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In this study, a flexible multiband fractal antenna mimicking dendrite structure is proposed and designed by combining bionics and fractal theory. The dendritic structure of neurons is extracted and simplified into a simple and clear geometric structure. The initial antenna model is obtained by fractal operation on the geometric structure, and finally, four effective bands are obtained. The antenna is printed on a 50 ∗ 70 ∗ 0.1 mm3 polyimide dielectric board and fed by a coplanar waveguide. This paper discusses the effect of the human body on the performance of the antenna and the robustness of the antenna in the bending regime. The gain, efficiency, and cross-polarization of the antenna were tested using a microwave anechoic chamber. The measured antenna covers 1.37 GHz-1.93 GHz (relative bandwidth 35%), 2.25 GHz-2.51 GHz (relative bandwidth 10.7%), 3.13 GHz-3.81 GHz (relative bandwidth 19.3%), and 4.46 GHz-5.5 GHz (relative bandwidth 21.1%) four operating frequency bands. The maximum gain is 6.05 dBi and the maximum efficiency is 91.05%. The antenna can be used for Bluetooth WLAN (Wireless Local Area Network), 4G (4th Generation Communication System), 5G (5th Generation Mobile Communication System), WiMAX (Worldwide Interoperability for Microwave Access), etc. The test results are in good agreement with the simulation results, which proves that the antenna can meet various wireless communication requirements. [ABSTRACT FROM AUTHOR]

In this paper, a novel switchable bandpass filter is proposed. By switching p-i-n diodes on/off, the proposed filter can be switched between the single-band bandpass filter and the dual-band bandpass filter. The filter is mainly composed of eight pairs of series LC resonators, which generate passbands and transmission zeros. Considering the requirement of miniaturization and low cost, the filter is realized by interdigital capacitors and microstrip section inductors. The layout is designed by 3D simulation software HFSS, and the active part is designed by ADS software. The proposed filter has a compact structure, and its size is only 22.20 mm × 25.66 m m. For a demonstration, a switchable bandpass filter has been designed, fabricated, and measured. The simulated and measured results have a good agreement. [ABSTRACT FROM AUTHOR]

Based on the simplicity of the design method, this paper presents a new approach for developing matched subbands when splitting two mismatched dual-wideband bandpass filters (BPFs) for the fifth generation (5G), wireless access systems (WAS), wireless fidelity (Wi-Fi), worldwide interoperability for microwave access (WiMAX), wireless local area network (WLAN), radar, and other communication devices. The method's novelty involves using identical quarter-wavelength resonators terminated by alternated short-and-open stub configurations. Both configurations alternate and describe a perfect symmetry by their location from each other to make the subbands possible in the low-frequency and its harmonic (high-frequency) bandwidths (BW). A stub admittance Y 1 is defined and associated with the mainline section characteristic impedance Z 0 and an operating frequency f 0 . A quality factor Q a p is connected to Y 1 and f 0 to approach the BPF global quality factor Q g initially fixed. The stub characteristic impedance and the mainline one differ, while electric lengths (stub and mainline section) are identical. Using the operating frequency determines physical dimensions, creates harmonic frequencies and the rejected BW, mismatches the main frequency BW, matches the subbands, and creates transmission zero (TZ). Hence, a 28.118-dB stopband that separates the two bandpasses at 9.373 GHz is made. At the same time, the unmatched dual ultrawideband (UWB) covers a large panel of communication systems. The lowest (3.146–5.431) and highest (11.891–14.749) GHz BW exhibit a minimum insertion loss (IL) of 0.656 dB and 3.027 dB. The subbands return losses (RL) are better than 28 dB and 19 dB, respectively, and a flat group delay of 0.205 ns is obtained in the upper band. All subbands adaptation methodology is read from 10 dB of the RL. In that case, the four matched subbands in its lower wideband are 3.327–3.709 GHz and 4.442–5.048 GHz, and in its higher wideband are 11.922–12.486 GHz and 14.281–14.653 GHz. The 2275/2858 MHz is the dual-wideband with a fractional BW 53.282/21.456%. The fabricated prototype has validated the EM-simulations, and Anritsu MS4642B 20 GHz vector network analyzer (VNA) has been used for experimental results by scanning the frequency range 3 GHz–15 GHz. The tested prototype is made with a 1 mm FR4 HTG-175 thickness by considering a dielectric constant of 4.4, and its overall size occupies 22.45 × 5.72 m m 2 (0.32 λ 0 × 0.082 λ 0 mm 2 ). [ABSTRACT FROM AUTHOR]

This paper incorporates the structural characteristics of chrysanthemums in nature and fractal geometry theory into the antenna structure design and a novel-structured fractal multiband fractal microstrip antenna with a chrysanthemum petal structure is proposed. The antenna can cover commercial frequency bands from the second to fourth generation (4G), satellite navigation, wireless local area networks, and Bluetooth. The antenna radiator imitates the structure of chrysanthemum's petals in nature, and a basic arc shape is iterated many times according to a certain proportional coefficient. After simulation and comparison, the second iteration can achieve the best antenna performance, and the antenna adopted the coplanar waveguide feeding method to broaden the antenna bandwidth. The antenna covers three effective frequency bands of 1.58–2.68 GHz (64.7%), 2.76–4.01 GHz (33.9%), and 4.68–5.35 GHz (13.4%). The antenna dielectric board is made of FR-4 material, the dielectric constant is 4.4, and the actual size is 41 × 29 × 1.6 mm3. The antenna performs fractal iteration at a small size, and the approximate calculation of the frequency band is completed by comparing the ratio of each ring to the current vector diagram. The design of the antenna is to use HFSS for antenna modeling and parameter optimization, and the model under different conditions were compared and analyzed. By comparing the test results of the antenna prototype with the simulation structure in the electromagnetic anechoic chamber, the rationality of the antenna is verified. [ABSTRACT FROM AUTHOR]

In this article, compact inverted F‐antennas (IFAs) operating in the 3.5 GHz band is proposed for future 5G smartphone applications. The conventional IFA is modified to make the structure compact and efficient. The additional IFAs are aligned in face‐to‐face configuration to reduce the coupling between them up to some extent. Furthermore, a novel decoupling element is incorporated between antenna pairs to effectively enhance the isolation. As a result, the proposed building block exhibits isolation higher than 28.2 dB between two adjacent ports. Based on highly isolated building blocks, a 4 × 4 and 8 × 8 multi‐input multi‐output (MIMO) antenna array is designed and investigated which is operated in 3.5 GHz (LTE band 42). The proposed 8 × 8 MIMO antenna array has four compact building blocks and reserves sufficient space for integrating other antennas such as 2G/3G/4G antennas. To validate the simulated results, a prototype of the proposed antenna is fabricated and tested. Over the entire operating frequency, the fabricated 8 × 8 MIMO antenna array obtain high isolation of more than 27.3 dB, and high antenna efficiency (>61%). Also, its corresponding measured envelope correlation coefficients are lower than 0.04 and channel capacity was about 39.1–40.6 bps/Hz. The measured results show that the proposed MIMO antenna array is a good candidate for future fifth‐generation smartphone applications. [ABSTRACT FROM AUTHOR]

