inverted-F Antenna Research Articles

Hepta-Band Metal-Frame Antenna for LTE/WWAN Full-Screen Smartphone

In this letter, a metal-frame mobile antenna for Long-Term Evolution (LTE)/wireless wide area network (WWAN) smartphone application using a novel matching network is proposed. The proposed antenna consists of two parts, a typical inverted-F antenna for the low band, and an asymmetric T-slot for the high band. By means of multibranch technology based on matching circuit, the proposed design occupies a small part of the space surrounding the ground with only 1 mm ground clearance, which makes it a very competitive solution for full-screen phones. Finally, it completes the LTE 824–960 MHz and 1710–2690 MHz. The designed procedure and working mechanism of the antenna are discussed in detail. A prototype of the proposed antenna is fabricated and measured, and both simulated and experimental results are presented and discussed.

On-Line Partial Discharge Monitoring System for Power Transformers Based on the Simultaneous Detection of High Frequency, Ultra-High Frequency, and Acoustic Emission Signals

The article presents a novel on-line partial discharge (PD) monitoring system for power transformers, whose functioning is based on the simultaneous use of three unconventional methods of PD detection: high-frequency (HF), ultra-high frequency (UHF), and acoustic emission (AE). It is the first monitoring system equipped in an active dielectric window (ADW), which is a combined ultrasonic and electromagnetic PD sensor. The article discusses in detail the process of designing and building individual modules of hardware and software layers of the system, wherein the most attention was paid to the PD sensors, i.e., meandered planar inverted-F antenna (MPIFA), high-frequency current transformer (HFCT), and active dielectric window with ultrasonic transducer, which were optimized for detection of PDs occurring in oil-paper insulation. The prototype of the hybrid monitoring system was first checked on a 330 MVA large power transformer during the induced voltage test with partial discharge measurement (IVPD). Next, it was installed on a 31.5 MVA substation power transformer and integrated according to the standard IEC 61850 with SCADA (Supervisory Control and Data Acquisition) system registering voltage, active power, and oil temperature of the monitored unit. The obtained results showed high sensitivity of the manufactured PD sensors as well as the advantages of the simultaneous use of three techniques of PD detection and the possibility of discharge parameter correlation with other power transformer parameters.

Small‐size four‐element antenna system for 2 × 2 LTE LB and 4 × 4 LTE M/HB MIMO operations in5Gmobile terminals

A small-size four-element antenna system for 2 × 2 LTE low band (LB, 698-960 MHz) and 4 × 4 LTE middle/high band (M/HB, 1710-2690 MHz) multiple-input multiple-output (MIMO) operations in 5G (fifth-generation) mobile terminals is presented. The proposed antenna system is formed by two identical tunable loop antennas and two identical coupled-fed IFA (Inverted-F Antenna) antennas. By loading a RF switch with four output states as tunable component, the proposed loop antenna can not only operate in the M/HB, but also achieve improved bandwidth coverage in the LB. Each coupled-fed IFA element operating in the M/HB with compact volume. The four antennas are placed on the both short side-edge of the mobile terminal with small ground clearance of 4.2 mm. The simulated S-parameters show that the proposed MIMO system can cover 698 to 960 MHz and 1710 to 2690 MHz with reflection coefficients less than −6 dB and isolations are all more than 12 dB. Good MIMO performances such as radiation efficiencies, envelope correlation coefficient (less than 0.4 within the entire operation bands) and channel capacity are also obtained. The effects of user's hand(s) on performances for the proposed antenna system are also discussed. This four-element antenna system prototype is fabricated and measured.

Permittivity-Customizable Ceramic-Doped Silicone Substrates Shaped With 3-D-Printed Molds to Design Flexible and Conformal Antennas

