMO-SAR is complex and time consuming. In this communication, six unique dual-antenna mobile handsets, including both typical and novel designs, are analyzed to determine the dependence of MIMO-SAR on antenna configuration and correlation. It is found that, for certain antenna configurations, the location of the maximum MIMO-SAR and the corresponding relative phase between the ports can be predicted. This can be applied to drastically reduce measurement time. In addition, dual antennas with low envelope correlation coefficients in the radiation patterns also offer near-orthogonal electric near fields. This leads to smaller MIMO-SAR than stand-alone SAR (S-SAR) over all relative phases, making MIMO-SAR measurement unnecessary. The results also provide guidelines for designing multi-antenna handsets with low SARs. For verification, the S-SAR and MIMO-SAR at a relative phase of 0° were measured for several prototypes. The measured SAR distributions showed good agreement with the simulated ones. [ABSTRACT FROM AUTHOR]

A wideband planar double-segmented loop antenna that can excite different modes with perpendicular polarized omnidirectional radiation patterns is designed for mobile platforms. The proposed antenna combines these resonant modes with adjacent resonant frequencies for wideband application. One of the modes is induced by the loop element itself and generates horizontally polarized radiation pattern. Meanwhile, the other mode generates vertically polarized radiation pattern when the ground plane is excited by the loop element and operates as a radiator. The measured results confirm that the antenna is capable of achieving wide bandwidth (10-dB return loss) from 2.1 to 2.9 GHz (the corresponding fractional bandwidth is 32%). The average total realized gain of the antenna is 2.75 dBi over the entire operating bandwidth. [ABSTRACT FROM PUBLISHER]

In this paper, the effect of coupling between the antenna and ground characteristic mode is investigated by comparing the radiation performance of antennas located inside and outside the ground plane. In general, it is understood that an antenna occupying a larger space has better radiation performance. However, in this paper, it is shown that coupling between the antenna and ground is important for radiation performance, rather than the size occupied by the antenna. The antenna is strongly coupled with the ground characteristic mode when located inside the ground; the −10 dB bandwidth is 130 MHz at 2.45 GHz, and the measured realized efficiency is −0.64 dB in the 2.4‐2.5 GHz band. When the antenna protrudes from the ground plane, the coupling between the antenna and the ground characteristic mode is weak, achieving a narrower −10 dB bandwidth of 50 MHz at 2.45 GHz, and lower measured realized efficiency of −2.20 dB in the 2.4‐2.5 GHz band. In other words, the radiation performance of the same antenna is significantly influenced by the coupling with the ground. [ABSTRACT FROM AUTHOR]

ABSTRACT An estimation method for the total radiation power (TRP) and radiation pattern of mobile antennas embedded in mobile phones using a planar near-field scanning method is proposed. The tangential magnetic fields on both front and rear faces of a mobile phone are measured both in magnitude and phase using a dual-probing technique in the time-domain. Moreover, for accurately obtaining the phase information from the measured data in the time-domain, a reliable triggering technique is introduced. The far-field is calculated by using the near-field to far-field transformation based on the equivalent principle and the image method. The calculated TRP and radiation pattern are validated by comparison with the measured TRP and radiation pattern in an authorized anechoic chamber, and good agreement has been achieved. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1437-1443, 2016 [ABSTRACT FROM AUTHOR]

ABSTRACT The article reveals the design of a metamaterial cell inspired triple band antenna for DCS 1800, PCS 1900, WCDMA, Bluetooth, WLAN 2400, WiMAX 2.5, and WLAN 5 GHz frequency band applications. The overall antenna size is 48 × 48 × 1.575 mm3 where the electrical dimension is 0.26 λ × 0.26 λ × 0.0084 λ at 1.6 GHz lower frequency band. The proposed antenna consists of a microstrip feed line and metamaterial unit cell providing a negative index of refraction, which indicates both negative magnetic value of permeability and negative electrical value of permittivity. The proposed antenna achieves triple −10 dB measured impedance bandwidth of 370 MHz (1.6-1.97), 380 MHz (2.34-2.72), and 1.48 GHz (3.89-5.37). The measured gain of the proposed antenna at 1.9 GHz is 1.64 dB, 2.45 GHz is 2.07 dB, and 5 GHz is 4.06 dB with radiation efficiency of 66.2%, 77.15%, and 87.6%, respectively. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:263-267, 2016 [ABSTRACT FROM AUTHOR]