This work proposes a single port hexagonal slotted rectenna operating at 2.45 GHz Wi‐Fi bands, using a hexagonally slotted shape of microstrip radiator surface followed by a voltage rectifier circuit using Schottky diode. A symmetrically extended ground plane and rectangular slots help in obtaining the desired resonance characteristics with improved antenna bandwidth. Three different antenna designs have been compared and analyzed. Best gain and wide most bandwidth is seen in the newly designed rectangular and hexagonal slotted design having symmetrically extended ground plane. A RF capacitor and inductor based matching network has been designed to maximize the wireless power transmission at 2.45 GHz. This also helps to enhance the rectifier efficiency for various values of load resistance and input power. Furthermore, for maintaining the small size and ensuring least amount of energy loss, the rectifier's ground has been directly connected to the antenna's ground plane. The proposed design has been simulated in HFSS and ADS software, prototyped, and measured. It has been seen in the results that, the proposed radio frequency (RF) power receiving antenna is performing very well at 2.45 GHz with a wide bandwidth ranging from 1.25 to 2.63 GHz. The proposed rectenna is having a maximum efficiency of 62.4% at 2.45 GHz with an input power of 0 dBm. Furthermore, with variations in the load resistance across a wide range of values from 4 to 12 kΩ under a wide range of low input power, the rectenna maintains an efficient power conversion, which is found to be an important parameter when the ambient RF signal input to the antenna is weak. As a result, the rectenna may be adaptable to a variety of low‐power electronic circuits by harvesting RF energy at 2.45 GHz Wi‐Fi Band. Furthermore, the proposed antenna can also be used for wireless medical telemetry, satellite phone and Wi‐Fi applications used for the frequency band 1.45 GHz as well. [ABSTRACT FROM AUTHOR]

In this study, a compact reconfigurable dielectric resonator antenna (DRA) array is proposed to operate in the band IEEE 802.11 WLAN. The main goal of this design is to propose an array feeding topology to avoid radiated beam squinting due to frequency alteration and acquire some gain enhancement with miniaturized array size. For that, the parallel–series geometry is used to layout a microstrip feeder with four output ports on the front plane. Each output port coupled with a rectangular slot (RS) at the bottom plane, and a rectangular dielectric resonator (RDR) mounted above the RS. The frequency reconfigurability is attained by employing PIN diodes that are integrated with the four output ports to operate as switches. Moreover, an impedance equivalent circuit model of the proposed array is postulated for studying the resonance behavior to ensure the validity of the proposed design prior to simulation and fabrication. The prototype 64 × 18 mm2 achieves frequency agility in the range of 5.8 to 5.17 GHz. Also, the realized gain ranges from 12.2 to 10. 5 dBi. The array specifications make it a decent potential candidate to be used for WLAN wireless systems. [ABSTRACT FROM AUTHOR]

A highly efficient self‐isolated multiple‐input multiple‐output (MIMO) antenna system functioning in the n46 5G NR band (5.15–5.925 GHz) for smartphone implementation is discussed in this paper. The system is made up of two blocks of vertically printed antenna pairs, placed at the exact center of the side frames of the smartphone. Each block comprises of a self‐isolated antenna pair with two inverted L‐shaped radiators facing each other, a T‐shaped isolating element, and a U‐shaped structure placed at the back of the radiators, and is attached to the ground plane. A simple coaxial feeding structure is deployed to excite the L‐shaped radiators. The T‐shaped structure placed between the two radiators has a crucial role in minimizing the mutual coupling between the two radiators, and its arm serves as a radiator. The self‐isolated antenna pair functions from 5.10 to 5.98 GHz, covering the entire n46 band (5.15–5.925 GHz) with over −16.8 dB isolation in the complete operating bandwidth. The parametric investigation of some ideal parameters and the antenna pair evolution stages to obtain the final structure is examined for a superior understanding of the functioning of the proposed MIMO smartphone system. The proposed self‐decoupled antenna pair MIMO system operates with a very high radiation efficiency and gain in the complete operating bandwidth, with radiating efficiency, total efficiency, and peak gain greater than 92%, 85%, and 6 dB respectively. The lowest obtained envelope correlation coefficient (ECC) value is 0.025 between the two elements in the antenna pair, which is very low when compared with the ideal value of 0.5. Various other parameters like channel capacity loss (CCL), mean effective gain (MEG), total active reflection coefficient (TARC), and diversity gain (DG) of the proposed system are also calculated and examined with the experimental results to study the diversity performance of the proposed MIMO smartphone system. A prototype of the proposed 4‐port MIMO smartphone system is fabricated and various parameters are examined. The coherence between the measured and the experimental outcomes stipulates that the proposed system is a capable contender for application in the upcoming 5G handheld devices. [ABSTRACT FROM AUTHOR]

Radio frequency (RF) energy harvesting from freely available electromagnetic fields is a promising alternative for powering smart electronic devices. This article presents a compact and efficient rectenna for RF energy harvesting at an Industrial, Scientific, and Medical (ISM) band of 2.4 GHz. A compact microstrip antenna with opened‐end slots and a full ground plane is designed. Moreover, a Greinacher voltage doubler topology‐based rectifier was designed to sense small input power levels. The antenna and rectifier optimization were performed through the simulation software. The optimized prototypes were fabricated and measured individually and as well as an integrated system. Measured results were in good correlation with the simulations. A peak measured efficiency of 75% with a constant output voltage of 2.9 V was achieved for the proposed rectifier at a small input power of 10 dBm. Furthermore, for demonstration of the RF conversion efficiency and output voltage, the antenna was integrated with the rectifier of load resistance, which was later replaced by LED for WPT demonstration purposes. The demonstration verified that the proposed rectenna with achieved efficiency and sufficient output voltage is a promising candidate for powering smart electronic devices. [ABSTRACT FROM AUTHOR]

The realization of a compact dual band reconfigurable filtering antenna is described for WiMAX and WLAN application through this communication. First and foremost, a dual band filter is offered employing four open ended half wavelength Stepped Impedance Resonators (SIRs) to resonate at 3.2 GHz and 5.35 GHz. PIN diodes have been connected to the edges of the innermost resonators to switch the operation from dual passband to two different single passbands and to all stop configuration. Multipath coupling helps to create transmission zeroes on either side of passband enriching the selectivity. In order to implement the filtering antenna, a compact monopole antenna is presented using two triangular radiating patches radiating at 3.2 GHz and 5.35 GHz. Finally, the filter and the antenna structures are combined to accomplish the proposed dual band reconfigurable filtering antenna. The results with reference to return loss and radiation pattern are provided and good performances are obtained. The suggested filtering antenna has the reflection coefficient lower than −16 dB for all the desired operating bands. As well, it offers gain of about 3.21 dBi and 5.08 dBi at the two radiating bands. The developed prototype is fabricated and measured to examine the anticipated and simulated results where a close agreement is established between them. [ABSTRACT FROM AUTHOR]