3-D-Printing in antenna design is a recent research branch which is attracting academic and industrial interest. Nevertheless, despite the advantages in terms of antenna customizability, common filaments exhibit limitations in some contexts where platform tolerability, flexibility, and compactness are simultaneously required. Indeed, other than a rather low permittivity of commercial 3-D-printable materials, when flexibility is required, also significant loss tangent values must be accounted. To address this problem, a method to realize conformable flexible low-loss substrates with increased and customizable permittivity is proposed in this communication. It is based on the synthesis of ceramic-doped silicone structures shaped through 3-D-printed molds by using alumina and barium titanate as ceramic filler. Different substrates were firstly realized and characterized in terms of permittivity and loss tangent at different doping percentages. Then, a first validation on 2.4 GHz conformal patch antennas exploiting both third dimension and increased permittivity is presented. Finally, a wearable and compact bracelet-shaped UHF RFID planar inverted-F antenna (PIFA)-inspired flexible antenna is designed, tested when applied on the human body, and compared with a previously realized version 3-D-printed in polylactic acid. In spite of comparable performance, the novel device exhibits considerable size reduction and improved wearability, thus confirming the effectiveness of the proposed approach.

A planar inverted-F antenna-based chemical sensor for ion concentrations

The development of new wireless sensing devices could provide significant opportunities for medical and environmental applications. A planar inverted-F antenna (PIFA) is a typical antenna that is widely used in communications. Here, we report here a PIFA for chemical sensing of ion concentrations. When the ion concentration increases, the reflection coefficient of the antenna decreases accordingly. The PIFA sensor shows a linear detection range from 0.15 μM to 15 μM. We expect that this study could offer exciting opportunities for fundamental studies as well as applications of wireless antennas for chemical and biological sensing, and advance related healthcare and environmental applications.

Isolation enhanced MIMO PIFA system with multiple reconfiguration techniques

In this study, a reconfigurable, two-element, multiple-input multiple-output (MIMO) printed inverted-F antenna (PIFA) is presented with an enhanced isolation ability. The MIMO antenna system is designed using three different reconfiguration techniques that are based on positive-intrinsic-negative diodes, radio frequency micro-electromechanical switches and varactors. Their impact on the performance of the PIFA and the MIMO system is evaluated in terms of radiation characteristics, gain, power dissipated, radiation efficiency, linearity, biasing requirements and MIMO performance. Isolation between the two MIMO antenna elements is enhanced by integrating a reconfigurable band-reject filter within the ground plane between the radiating elements. The band-reject filter is reconfigured simultaneously with the radiating elements, hence resulting in less coupling and better isolation. The MIMO system along its various components is fabricated for the three different reconfiguration techniques and the comparison with predicted data shows great agreement.

A compact wideband circularly polarized quadrifilar antenna with PIFA elements for UHF RFID readers

AbstractIn this paper, a compact circularly polarized quadrifilar antenna with planar inverted-F antenna (PIFA) elements is presented. The proposed antenna consists of four PIFA elements and a Wilkinson divider-based feed network fabricated on FR-4 substrate (ɛr = 4.4, loss tangent = 0.02, thickness = 1.6 mm). The total size of the antenna is 120 × 120 × 13.2 mm3. Impedance matching with a reflection coefficient <−15 dB and an axial ratio (AR) <3 dB are achieved over the global ultra-high frequency (UHF) radio frequency identification (RFID) frequency band and beyond. The realized gain ranges from 2.25 to 3.75 dBic within the frequency band of interest from 860 to 960 MHz with a directional radiation pattern. The proposed antenna is compact, low-cost and extremely wideband in terms of matching and AR compared to state-of-the-art UHF RFID reader antennas.

Design and Development of a Tunable Ferroelectric Microwave Surface Mounted Device.

Based on a Ba(1-x)SrxTiO3 ferroelectric thin film, a discrete tunable surface mounted device (SMD) capacitor has been developed for microwave frequency applications. The proposed SMD topology has the particular advantage of inherent decoupling between the RF signal and the dc biasing voltage, necessary to tune the ferroelectric permittivity. The design and technological development of the SMD component is presented, and the synthesis of the ferroelectric thin film is summarized. Material characterization shows convenient tunability, while low dielectric losses at 10 MHz. The integration of the SMD tunable capacitor into a Planar Inverted-F Antenna has been done in order to evaluate the agility and tunability performance of the antenna.