An octa-band WWAN/LTE monopole antenna with a size of 80\,\textmm \times 8\,\textmm \times 5.8\,\textmm for 5.7-inch mobile phones is proposed and studied. The proposed antenna consists of a folded metal plate with a lumped-element high-pass matching circuit. The working mechanism is analyzed based on the S-parameters and the surface current distributions. The 0.25-wavelength, 0.5-wavelength, and 1-wavelength modes of the monopole antenna are excited and used. The attractive merit of the proposed antenna is that the height of the nonground portion is only 8 mm. A prototype is fabricated and measured. Its measured -6\;\textdB impedance bandwidths are 290 MHz (0.69–0.98 GHz) and 1.11 GHz (1.63–2.74 GHz) which cover the LTE700, GSM850, GSM900, GSM1800, GSM1900, UMTS, LTE2300, and LTE2500 bands. Within the two frequency bands, good radiation performances are obtained. [ABSTRACT FROM AUTHOR]

In this communication, a compact frequency reconfigurable antenna for LTE/WWAN mobile handset applications is proposed. The proposed antenna mainly consists of radiating elements and two PIN diodes. In addition, the antenna has a simple structure with a compact size of 36.5 \times 10\;\textmm^2. This antenna operates in six modes, and each mode is given a different resonant pathway by adjusting the bias states of two PIN diodes. When PIN diodes #1 and #2 are in the on and off states, respectively, the proposed antenna can cover the LTE700 (698–787 MHz) band by operating in mode 1. Moreover, the wide bandwidth in a higher band formed by combining modes 2 and 3 can cover the LTE2300 (2305–2400 MHz) and LTE2500 (2500–2690 MHz) bands. When PIN diodes #1 and #2 are in the off and on states, respectively, a resonant frequency in the lower band is formed by integrating modes 4 and 5. This can cover the GSM850 (824–894 MHz) and GSM900 (880–960 MHz) bands. When the two PIN diodes are in the on state, the proposed antenna can cover the GSM1800 (1710–1880 MHz), GSM1900 (1850–1990 MHz), and UMTS (1920–2170 MHz) bands in operating mode 6. [ABSTRACT FROM PUBLISHER]

ABSTRACT A multiband coupled-fed printed antenna with compact branch structure for 4G mobile phone is proposed in this letter. The antenna has a planar structure with a small board space of 15 × 29 mm2. A driven monopole strip and a coupled branch-strip are developed on different sides of a thin FR4 substrate to produce different operation bands. The antenna can operate in octa-bands, including GSM850, GSM900, DCS1800, PCS1900, UMTS, LTE2300, LTE2500, and WLAN, with the return losses more than 6 dB. A prototype of the proposed antenna is fabricated, and its measured results including return losses, efficiencies, and gains are presented. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2289-2294, 2015 [ABSTRACT FROM AUTHOR]

ABSTRACT A design approach of multiband and wideband antennas for radio communication devices is presented. The antenna is consisted of a monopole, a folded loop, and a helix. The fundamental behaviors of the single element and their combinations are analyzed to give desired bandwidths per the mutual coupling between elements. The ground plane dimension and the device thickness are considered. The study has a focus on the UHF and lower microwave range to support most of civilian applications. The presented antenna structure is a good starting point to be familiar with the multiband antenna design as the antenna can be configured to cover a wide frequency range to support cellular telephony, GPS, wireless local networking on so forth. A radio communications device incorporating such antennas is also described. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1718-1723, 2015 [ABSTRACT FROM AUTHOR]

ABSTRACT In this letter, a metamaterial (MTM) inspired antenna is designed to operate at DCS, GSM1800, WCDMA, and Bluetooth and hence shows good potential to be used in mobile applications. The proposed antenna shows n characteristics with first band (1.61-1.84 GHz) resonant at 1.72 GHz and second (2.08-2.5 GHz) at 2.17 GHz with substrate dimensions of 0.29λo × 0.29λo × 0.01λo. Percentage input impedance bandwidth (S11 < −6 dB) is 13.4% for first and 19.4% for second band, respectively. The proposed antenna shows monopole-like radiation pattern in xz-plane while dipolar-type in yz-plane at both frequencies of operation, respectively. The measured gain of proposed antenna is 1.8 and 1.6 dB at 1.72 and 2.17 GHz with radiation efficiency of 97.2 and 99.1%, respectively. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1444-1447, 2015 [ABSTRACT FROM AUTHOR]

A worst-case estimate of an envelope correlation coefficient (ECC) is obtained for small multiple-input multiple-output (MIMO) mobile antennas operating below 1 GHz. The worst-case estimate is numerically derived in this paper using spherical and exponential wave functions. The derived result confirms that the worst-case ECC can be easily obtained from the rotation angle between the radiation patterns of two MIMO elements, which are attained directly from the amplitude of 2D electric field patterns without any additional phase and polarization information. As a practical example, MIMO mobile antennas with different antenna element arrangements are compared to verify the validity of the proposed worst-case estimate. Moreover, based on these analyses, we also suggest an effective approach to reduce the ECC of a small MIMO mobile antenna operating below 1 GHz by properly locating the antenna elements to make the radiation patterns perpendicular to each other. [ABSTRACT FROM AUTHOR]