Electromagnetic (EM) lens antenna designs using cascaded metasurfaces for gain enhancement and beam steering applications are proposed. Two different lens aperture designs are proposed and populated with aperiodic unit cells of size 0.2λo × 0.2λo. In lens Design 1, the unit cells of different phases are distributed in concentric circular zones, whereas in lens Design 2, the unit cells of different phases are distributed in vertical linear zones on the aperture of the EM lens. Both lenses are composed of two cascaded metasurfaces with an air gap of 0.047λo (where λo = 51.7 mm at 5.8 GHz). For gain enhancement, the metasurfaces are positioned at an optimum focal distance, f = 0.61λo above source patch antenna (f/D = 0.3). Beam steering is accomplished by phase transformation of the source antenna, which can be realized by mechanically sliding the passive metasurfaces in one direction (i.e., ±x‐direction) above the source antenna. The prototype of the two proposed lenses are fabricated and tested. The measured peak boresight gain obtained from Design 1 and 2 are 14.98 and 15.12 dBi, respectively. The experimental results show −25° to +25° and −27° to +27° beam steering range for Design 1 and 2, respectively, with a little gain degradation at other angles. [ABSTRACT FROM AUTHOR]

A novel planar pattern reconfigurable antenna is presented. The proposed antenna consists of four identical antenna elements distributed at different positions on a F4B255 substrate forming a cross shape. Each antenna element is composed of a direct fed magnetic dipole with bow tie shape and four coupling fed magnetic dipoles with rectangular shape which achieves wide bandwidth and titled radiation pattern. The ground plane under each antenna element is etched with taper shape to reduce the coupling among antenna elements. The four antenna elements are linked to and fed by one port via a step shaped metal strip on the ground plane and radiation layer, respectively. A PIN diode is mounted in each strip to switch the connection/disconnection of each antenna element with the feeding port. Pattern reconfiguration is obtained by electrically choosing the excitation of each antenna element. The proposed antenna operates in four states with four steerable beam directions of θ = ±45° in both xoz and yoz planes. The measured common bandwidth for the four states is 5.15–5.93 GHz and the measured gain ranges from 6.14 to 8.45 dBi for four states within the bandwidth. The proposed antenna has a low profile and wide bandwidth which makes it a good candidate of micro base station for IEEE 802.11ac Wireless Local Area Network (WLAN) (5.15–5.85 GHz) applications. [ABSTRACT FROM AUTHOR]

A miniaturized cavity‐backed antenna loaded with slots is designed using substrate integrated waveguide (SIW) technique for ISM/WiMAX/C‐band/RFID applications. This antenna has been developed by embedding slots onto a hexagonal cavity for quad band radiation. The proposed antenna possesses hexagonal cavity, inverted U‐shaped slot and innermost inverted U‐shaped slot, which are governed by an inset microstrip feedline. The hexagonal SIW cavity‐backed antenna offers cavity modes TM110 at 4.16 GHz and TM210 at 5.8 GHz. Two inverted U‐shaped slots are introduced on the top metallic surface of the cavity to drive the lower resonant modes for acquiring antenna miniaturization. These lower resonance frequencies are formed by hybrid mode (i.e. TM110+TM210) at 2.4 GHz and coupling of hybrid mode (i.e. TM110 + hybrid mode + TM210) at 3.33 GHz. The ANN optimization method has been performed to enhance the performance of the antenna using MATLAB. The designed antenna has a compact size of 25 × 25 × 1.6 mm3, which is fabricated on a low cost FR‐4 substrate having εr=4.4 and tanδ=0.002. To validate the simulated equivalence, the fabricated antenna has been measured. It yields a fractional bandwidth of 5.04% (2.31–2.43 GHz) in the hybrid mode at 2.38 GHz, 6% (3.22–3.42 GHz) in the coupling of hybrid mode at 3.33 GHz, 19.19% (3.97–4.78 GHz) in the cavity mode TM110 at 4.22 GHz and 7.2% (5.69–6.11 GHz) in the cavity mode TM210 at 5.8 GHz with stable radiation pattern. [ABSTRACT FROM AUTHOR]

A low profile printed dipole antenna (PDA) backed by broadband Giuseppe Peano fractal artificial magnetic conductor (AMC) is introduced for wireless communications. First, a suggested PDA with a pair of microstrip dipoles excited by an E‐shaped microstrip feedline is used to expand the bandwidth in the range of 5.96–7.04 GHz (S11 ≤ −10 dB). Then, the suggested Giuseppe Peano fractal AMC surface as a reflector of the antenna is inserted into the PDA to gain improved radiation efficiency. The PDA with the 6 × 6 Giuseppe Peano AMC array exhibits −10 dB measured impedance bandwidth of 4.95–7.05 GHz (35%) for wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) applications. The suggested PDA with AMC compared to the PDA without AMC exhibits a size reduction of 38%, enhanced gain up to 8.2 dBi, and excellent impedance matching (at least −20 dB) with directional radiation patterns. The novel AMC unit cell is realized based on the Giuseppe Peano fractal patch to operate at 6.10 GHz with an AMC bandwidth of 5.15–7.10 GHz (32%). Besides, by loading 12 × 12 AMC reflector into the four‐element array of PDA, low profile wideband structure with enhanced radiation properties are achieved. The measured results show the broad bandwidths of 5–7 GHz for all elements with enhanced gains and good isolations between the elements (more than 24 dB) for multiple‐input multiple‐output (MIMO) systems. [ABSTRACT FROM AUTHOR]

This paper proposes a dual‐band filtering patch antenna with out‐of‐band rejection for 5G applications. The design is based on the substrate integrated suspended line (SISL) platform, which combines a T‐junction power divider, a square driven patch with an I‐slot, and two parasitic strips, fed by slot coupling to achieve the desired performance. The working mechanism of dual‐band operation is explained by analyzing |S11| and electric field distribution. The slot on the G5 layer can generate two different resonance modes in the upper and lower frequency bands, and a radiation null is produced simultaneously. The driven patch and parasitic strips generate additional resonant modes, and two radiation nulls are generated, which improve the frequency selectivity. The realized antenna operates in two frequency bands: 3.38–3.6 and 4.73–5.23 GHz. The peak gain can reach 9.11 and 7.61 dBi in the higher and lower bands, respectively. The excellent performance of this antenna provides one more choice for 5G communication systems. [ABSTRACT FROM AUTHOR]

A compact dual‐polarized omnidirectional (DPO) antenna with dual‐band characteristic is presented in this article. The main structure of the antenna is a metal box, which is composed of a horizontally folded narrower slot on the three sides for vertical polarization and a vertically folded wider slot lying on other three sides for horizontal polarization. Two different coupling feedings inside the box are designed for the two slots so as to obtain good omnidirectional radiation properties in two frequency bands of 2.4 and 5.5 GHz. The proposed structure is only 30 mm × 30 mm × 10 mm in size (0.24λ0 × 0.24λ0 × 0.08λ0, λ0 stands for the wavelength of corresponding lowest operating frequency). A prototype has been built and measured. The measured results present the proposed dual‐band DPO antenna has two 10 dB return loss operating bandwidth of 3.7% (2.41–2.5 GHz) and 16% (5.05–5.93 GHz), with the isolation higher than 35 dB. [ABSTRACT FROM AUTHOR]