Compact reconfigurable PIFA antenna for wireless applications

This paper presents, new compact and multiband frequency reconfigurable planar inverted-F antenna (PIFA). The antenna is designed and optimized to cover mobile application devices like GPS, WLAN/Wi-Fi, WiMAX, 4G LTE, UWB, and satellite applications. The frequency reconfigurability is obtained by using only a single RF switch (PIN diode) for changing the operating frequency. The antenna dimensions are 45.6x39.6x1.6 mm 3 printed on an FR-4 epoxy substrate with relative dielectric constant er = 4.3, loss tangent tan (δ) = 0.002 and 50 Ω coaxial feed line. The proposed antenna has two patches connected by a single PIN diode. The antenna introduces nine resonant frequencies under (S11 ≤ -10 dB) which are: 0.980 GHz, 3.392 GHz, 3.924 GHz, 4.554 GHz, 5.82 GHz, 6.81 GHz, 7.305 GHz, 8 GHz and 8.105 GHz in the ON and OFF states of the PIN diode which are applicable to cover GSM900, WLAN/Wi-Fi, WiMAX, 4G LTE, UWB, and satellite systems. The obtained maximum simulated gain is 8.45 dB at 6.81 GHz. The lowest return loss is obtained to be -42 dB at 5.854 GHz. Detailed simulation and measurement results are explored and studied in this research. The CST software is used to simulate and optimize the proposed PIFA antenna. The proposed antenna has been fabricated and produced a good agreement with the simulation results.

Integrated planar inverted-F antenna on laptop computer’s hinge for 2.4/5.2/5.8-GHz WLAN operation

ABSTRACTA compact planar inverted-F antenna (PIFA) placed on one of the two hinges of a laptop computer is proposed for wireless local-area network (WLAN) operation. The aim of this design is to integrate the PIFA’s metal surroundings as part of the radiating structure. When the PIFA is fed, resonant modes in the hinge slot bounded by the two hinges, display ground plane, and keyboard ground plane can in turn be excited. Since the 200 × 5 mm2 slot is much larger than the 10 × 5 mm2 PIFA itself, the latter, although compact and structurally simple, can be made efficiently radiating with the help of the former. Measured efficiencies are all over 50% in the desired three WLAN bands

A Low-Profile Wideband PIFA Based on Radiation of Multiresonant Modes

In this letter, a low-profile and wideband planar inverted-F antenna (PIFA) based on multiresonant modes is proposed for wireless local area networks and the Internet of Vehicles applications. Through cutting a rectangular slot at the zero-current position of the TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3/2,0</sub> mode, a resonant slot mode (TMRS) is excited. Meanwhile, to enhance the impedance bandwidth (IBW), the frequency of TMRS (fRS) is decreased to close to the frequency of TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3/2,0</sub> (f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3/2,0</sub> ) by enlarging the length of the rectangular slot. To further enhance the IBW, the frequency of TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2,2</sub> (f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2,2</sub> ) is increased with little change on that of TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3/2,0</sub> and TMRS modes by reducing the length of the rectangular patch. Moreover, capacitive coupled feed is used by loading a small rectangular strip (SRS) on the top of the feeding probe connected with the bottom of the substrate and the ground plane, and the impedance can be matched through adjusting the size of the SRS. To verify the predicted results, the proposed low-profile wideband PIFA is fabricated and measured. The measured results show that the IBW of the proposed PIFA is enhanced to about 33.33% (from 5 to 7 GHz) at the profile of 0.036λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> by combining three resonant modes, and it is 7.41 times of 4.5% of the traditional PIFA.

A Planar Inverted-F Antenna (PIFA) Loaded with Slot for RF Energy Harvesting Application

A Planar inverted-F Antenna (PIFA) with minimum height and enhanced gain is designed for RF energy harvesting applications. The proposed PIFA operates in the frequency range from 920 to 960 MHz with S11<-10 dB bandwidth of 40MHz. The antenna is designed with a copper sheet of thickness 0.1 mm and is placed at a height of 6.9 mm from the ground plane. Air medium and FR4 epoxy material are used as dielectric substrate. In order to miniaturize the size of PIFA, a rectangular slot of size 2×2 mm2 is etched in the radiating patch. In the proposed design, this feature is made unique from the similar type of antenna reported in the literature. The introduced rectangular slot not only provides miniaturization but also removes the requirement of an external impedance matching circuit. A ground plane via shorting pin at the height of 6.9 mm from the radiating patch is included in the design to enhance the gain of the PIFA antenna. The measured results show that the proposed PIFA yields a return loss of -12 dB at the resonating frequency of 947 MHz, with measured realized gain and total efficiency of about 2.71 dBi and 87.5% respectively.