ABSTRACT In this paper, an efficiency enhancement technique is proposed for a loop type ground radiation antenna on a small sized ground plane whose resonance frequency of the fundamental ground mode is significantly higher than the operating frequency. The efficiency is enhanced by matching the resonance frequency of the ground mode with the operating frequency. This was accomplished with a structure consisting of a loop of wire and inductors installed at both edges of the rectangular ground plane. The total length of each fabricated wire is 80 mm, which can be easily accommodated in the rim of a mobile device. The technique also increased the operating bandwidth. The measured efficiency of the antenna using the proposed technique is 47.44% and the bandwidth is 74 MHz at the Z-wave band. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:476-478, 2017 [ABSTRACT FROM AUTHOR]

ABSTRACT In this article, a reconfigurable antenna that uses a PIN diode is proposed and experimentally investigated. The proposed antenna operates in planar inverted-F antenna (PIFA) and loop modes, which are controlled by the on/off operation of a PIN diode inserted into the radiating element. A supplementary stub line generates the additional resonance required to cover the GSM 850/900 bands. Geometrically, the proposed antenna is designed with a folded pattern for reducing its size and occupies an area of 7 × 50 × 4.8 mm3. The antenna operates in the hepta-band containing GSM850, GSM900, DCS, PCS, UMTS, LTE2300, and LTE2500, with a return loss lower than 6 dB. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2034-2037, 2014 [ABSTRACT FROM AUTHOR]

Multi-antenna design in compact mobile handsets at frequency bands below 1 GHz is very challenging, since severe mutual coupling is commonly induced by simultaneous excitation of the chassis' fundamental dipole mode by more than one antenna element. To address this problem, a novel multi-antenna design approach is proposed herein to obtain efficient and uncorrelated antennas. By manipulating the chassis structure, more than one characteristic mode is enabled to resonate at frequencies below 1 GHz. With proper excitations for different characteristic modes, which are orthogonal to each other, well matched multi-antennas with low coupling and correlation are achieved. A chassis loaded with two T-shaped metal strips above its longer edges is taken as an example modification to illustrate the effectiveness of the proposed design approach at 900 MHz. This modification creates a new characteristic mode which resonates near 900 MHz. Afterward, two antenna feeds were designed to efficiently excite the chassis' fundamental dipole mode and the T-strip mode with very low correlation. The T-strip antenna covers LTE Band 8 (880–960 MHz), and the dipole mode antenna covers both LTE Band 5 (824–894 MHz) and LTE Band 8. The proposed dual-antenna design was found to outperform a reference design significantly, both with and without user interactions (i.e., one-hand and two-hand data grips). Practical aspects of mobile handset antennas are also investigated. The prototype was also fabricated and measured, and the measured results show reasonable agreements with the simulated results. [ABSTRACT FROM PUBLISHER]

ABSTRACT A very compact multiband internal antenna for handsets and tablets is presented. The proposed antenna is targeted to cover popular noncellular applications including GNSS, WiFi (IEEE 802.11a/b/g), and WiMax (Bands 3A/4/5). This work examines a new ceramic material suitable for the internal antenna design which gives a shorter guided wavelength and multiple resonances to achieve antenna size reduction, sufficient space utilization, and bandwidth increase. The occupied volume of the antenna radiator is only 12 × 4 × 3 mm3, approximately equal to 0.06λm × 0.02λm × 0.016λm (λm is the longest wavelength of the applications) so the antenna can be placed in the device flexibly. The proposed antenna should be the smallest antenna covering GNSS-WiFi-WiMax ever reported. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:169-175, 2014 [ABSTRACT FROM AUTHOR]

A compact multiband internal antenna covering LTE/GSM/GPS/DCS/PCS/UMTS bands (748-960and 1575.42-2690 MHz) is presented for mobile terminals. The antenna combines a coupled-fed scheme and a magneto-dielectric material, which has low loss properties (magnetic loss tangent<0.08 ) up to 3 GHz, thereby achieving not only reduced antenna size but also improved bandwidth. In addition, a T-shaped monopole feeding line generating parasitic capacitance is applied to the proposed antenna. It plays an important role to shift the resonances, especially in the low band. The overall size of the antenna is only 35 × 15 × 4mm3, corresponding to0.0875×λ0 × 0.0375λ0 × 0.01λ0(λ0 is the wavelength at 750 MHz). The design process and the measured results of the proposed antenna are presented in detail. [ABSTRACT FROM AUTHOR]