In this letter a novel notched multi‐input‐multi‐output (MIMO) flexible slot antenna with a C‐slot is proposed and designed for wireless body area network (WBAN) and Internet of Things (IoT) applications. The proposed antenna is comprised of four similar elements with the feed line of coplanar waveguide (CPW). Antenna is printed on flexible liquid crystal polymer (LCP) substrate with compact dimensions. The proposed UWB‐MIMO slot antenna can operate in range of 2.85–10.85 GHz with notched band from 4.9–6.425 GHz. The achieved notched band can filter the interference of WLAN (5.15–5.825 GHz), by adding an inverted orthogonal branch, great isolation is achieved, which is better than 24 dB over working bands. What's more, the parameters of diversity performance like gain, envelope correlation coefficient (ECC) and diversity gain (DG) are also analyzed. The actual measurement of bending test and the effect of human body indicates that the presented antenna is suitable for WBAN and IoT applications. [ABSTRACT FROM AUTHOR]

A low‐profile self‐hexplexing antenna based on the multimode substrate integrated waveguide (SIW) cavity is presented for mobile terminal applications. It has three feeding ports, each of which can generate two resonant modes. Taking the advantage of the truncated SIW resonant cavity, the footprint of the antenna remains compact in the multiple functional mode scenario. The proposed antenna operates at six different modes, namely TM10 mode at 3.55 GHz, TM01 mode at 4.85 GHz, TE110 mode at 2.45 GHz, TE220 mode at 5.6 GHz, TE110 mode at 3.4 GHz and TE120 mode at 5.35 GHz. Good agreement is achieved between the simulated and measured antenna performance. The excitation and field distribution of each mode is analyzed. Keeping the structure miniaturized, the proposed antenna realizes hex‐band characteristics without excessive feeding ports. It can be used for Microwave Access (WIMAX), the 5th Generation Mobile Communication Technology (5G) and Wireless Local Area Network (WLAN) applications, which is suitable for mobile handheld multiband terminals. [ABSTRACT FROM AUTHOR]

In this letter, a miniaturized high gain dual‐band circularly polarized antenna is proposed for the global satellite navigation system application. Centrosymmetric radiation structure with I‐shape branches helps improve the performance of the antenna in the low frequency within a limited area. The reflective phase modulation (RPM) surface with double zero‐reflection‐phase frequency points is analyzed and is used to lower the antenna profile. The bandwidth of the antenna is filtered assisted by the RPM surface. The composite left/ right hand transmission line is used in the feed network to balance the phase difference among the four feeding ports in the bandwidth. Simulation and measurement results show that the VSWR of the antenna is blow 1.5, the boresight AR is less than 3 dB, and the boresight gain is larger than 4.9 dBic in the double working band (1.164–1.279 GHz and 1.579–1.616 GHz). [ABSTRACT FROM AUTHOR]

In this paper, a low‐size and compact substrate integrated waveguide (SIW)‐based simultaneous transmit and receive antenna is developed for full‐duplex wearable telemetry applications. The antenna operates at 4.9 GHz (Wireless Local Area Network [WLAN]) and 5.8 GHz (Industrial, Scientific and Medical [ISM]) bands with acceptable gains. Keeping a proper gap between the two ports achieves an isolation of better than 29.8 dB. This antenna is kept compact (0.20 λg2, where λg is the wavelength at 4.9 GHz) by additional arc‐shaped slot in each radiator, which adds additional capacitance. The suggested antenna is simulated inside a 52 × 63 × 17 mm3 dummy wearable telemetry device and is worn on the subject's chest. Thanks to SIW technology, it has unidirectional radiation patterns, allowing a minimum beam towards the human body, and thus, offers lower specific absorption rate (SAR) at both frequency bands. The unique advantage is its capacity to receive and transmit the telemetry signals simultaneously. Its low profile, flexibility in the resonant bands, simultaneous transmission and reception, and lower SAR values make this antenna suitable for full‐duplex wearable telemetry devices. [ABSTRACT FROM AUTHOR]

A specific absorption rate (SAR) reduction approach is presented in this article, which is based on theories about electromagnetic properties and the boundary conditions of human tissue. The theory states that electric field components with different polarizations have different conditions for being absorbed by human tissue. A SAR reduction sticker made from a frequency selective surface (FSS) cell has been investigated in this article to reduce the energy absorbed by the human body from a mobile phone antenna. A dual‐band IFA with a wireless local area network (WLAN) band is also proposed as the reference antenna. The antenna's integration with the sticker makes there more hard‐absorbed components and less easy‐absorbed components before the electric field gets into the human tissue. Numerical simulations on SAR display a 16.7% and 42% decrease in the peak value of 10 g spatial‐average SAR at 2.4 and 5.5 GHz before and after the antenna was integrated with the sticker. The electric field has also been analyzed, showing great agreement with the theory. The analysis indicates that the proposed sticker would have a limited impact on the antenna's performance. The antenna and the sticker have been fabricated and measured, and the results agree well with the simulation. [ABSTRACT FROM AUTHOR]

In this article, a Super‐wideband (2.6–22 GHz) two‐elements multiple‐input‐multiple‐output antenna (MIMO) is presented with a dimension of 49 × 54.5 × 1.6 mm3 on an FR‐4 substrate. The antenna is also exhibited dual circular polarization (RHCP and LHCP) simultaneously at two separate ports at four frequencies of 5.2, 11.5, 14.66, and 16.75 GHz, which are extensively utilized for WLAN, X, and Ku‐band applications. Four EBG cells of various sizes have been installed across the feed line to maintain the antenna's efficiency and control the specific absorption rate (SAR). The antenna has a minimum isolation of 17 dB (20 dB for the important portion) in Super‐wideband (SWB) and excellent diversity performance. Simulated results of antenna‐like return loss, isolation, and diversity parameters have also been verified experimentally, which are in the acceptable range. Also, the calculated maximum SAR at 10 g is 1.095 W/kg with the head voxel model at 3.5 GHz. [ABSTRACT FROM AUTHOR]

A quad‐band bandpass filter is proposed using a defected microstrip structure (DMS) for GPS, WiFi, WLAN, and WiMAX applications. This filter uses a stub‐loaded stepped‐impedance resonator (SL‐SIR). The proposed filter is fabricated on an RT/Duroid5880 substrate (εr = 2.2, h = 0.787 mm, tanδ = 0.0009). Then, the LC equivalent circuit of the proposed filter is presented. A 28th‐order transfer function is obtained and approximated by 8th‐order transfer functions. The results of simulation, measurements and the LC equivalent circuit are in good agreement. The proposed filter operates at 1.6, 2.48, 3.76, and 5.44 GHz. The measured insertion losses are 0.32, 027, 0.51, and 0.41 dB in the four bands, while the return losses are better than 10 dB in all frequency bands. Finally, the proposed filter is compared with other bandpass filters. [ABSTRACT FROM AUTHOR]

This article proposes an additive manufacturing compact (30 × 36 × 0.125 mm3), flexible, and reconfigurable antenna with the ability to switch between wideband and dual‐band for wireless electronic devices used in the fifth generation (5G) systems and wireless local area network (WLAN) systems. The antenna consists of a folded branch line and an inverted L‐shape branch as radiator, and a slot on the ground plane. A vanadium dioxide (VO2) switch is screen‐printed on the folded branch line to reconfigure the operation frequencies. The antenna is optimized to operate for a wide bandwidth between 2.46 and 4.3 GHz when the VO2 switch is in the "OFF" state. The antenna exhibits dual narrow‐bands at frequencies of 2.4 and 5.2 GHz when the VO2 switch is heated up to 85°C or when a DC current of 50 mA is applied. Simulation and measurement show that the performance of the antenna remains relatively stable under different bending conditions in both the "ON" and "OFF" states of the switch. The operating frequencies can be independently controlled, and a guideline is discussed to design the antenna for other frequencies. [ABSTRACT FROM AUTHOR]