Dual‐band frequency‐reconfigurable MIMO PIFA for LTE applications in mobile hand‐held devices

In this study, dual-port dual-frequency tuneable MIMO planar inverted-F antenna (PIFA) is presented for mobile handheld device applications. The proposed MIMO antenna consists of two symmetrical PIFAs with the centre-to-centre distance of 43.0 mm (0.1906λ 0 ). The dual-band tunability is achieved by changing the capacitance (V 1 and V 2 ) of 4.15 pF (0 V)-0.72 pF (15 V). The impedance bandwidth of -6 dB is realised from 0.8 to 0.98 GHz for the lower band and 1.65 to 2.2 GHz for the higher band. The proposed antenna provides the independent frequency tunability without disturbing the frequency bands. It shows the good isolation for both the tuneable bands >20 dB without using any coupling element between the antenna structure. It has a peak realised gain of 3.44 dBi, good efficiency of > 75% and envelope correlation coefficient of 0.007. In addition, the proposed PIFA performance is analysed with total active reflection coefficient, channel capacity, diversity gain, multiplexing efficiency, mean effective gain and specific absorption ratio for the tuneable range of frequencies. The good agreement is obtained between simulation and experimental performances to validate the antenna parameters.

Miniaturized PIFA for 5G Communication Networks

This paper designed a miniaturized Planar Inverted-F Antenna for 5G communication networks, including Long-Term Evolution Advanced mobile communication services. By showing the radiation pattern, voltage standing wave ratio, and antenna gain of the designed Planar Inverted-F Antenna, this paper evaluates its performance. To show the key characteristics of the Planar Inverted-F Antenna, this paper modeled and simulated it with various variances. Moreover, the real Planar Inverted-F Antenna was fabricated and measurements were done to validate the simulated characteristics of the internal antenna.

Design and on-body evaluations of a low-cost wearable PIFA for on-body applications

A flexible low profile textile antenna based on planar inverted-F antenna (PIFA) structure is presented in this paper. This topology has been chosen due to its design simplicity, relatively large bandwidth and the existence of a full rear ground plane, which shields against the effects of the body. The antenna topology which is designed on a 4 mm-thick felt substrate is presented. Conductive textile (Aaronia-shield) is applied as the antenna’s radiator and ground plane due to its light weight, low surface resistance and good conductivity. The antenna performance in free space and bent conditions in the proximity of human body are studied, followed by a numerical investigation on the influence of relative humidity on the textile antenna performance. The fabricated PIFA is assessed experimentally and is found to be in good agreements with the simulation results. Finally, the antenna is attached to a compact RF module and is evaluated on body in a practical environment. The wireless link quality is also evaluated in an indoor laboratory environment.

Design Implantable Antennas with Human Body Effect

Implantable antenna devices have made great progress for healthcare services. Amongst the overall components of the implantable device, the antenna is the most important component that exists; it used to transmit the biological data wirelessly from inside the human body tissues to an external receiver. However, the human body tissues’ surrounding the antenna decrease the performance of the radiation antenna device, change its characteristics and absorbs most of its radiation. It also limits the size of the implantable device and its battery. Therefore, the design of the implanted antenna inside the human body requires many challenges while meeting many contradictory design parameters at the same time. Therefore, in this research, we mainly focused our spotlight on investigating and designing new antenna structures with robust performance against the human body tissue effect. In this research work, we presented two designs of a dual-band microstrip patch implantable antenna to operate ((401-406 MHz) Medical Device Radio-Communications (MedRadio), 433MHZ 2.45 GHz Industrial, Scientific and Medical (ISM) bands, respectively. This is to satisfy the requirements of data transfer, power saving and wireless power transfer. The first design in this paper is a new shape of microstrip patch implantable antennas with meandered serpentine slot, with a single feed point. This shape of design allows us to increase the length of the current path in order to decrease the antenna size and covers MICS and ISM bands with new dimensions of (31 x 25 x 1.63) mm, the measured frequencies range we obtained it’s from 378MHz to 450 MHz (17.3%) at the lower band and from 2.46 to 2.68 GHz (8.56%) at the upper band for 11 less than -10 dB. The second simulated design is a compact dual-band Planar Inverted-F Antenna (PIFA) with Open-End Slots on ground with dimensions of (19.8x19.4x1.27) mm the measured frequencies from 325MHz to 407MHzrange at the lower band and from 2.412GHz to 2.482GHz for PIFA antenna, the designs of both antennae constructed and measured using CST and HFSS simulation and measurement setup. We also explained and demonstrated the performance of these antenna designs and the effect of human body tissue on antenna parameters, based on the reflection coefficient in normal and bent conditions.