An optically transparent dual‐band antenna operates at Long Term Evolution (LTE), WiFi, Wireless Local Area Network (WLAN), and Vehicle to Everything (V2X) communications in the automotive environment. The proposed antenna is a coplanar waveguide fed pentagonal patch with a connected ground configuration. The antenna is developed on a soda‐lime glass coated with two layers of conductive oxides, viz. fluorine tin oxide (FTO) and indium tin oxide (ITO). The dual‐layer conductive oxide is chosen to reduce the sheet resistance to 4 Ω/sq thereby improving the antenna radiation properties. The proposed antenna has a footprint of 50 × 50 mm2. The prototype antenna is designed to operate at 1.5–3 GHz in the lower band and 4.3–7 GHz in the upper band with a percentage bandwidth of 61% and 47%, respectively. The prototype antenna is fabricated and the measured optical transmittance is greater than 72%. The antenna has measured peak gain of 0.6 and 2.7 dBi at lower and upper bands respectively. Furthermore, the on‐car performance of the antenna is estimated and presented using both simulation and measurement. The study inferred that the proposed antenna is suitable for deployment on the windshield of automobiles. [ABSTRACT FROM AUTHOR]

A compact CPW‐fed ultra‐wideband (UWB) multiple‐input–multiple‐output (MIMO) antenna with quad‐band‐notched characteristic is proposed in this work. The antenna elements are placed orthogonally, the introduction of defected ground structure (DGS) and double Y‐shaped stub makes the isolation between different antenna ports better than 20 dB, and the cutting of the excess dielectric substrate part reduces the antenna area by about 30.75%. Complementary split‐ring resonators and slots on the ground and the radiation patch have been introduced to achieve the four‐notch characteristics at 7 GHz lower digital microwave relay communicator band, 5.8 GHz upper WLAN, 5.25 GHz lower WLAN, and 3.5 GHz WiMAX. The wide bandwidth of the antenna is obtained by applying tapered feed line and CPW feed, which covers 2.88–12 GHz with the four‐notched bands of 3.34–3.93 GHz, 5.15–5.61 GHz, 5.72–6.0 GHz, and 6.75–7.6 GHz. Moreover, ECC (<0.02), DG (>9.99), the peak gain of 4.01 dB, good radiation pattern and TARC prove the presented antenna is suitable for UWB‐MIMO systems. [ABSTRACT FROM AUTHOR]

Wearable electronic devices are the basic components of wireless human body local area network. Due to their close contact with the human body, it is necessary to improve the flexibility and isolation of the antenna to maintain high signal transmission performance. In this paper, a flexible wearable antenna based on highly conductive graphene assembled film (GAF) and polydimethylsiloxane dielectric material is proposed. The planar combination of the powerful novel materials and supple polymer maximizes the flexibility and chemical stability of the antenna. In addition, the coplanar waveguide feeding and artificial magnetic conductor (AMC) structure enhance the efficiency and isolation with an easier preparation process. In the wearing measurement, the GAF antenna operates at 3.5 GHz for 5G communication frequency band and 5.8 GHz for ISM (Industrial, Scientific, Medical) frequency band. The GAF antenna has a minimizes SAR level, which in accordance with IEEE C95.1 International standard, by taking up a small space with 50.5 × 48.5 × 2.08 mm3. Furthermore, the GAF antenna has good radiation performance both under several different bending conditions and human body conditions. [ABSTRACT FROM AUTHOR]

A compact ultra‐wideband (UWB) printed monopole UWB with dual band‐notched characteristics has been designed and investigated in this manuscript. The Wi‐MAX and wireless local area network (WLAN) band rejection characteristics have been obtained by employing the circular ring and arc‐shaped slot along with rectangular slot in radiating patch. Overall size of proposed UWB antenna is 27 × 27 × 1.6 mm3, which consists of sprocket gear wheel shaped structure as a core radiating patch element and excited by using 50 Ω coplanar waveguide feed. The proposed antenna exhibits the UWB frequency spectrum from 3.1 to 10.6 GHz along with Bluetooth frequency range 2.4–2.48 GHz without disturbing overall dimensions of antenna. Proposed antenna reveals the measured VSWR operating bandwidth of 10.0 GHz in the frequency range from 2.0 to 12.0 GHz along with Wi‐MAX and WLAN rejected bands. Moreover, proposed antenna adorns the measured gain of −8.28 and − 9.98 dBi at rejected frequency bands, whereas, at other frequencies, it changes between 1.5 and 5.0 dBi. The radiation efficiency of proposed UWB antenna varies from 84% to 97% except rejected frequency bands. Group delay and radiation pattern have also been analyzed and found appropriate for the current UWB applications. Finally, the optimized structure of antenna with dual band rejection characteristics has been fabricated and tested for the authentication of simulated results. Both the results are compared and are found in good agreement with each other. [ABSTRACT FROM AUTHOR]

In this paper, an ultra‐wideband multiple‐input multiple‐output antenna with dual band‐notched characteristics is proposed. The radiating element is an octagonal structure using a tapered microstrip line to feed. A multimode resonator is introduced on one side of the microstrip feed line to achieve dual band‐notched characteristics, which eliminates the interference of wireless local area network band and X satellite communication frequency band. By using a diamond‐shaped defect ground structure and extending a parasitic branch at the centre axis of the ground, the mutual coupling of the antenna is reduced to −20 dB. The proposed antenna has a compact size of 30 × 35 × 0.8 mm3. The measured results are in good agreement with the simulation results. The proposed antenna covers 3.1–10.6 GHz with dual notched‐band characteristics and the mutual coupling below −20 dB. The antenna has a good diversity performance as the envelope correlation coefficient <0.03. The antenna is suitable for ultra‐wideband communications. [ABSTRACT FROM AUTHOR]

In this article, a design of planar cavity‐backed antenna‐triplexer is proposed for WLAN/WiMAX/ISM band at 5.2/5.5/5.8 GHz. The substrate integrated waveguide (SIW) technology is employed to realize a planar cavity‐backed antenna‐triplexer. The proposed geometry entails two SIW cavity resonators where a bowtie‐shaped smaller cavity is inserted inside the larger rectangular one. The rectangular cavity consists of two bent‐transverse slots those are excited by two different microstrip feedlines and the Bowtie‐like slot inside the Bowtie cavity, excited by a coaxial feed. The antenna generates three different resonances at 5.2, 5.5, and 5.8 GHz simultaneously with flat gain characteristics. By exciting cavity modes (TE110) by Port2/Port3 and a patch mode (TM010) by Port 1 simultaneously, average isolation of better than 23 dB is accomplished among the three input ports. To validate the proposed idea, the design is fabricated and experimentally tested. The measured responses show a good matching with the simulations. Moreover, the antenna shows front to back ratio better than 18 dB and simulated gain values of 7, 5.45, 4.75 dBi at the three resonances. [ABSTRACT FROM AUTHOR]

A compact three‐port tri‐band circularly polarized (CP) antenna for radio‐frequency identification (RFID) technique is introduced. Four inverted‐F radiating elements fed with a 90° phase delay feeding network realize the CP radiation at the FCC UHF‐RFID band (0.902–0.928 GHz). With the slot‐coupled feeding technique, Corner‐truncated slot and patch have been employed to achieve CP radiation at MW‐RFID bands (2.4–2.485/5.725–5.875 GHz). Decoupling structures are implemented to obtain excellent 20 dB port isolations during all operating bands. The relative impedance bandwidths in the three bands are 6.6%, 5.3%, and 5.1%, respectively, with peak gains of 2, 5.1, and 5.7 dBic. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to present a tri‐band bandpass filter (BPF) with compact structure. This filter consists of 50 Ω transmission line, varactor diode, positive‐intrinsic‐negative (PIN) diode, symmetrical square‐shaped half‐loop resonator pair, and three pairs of rectangular half circle that a T‐stub is placed in it. By using the add PIN and varactor diodes in the proposed structure, it is possible to connect and disconnect each band, and change the central frequency up to 400 MHz. In addition, there is a situation to disconnect and connect all three bands simultaneously and asynchronously (unconditionally). This filter contains a low ripple value in all three bands. In this regard, the maximum ripple value does not exceed 0.3 dB and rejection is greater than 25 dB in total stop‐band. An experimental tri‐band BPF has been developed for wireless fidelity, wireless local area network, and worldwide interoperability for microwaves access applications. The measured results are properly accommodated with simulated results. [ABSTRACT FROM AUTHOR]

This article presents a deca‐band multi‐input multi‐output (MIMO) antenna for full‐screen metal frame smartphone, which covers wideband of GSM850, GSM900, DCS, PCS, UMTS, LTE2300, LTE2500, WLAN/WiMAX, N78, and sub‐6 GHz (4.8–5.1 GHz) bands table. Two kinds of antenna structures are positioned on the long side edge and form two 2 × 2 MIMO array, covering the low‐band (824–960 MHz) and mid‐band (1710–2690 MHz/3300–3800 MHz), respectively. Four slot antennas are distributed on both sides of the short side edge. Each slot is connected to an antenna structure on the long side edge, sharing one port to form the high‐band structure. By reutilization the low and mid‐band structures, the high‐band structure can achieved a wide band bandwidth without any additional matching structures. The high‐band structure is composed of 4 × 4 MIMO array and covers the band of 4800–5825 MHz. A prototype of the proposed MIMO antenna is fabricated and measured. The isolation of the antenna is larger than 15 dB, the efficiencies are between 31% and 63%, and the ECCs is less than 0.3, which shows that the proposed antenna has great potential in the future 4G/5G smartphone application. [ABSTRACT FROM AUTHOR]

In this article, a low‐profile dual‐band patch antenna for vehicle communication is proposed. With two sets of shorting vias on the hexagonal‐shaped patch at different positions and single feed at the center, three different resonant modes are excited, forming two operating bands with omnidirectional and conical beam radiation respectively. The omnidirectional radiation at 2.45 GHz is used for wireless local area network (WLAN) communication while the conical beam radiation is used for cellular vehicle‐to‐everything (C‐V2X) communication. The proposed antenna is fabricated using the printed circuit technique. Both the measured reflection coefficient and radiation pattern match well with the simulations. With the advantage of low profile, dual‐band, and dual radiation characteristics, the antenna owns a good potential to be used in vehicle communications. [ABSTRACT FROM AUTHOR]

A compact bio‐inspired electromagnetic bandgap integrated wearable antenna (Bio‐EBG‐iwA) is proposed in this work. The Bio‐EBG‐iwA is based on the hybridization of semi‐Vitis vinifera leaf‐shaped patch, asymmetric feedline, reflected G‐shaped slot, partial ground, and a stub on the ground plane. The antenna is built on the locally made textile material called Aso‐oke (Alari) with permittivity and a loss tangent of 1.43 and 0.019, respectively. The dimension of the proposed antenna is 0.2λg×0.1λg×0.0089λg (22 mm × 12 mm × 0.7 mm) at 2.45 GHz. Despite its compactness, the gain of −0.48 and 2.5 dBi are achieved at 2.45 and 5.7 GHz respectively without electromagnetic bandgap (EBG). A dual‐band textile‐based uniplanar compact electromagnetic bandgap (UC‐EBG) is introduced to create isolation between the human tissue and the antenna. The dual‐band UC‐EBG is realized through the use of a modified slitted‐square ring (MSSR) and the 90° rotated H‐shaped patch on Aso‐oke (Alari) with a thickness of 2.1 mm. The periodicity of the proposed UC‐EBG is 34.5 mm. The antenna is placed on a 2 × 2 array of the proposed UC‐EBG separated by a 3 mm foam thickness. The radiation efficiency of 88.97% and 79.85% are achieved at 2.45 and 5.7 GHz respectively. The gain of the proposed UC‐EBG integrated antenna increased from −0.48 and 2.5 dBi to 5.9 and 10.7 dBi at 2.45 and 5.7 GHz, respectively. The front‐to‐back ratio (FBR) of 26.3 dB is achieved with the use of UC‐EBG. The use of UC‐EBG results in a 98.31% and 99.4% reduction in average SAR at 2.45 and 5.7 GHz, respectively. The off‐body and on‐body performance analysis of the proposed UC‐EBG integrated antenna show that the proposed EBG integrated antenna (Bio‐EBG‐iwA) is a suitable candidate for wearable application. To the best of our knowledge, this is the most compact wearable antenna with suitable gain, radiation efficiency, and high FBR. In addition, our proposed UC‐EBG shows that slitting is an effective way of miniaturizing the EBG structure. [ABSTRACT FROM AUTHOR]

A novel planar omnidirectional dipole antenna for wireless local area network (WLAN) applications is proposed. The antenna consists of a sleeve dipole antenna for the lower band and a cage dipole antenna for the upper band. Employing a unique planar composite structure, good dual‐band impedance matching can be achieved without an external matching circuit. The lower‐band dipole antenna adopts a sleeve structure, which reduces the size by bending in the middle and thickening at the end as inductance and capacitance loading, respectively. The upper‐band dipole antenna is embedded in the lower‐band dipole antenna, and the impedance bandwidth is broadened by adopting a cage structure and coupling with the lower‐band dipole antenna. The proposed antenna occupies an area of 0.38 λ0 × 0.08 λ0 (λ0 represents the wavelength of the lower frequency) on FR4 substrate of thickness 0.8 mm. The measured results show that the impedance bandwidths with a return loss more than 10 dB are 2.27–2.65 GHz and 4.89–6.02 GHz. The antenna has an omnidirectional radiation pattern, and both E‐plane and H‐plane have lower cross‐polarization levels. The average gain reaches 2.4 and 3.3 dBi in the 2.4‐ and 5‐GHz bands, respectively. The antenna is compact and easy to fabricate, and can be used for small omnidirectional WLAN terminal device. [ABSTRACT FROM AUTHOR]