Dual band frequency tunable planar inverted‐F antenna for mobile handheld devices

A single feed, dual-band frequency tunable planar inverted-F antenna (PIFA) is presented for mobile handheld device applications. The proposed antenna is designed using the transmission line model. The dual-band frequency tunability is achieved by varying the capacitance of the varactor diode between 4.15 pF (0 V) and 0.72 pF (15 V). The measured impedance bandwidth of −6 dB is realized from 0.8 to 0.98 GHz for the lower band and 1.65 to 2.2 GHz for the higher band. The designed antenna provides the independent frequency tunability for both the bands without disturbing each other. The maximum antenna gain is estimated 2.64 dBi for the proposed PIFA. Also, it has a maximum efficiency of ~85% for the mobile handheld device. In addition, the proposed PIFA is investigated with SAM phantom model for head and hand, found to be within the acceptable SAR limit of 1.6 W/Kg.

DTC-Enabled Frequency-Tunable Inverted-F Antenna for IoT Applications

In this letter, an integrated frequency-tunable inverted-F antenna is presented. Thanks to a reconfigurable circuit using a digitally tunable capacitor (DTC), the antenna resonant frequency can be shifted over 32 different positions from 600 to 960 MHz. This tunability is used to compensate the frequency detuning caused by the change in the antenna close surrounding. The small dimensions as well as the digital control and the low power consumption of the reconfiguration circuit make the proposed antenna a good candidate for Internet of Things applications.

Design of Combined Printed Helical Spiral Antenna and Helical Inverted-F Antenna for Unmanned Aerial Vehicle Application

The design and implementation of printed helical spiral antenna (PHSA) and helical printed inverted-F antenna (IFA) are presented for unmanned aerial vehicle (UAV) with global positioning system (GPS) $L1$ band (1.57 GHz) and telemetry communication frequency band (2.33 GHz) applications. The proposed antenna is miniaturized by co-winding the radiation elements on the same ceramic rod, surface covering by dielectric sealant, inserting a high permittivity dielectric load into the helical structure, turning and meandering the radiation element of PHSA into a spiral parallelogram structure. The PHSA and helical IFA antenna radiation elements are manufactured by silver pasted on the same hollow ceramic cylinder with a diameter of 12 mm and a height of 24.7 mm. The experimental and simulation results show that the proposed PHSA and IFA can achieve the gain of 0.05dB and 1.97 dB respectively and be suitable for GPS $L1$ band and telemetry communication frequency band (2.33 GHz) applications separately.

Isolated Ground-Radiation Antenna With Inherent Decoupling Effect and its Applications in 5G MIMO Antenna Array

This paper studies an isolated ground-radiation antenna (iGradiANT) that has inherent isolation with another closely-located antenna element and demonstrates its applications in 5G multiple-input multiple-output (MIMO) antenna array. The proposed iGradiANT is accomplished by merely employing a small out-of-ground loop into a traditional ground-radiation antenna (GradiANT). Hence, in contrast to the traditional GradiANT, the proposed iGradiANT can simultaneously support an in-ground loop-type current mode and an out-of-ground loop-type current mode, responsible for far-field radiation and near-field energy cancellation, respectively. In this way, the proposed iGradiANT can exhibit an intrinsic decoupling effect with the adjacent antenna element. Hereby, a typically used inverted-F antenna (IFA) and a normal loop antenna are adopted to separately validate the functionality and versatility of the proposed iGradiANT in establishing $2\times 2$ MIMO antenna sets without any separation. Furthermore, an $8\times 8$ MIMO antenna array is demonstrated for the usage of 5G terminal devices; both simulation and measurement are conducted to verify its radiation performance and diversity performance.