In this article, a dual‐band shared‐aperture parasitic array radiator (DS‐PAR) antenna is presented to cover 2.4‐GHz WLAN lower‐band (LB) and 5‐GHz wireless local area network (WLAN) higher‐band (HB). The proposed antenna uses parasitic elements shared by both frequency bands, thus achieving the shared aperture of the dual‐band array. The antenna comprises of active elements for two bands, shared parasitic elements, reflective plate, and ground plane. The shared parasitic elements have different functions in the two frequency bands. The reflection parasitic elements in HB can be used in LB to achieve impedance matching and optimize the half‐power beamwidth. With a rotational symmetric structure, the antenna can generate three beams in 2.4‐GHz LB and six beams in 5‐GHz HB in horizontal plane, which covers full 360° range in both bands without communication blind zone. To validate the proposed design, a prototype is fabricated and measured. With the shared reflective plates, the dual‐band antenna works well in a shared space with a diameter of 0.73 wavelength in free space at 2.45 GHz. The antenna exhibits good impedance matching and high‐port isolation higher than 20 dB over the 2.4‐ and 5‐GHz bands. The realized gain is 4.81, 5.37, 5.30 dBi at 2.45, 5.25, and 5.8 GHz, respectively. The envelope correlation is lower than −35 dB within the bands of interest. [ABSTRACT FROM AUTHOR]

This reports the development of a dual port linearly polarized shorted triangular patch antenna for C‐ and J‐band with improved bandwidth and decoupled ports. Two orthogonal shorted walls and perforation on the patch have been conceived for improved bandwidth. L‐probe has been adopted to produce linear polarizations (LP). The shorted walls conceived on the equilateral triangular patch achieve higher compactness. The perforation in addition to the shorted wall enforces an overlapping response of the TM10, TM11, TM20 and slot modes resulting in an improved bandwidth. The slot mode and the TM10 mode overlap at the lower band. The TM11 and TM20 modes coupled together at the upper band. At the C‐band, it exhibits bandwidth ≥12.4%. Impedance bandwidth ≥36.4% with an isolation ≥23 dB is realized at the J‐band ports. It capitulates very stable gain of about 5 dBi at the lower band. At the upper band gain ≥7 dBi over 10–13 GHz is achieved and the maximum is 8.5 dBi. These gains are due to half of the equilateral triangular patch only. All these results are superior to the earlier reported investigations. Dual port communication ability is the enhance feature of the antenna. [ABSTRACT FROM AUTHOR]

In this communication, a compact dual‐element MIMO antenna with decoupling structure has been proposed for handheld devices. The proposed decoupling structure acts as a resonator and as a decoupling structure. The proposed antenna consists of nested slots in the radiator and it supports the application such as LTE, WLAN, Wi‐Fi, and WiMAX. The total size of the antenna is 30 mm × 10 mm. The impedance bandwidth of the antenna is 300/400/700 MHz, respectively. The decoupling structure consists of a feed line printed on one side of the substrate and swastika‐shaped array on another side. The power fed to the feed line coupled to the swastika‐shaped array for achieving the operating bands at 0.9 GHz and (8‐10) GHz. Meanwhile, the decoupling array provides isolation more than 20 dB at (2.3‐2.6) GHz, (3.4‐3.8) GHz, and (5.15‐5.85) GHz. The edge to edge spacing between the antennas is 10 mm. The percentage bandwidth of the antenna is 12.2/11.1/12.7/22.2%. The MIMO performance metrics such as envelope correlation coefficient, effective diversity gain, apparent diversity gain, and mean effective gain are evaluated. The proposed antenna is fabricated and tested. The measured results correlate with the simulated results. [ABSTRACT FROM AUTHOR]

This article presents a simple compact microstrip feedline printed antenna that can minimize the consequences of frequency interference, thereby, providing good stable omnidirectional radiation pattern and transmission response within whole range of desired frequencies. The proposed antenna has two regular shaped hexagonal radiators, a mictrostrip‐fed line and a partially extended ground plane perturbed by a circular slot inserted at the centre. The partial ground plane with a circular slot at the center plays an important role in the broad band characteristics of the proposed antenna, because they can adjust the electromagnetic coupling effect between patch and ground plane and improve the impedance bandwidth. The simulation and measured results are in close agreement and show that a wide bandwidth of 10.39 GHz (2.52‐12.91 GHz) at −10 dBi return loss with voltage standing wave ratio less than two is achieved by this antenna. The antenna is compact (0.37λ × 0.24λ), has good radiation pattern, appreciable gain of 5.97 dBi and 134% fraction bandwidth which is favorable for ultra‐wide band applications such as S, C, X, WLAN, and WiMAX. The equivalent lumped circuit model of the proposed antenna is also presented for validation purpose. The proposed antenna in particular focusses on 3.4 to 3.6 GHz frequency band with centre frequency 3.5 GHz (sub 6 GHz 5G band) and WLAN/Wi‐Fi (3.6/4.9/5.9 GHz) applications. [ABSTRACT FROM AUTHOR]

In this article, a flexible and compact tri‐band microstrip antenna is proposed for vehicular wireless applications. Triangular embedded radiators are employed to provide design freedom and minimize antenna size. Aiming at the bending demand and conformal modules, flexible polyimide‐based substrate is used for antenna fabrication. The measured results show that the proposed antenna operates at 1, 2.4, and 3.5 GHz, covering wireless local area network (WLAN) HaLow, WLAN, and world interoperability for microwave access bands. Benefited from its tri‐band operation, compact structure and flexible design, the proposed antenna is suitable to be integrated to wireless systems. The antenna occupies a compact size of 68 mm × 71 mm × 0.11 mm. For verification, the proposed antenna is integrated to a wireless high‐definition video transmission system. The system is composed of a 5‐megapixel camera, a video processor, a wireless network card, the tri‐band flexible antenna, and wireless terminals like smart phones. The measured results confirm high efficiency, mobility, and stability of the wireless video transmission system with the proposed antenna. [ABSTRACT FROM AUTHOR]

In this study, a frequency selective rasorber (FSR) is proposed where a transmission band at a higher frequency is achieved besides the lower broadband absorption. The FSR is designed by combining the individual designs of broadband absorber and bandpass frequency selective surface (FSS). The broadband absorption is achieved by placing the resistive and ground layer at a distance of around λ/4 at center frequency. The unit cell of bandpass FSS is designed by etching a double cross slot. The performance parameters at the transmission band are improved by a modified double cross slot, wherein a quarter of the slot is replicated on each corner of the unit cell. The bandpass FSS replaces the ground plane of broadband absorber, in the design of proposed FSR. The proposed FSR is a polarization‐independent structure exhibiting a broadband absorption from 3.1‐8.7 GHz (94.91%) along with a transmission band at 11.4 GHz. The working principle of proposed FSR is illustrated by an equivalent circuit model. A range for higher transmission frequency is determined for the proposed FSR, by studying the effects of bandpass FSS parameters on the transmission performance. A prototype of the proposed FSR is fabricated, and the results are experimentally verified. [ABSTRACT FROM AUTHOR]

In this article, gain‐bandwidth of microstrip antenna (MSA) fed half wavelength Fabry‐Perot cavity (FPC) antenna is enhanced by modifying partially reflecting surface (PRS) and artificial magnetic conductor (AMC) surfaces. Two methods are considered to analyze the resonant condition of FPC antenna. In the first method phase correction is applied, to take into account the modification in AMC layers, while in second method the entire AMCs and PRS surface of the structure is taken as a unit cell. The proposed antenna provides S11 < −10 dB, peak gain of 17.7 dBi with gain variation < 2 dB, side lobe level < −19 dB, cross polarization level (CPL) < ‐16 dB and front to back lobe ratio > 20 dB over 5.66 to 6.4 GHz, which covers ISM and satellite uplink C band. The overall antenna dimensions are 2.7λ0 × 3.1λ0 × 0.5λ0; here λ0 is the wavelength in free space corresponding to 5.8 GHz, center frequency of the ISM band. The measured results agree with simulated results. [ABSTRACT FROM AUTHOR]

In this communication, a new compact multiple‐input‐multiple‐output (MIMO) antenna design with frequency and port reconfigurable feature has been presented. The design consists of four orthogonally placed annular ring‐shaped UWB monopole elements. Wideband to narrowband switching of each monopole element is done by PIN diodes placed between the fed line and stepped‐impedance resonating stubs (SIRS). The reconfigurable frequency states are: UWB, mid‐band 5G and WLAN. In narrowband, frequency spectrum is tunable using varactor diodes placed at middle of SIRS. The antenna ports can be tuned to operate as 4‐port, or 2‐port MIMO and it is also possible that all the ports operate at different frequency simultaneously. The concept is proved by simulation and measurement results which includes S‐parameters, radiation patterns, gains, and envelop correlation coefficients. [ABSTRACT FROM AUTHOR]

In this paper, a novel multiple‐input‐multiple‐output tri‐band antenna with a featured embedded common mode (CM) choke is presented to prevent receiver desense and improve throughput for WLAN applications. The proposed antenna design consists of two wide‐bandwidth high‐efficiency electromagnetic structure elements with an Γ‐shaped branch and an open‐ended slot line in the element. The Γ‐shaped branch is used to reduce the size of the antenna element. The open‐ended slot line is a balun, which is used to reduce the CM current on the coaxial cable. The proposed antenna was simulated and measured, and the simulated results agree well with the measured ones. The results have also demonstrated that the proposed antenna is well suited for WLAN applications as it covers the three operating bands of 2.4G, 5.2G and 5.8G. [ABSTRACT FROM AUTHOR]

In this article, two configurations of dual‐band equilateral triangular dielectric resonator antennas (ETDRAs) for WLAN applications are proposed namely, configuration‐I and configuration‐II. The configuration‐I uses single ETDRA for dual‐band operation; whereas, configuration‐II includes two ETDRAs to operate as a dual‐band antenna. Both the antenna configurations, which uses 99.7% alumina material having a dielectric constant of εr = 9.9, are excited to operate in the bands of 2.4 to 2.5 GHz and 5.75 to 5.85 GHz. The antennas are excited using a conventional coaxial feed to have a simple feeding mechanism. Prototypes of both the antenna configurations are fabricated and measured. The radiation characteristics of the antennas are discussed. The circuit analysis for the proposed configurations of the dual‐band ETDRA is also performed and an appropriate equivalent circuit for each dual‐band ETDRA is presented. Further, the performance of the proposed configurations of the dual‐band antennas are also compared with other dual‐band DRAs reported in the literature. [ABSTRACT FROM AUTHOR]

A novel method for a single‐feed circularly polarized (CP) loop antenna with both broad impedance bandwidth and axial ratio (AR) bandwidth is presented based on characteristic mode analysis (CMA). The circular polarization characteristics are generated by exciting two orthogonal degenerate modes (DMs) via single feeding simultaneously. The 90° phase difference is achieved by loading the lumped inductors or capacitors. The wide bandwidth characteristics are generated by splitting a pair of DMs. Consequently, the two overlapping resonance points are split. The positions of feeding and loadings are determined with the aid of CMA. Compared with conventional methods, the presented method can simplify the feeding structure and provided a compact antenna. Based on this method, a loop antenna with two inductors is demonstrated for circular polarization application. The measured results show an impedance bandwidth of 47% and 3 dB AR bandwidth of 8.3% at 2.4 GHz wireless local area network (WLAN) bands. Both the simulated and measured results agree well. [ABSTRACT FROM AUTHOR]

This article is aimed to discuss a novel high directional flared quasi‐Yagi offset feed monopole UWB antenna. The proposed antenna is stamped on an FR‐4 dielectric material of dimensions 40 mm × 48 mm × 1.6 mm, which is exhibiting a permittivity of 4.4 and a loss tangent of 0.019. It operates within a frequency spectrum of 3.06 to 12.37 GHz that includes the complete FCC ultra‐wideband of 3.1 to 10.6 GHz. Maximum peak gain and radiation efficiency of this antenna are found to be 10.07 dBi at 10.4 GHz and 92.64% at 4.7 GHz, respectively. The presented antenna employs a novel structure comprising of flared elements, directors and offset feed to a planar monopole for achieving directional behaviour. Thanks to the novel technique for enhancing uni‐directional characteristics in the entire operating band. Prototype of the proposed structure is fabricated and measurement results are verified with the simulation results. A good matching is also found between them. [ABSTRACT FROM AUTHOR]

A compact dual‐band antenna is designed in this paper, which consists of a pair of lower band (LB) element and four higher band (HB) elements operating at 0.69 to 0.96 GHz and 3.3 to 3.6 GHz, respectively. Four HB elements are put between the adjacent dipole arms of LB element. All of elements are at the same height, and having their own reflector. A designed dual‐band dual‐polarized antenna at high frequency ratio will be fulfilled without added any other structure. The fabricated antenna sample has been measured, results show that the average gains of LB and HB elements are 8.48 dBi and 8.44 dBi and the half power beam widths are 69.1° ± 9° and 60.7° ± 8.5°, respectively. Moreover, dual‐polarized property of both LB and HB is checked. The cross‐polarization discrimination values are greater than 15 dB. The proposed antenna is implemented the coverage of two bands with high frequency ratio with a simple structure, and the antenna with both low profile and high gain characteristics. All of the results demonstrate that the antenna radiation boasts its favorable performance and can be a good candidate in 5G mobile communication system for sub‐6 GHz base stations. [ABSTRACT FROM AUTHOR]

The design of a compact triple band notched Frequency Selective surface (FSS) at Ultra‐Wide‐Band (UWB) frequency range is presented. To make the proposed FSS polarization insensitive, on the upper part of the substrate a single metallic square loop (SL) and four identical rotational symmetric square split ring resonators (SSRR1) are placed, whereas at the bottom part another four identical rotational symmetric SSRR loops (SSRR2) are printed. Here each SSRR is rotated in 90°clockwise direction over a single layered FR4 substrate. Triple band notches are obtained at WiMAX and Satellite communication downlink C‐band (3.3‐4.2 GHz), WLAN (5.1‐5.9 GHz) and Satellite communication X‐band (7.2‐8.4 GHz) for both TE and TM polarizations. Angular stability is achieved until 70° and attenuation of more than 25 dB is observed at resonance. The passband is obtained at 4.37 and 6.22 GHz. The proposed structure separates the closely spaced frequency bands by a ratio of 1.44 and 1.39 at the stop band and 1.42 at the pass band. The dimensions of the proposed FSS unit cell are 0.13λ0 × 0.13λ0 × 0.020 λ0, where λ0 represents the free space wavelength at the lowest resonance frequency. Good agreement between modeled and measured results is obtained. [ABSTRACT FROM AUTHOR]