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Ever‐increasing bandwidth requirements from various industries drive the need for the ever‐increasing bandwidth of antennas used for testing. Broadband Double‐Ridged Guide Horn (DRGH) antennas are used extensively in antenna measurement and ElectroMagnetic Compatibility/Interference (EMC/I) testing. The current state‐of‐the‐art broadband DRGH antennas reported in the literature for use in measurement applications cover bandwidth ratios as large as 36:1 (0.5–18 GHz). This paper presents the design and realisation of a DRGH antenna with a 100:1 bandwidth ratio (0.5–50 GHz). To achieve such a wide bandwidth, the ridge gap, width and feed were optimised, and a novel coaxial‐to‐ridge waveguide launcher section based on a typical Vivaldi antenna was developed. Backward radiation was reduced using an absorber‐filled cavity. A prototype DRGH antenna was manufactured using additive manufacturing, also referred to as 3D printing. Simulated and measured results obtained in an anechoic chamber are presented. [ABSTRACT FROM AUTHOR]

This article presents a millimetre‐wave (MMW) wideband multibeam antenna array with a pillbox transition using multilayer low‐temperature cofired ceramic (LTCC) technology. The mushroom structure with dual resonant modes offers wideband performance for radiating array, while an integrated pillbox reflector achieves multibeam scheme. To reduce the design complexity of electrically large pillbox system, two popular pillbox transitions are investigated with a unit model method. The proposed unit model can be used to predict the transmission performance of pillbox reflector in any incident angle. Moreover, the mushroom antenna array and power divider fed by quasi‐TEM wave are also designed using unit model, greatly simplifying the design of electrically large pillbox antenna array. In the final design, the long‐slot pillbox transition, rather than multi‐slot transition, is selected due to its ultrawideband performance and simple structure. The proposed LTCC prototype is analysed and fabricated, obtaining a good agreement between simulation and measurement. The measured results show a −10 dB impedance bandwidth of 17.6% from 31 to 37 GHz, and five beams with ±45° scanning range is achieved with sidelobe level lower than −10 dB. [ABSTRACT FROM AUTHOR]

This article presents a wideband circularly polarised (CP) antenna array using a miniaturised double box branch‐line coupler. This was achieved by creating a slow wave structure by introducing open‐circuit stubs on the inside arms of the branch‐line coupler. The 2 × 2 antenna array is made of four CP slot radiating elements excited through 1 × 4 feeding network. Moreover, sequentially rotation method is used to increase the axial‐ratio (AR) bandwidth of the array. The CP slot radiating element is fed by coplanar waveguide. The feedline of the horn‐shaped radiator includes a circular matching stub. Ground connected asymmetric T‐shaped stub, a pair of grounded L‐shaped square strips, and single strip line are shown to induce CP and enhance the antenna's 3 dB impedance bandwidth and AR performance. The antenna constituting the array has impedance bandwidth of 2.45 GHz from 4.8 to 7.25 GHz that corresponds to a fractional bandwidth of 40%, and its 3 dB AR extends between 4.8 and 6.25 GHz. Compared to a conventional double‐box branch‐line coupler the size of the proposed coupler is reduced by 35% by increasing the capacitance of the coupler's arms. This also is shown to increase the impedance bandwidth of the coupler. A 2 × 2 array was fabricated, and its performance verified. Measured results confirm the proposed antenna array exhibits CP covering the bands of WiMAX IEEE 802.16, C‐band and ITU‐R F386.9. The measured 3 dB AR bandwidth of the antenna array extend from 3 to 7.3 GHz and its impedance bandwidth extends from 3.2 to 9.0 GHz. The antenna array radiates with a peak gain of 11.5 dBic. [ABSTRACT FROM AUTHOR]

In this article, the authors propose a super wide band CPW‐fed fractal monopole antenna suitable for phased array antennas with a shaped beam radiation pattern, operating in the frequency ranges below and above 1 GHz at the same time. The antenna has an octagonal radiator with fractals of the same shape added to its edges and sides. Also, the symmetrical elliptical ground planes have reduced the antenna size and, consequently, the mutual coupling in the antenna array. Despite the super‐wide frequency range, the antenna's radiation pattern is relatively steady in the E‐plane, and the negligible ripple on the radiation pattern makes it suitable for shaped beam radiation patterns in phased array design. The single‐element antenna with an overall size of 0.24λ × 0.38λ at 500 MHz is printed on an FR‐4 substrate. The outcomes of the simulation and measurement are well agreed in the frequency band of [500 MHz to 5.5 GHz] with an impedance bandwidth (|S11|< −10dB) of 166.67% and VSWR< 2. Also, the fidelity factor of the antenna is studied to investigate the SWB performance. [ABSTRACT FROM AUTHOR]

A broadband dual‐polarised antenna with L‐shaped strips for long‐term evolution (LTE)/5th generation mobile networks (5G) is proposed in this article. Based on the principle of multi‐mode resonance, wide bandwidth is achieved with L‐shaped strips and H‐shaped strips. The metal strips and dipoles are printed on the same substrate, which also contributes to antenna miniaturisation. The short pins are designed for impedance matching and improving isolation. The metal reflector is designed to control beamwidth and increase gain. A prototype was fabricated using an easy Printed Circuit Board technique to verify the proposed design. Low‐profile of 0.2λ0 (λ0 is the free‐space wavelength at the centre frequency) is achieved. The measured results show that the relative bandwidth is 74% (2.3–5.0 GHz) at Voltage Standing Wave Ratio <1.8 while the isolation is more than 24 dB covering the LTE/5G modern band. In addition, the in‐band average gain is 9 dBi. [ABSTRACT FROM AUTHOR]

A broadband substrate integrated cavity (SIC) antenna array based on high‐order mode is proposed for low‐temperature cofired ceramic (LTCC) integrated systems in W‐band. To improve the gain of antenna element, a large SIC is adopted to work in high‐order mode, which also avoid using excessive vias and reduce the process complexity. Two parasitic patches are loaded on the high‐order mode SIC to remove the reverse E‐field in the open aperture, leading to a high‐gain broadside radiation. The high‐order‐mode SIC antenna element is fed by high‐order TE20‐mode substrate integrated waveguide (SIW), rather than regular TE10‐mode SIW. The simplified feeding network with TE20‐mode SIW is also designed with wideband performance, further enhancing the fabrication robustness of antenna array. To validate the proposed high‐order mode‐based antenna element and feeding network, a W‐band 2 × 4 antenna array is designed as an example using LTCC technology. The measured return loss is better than 10 dB from 81.1 to 98.1 GHz (19% bandwidth) with a maximum gain of 18.3 dB at 94 GHz. The proposed antenna array has great potential in millimetre‐wave and terahertz LTCC integrated applications. [ABSTRACT FROM AUTHOR]

A W‐band dual‐beam low side‐lobe level antenna with a shared slotted waveguide radiating layer was designed by the authors. The proposed antenna consists of a symmetrical dual ports feed network layer located on two sides of the antenna, a novel shared symmetrical 4 × 32 slotted waveguide array radiation layer, and a bottom layer. The compact slot distance was adjusted to achieve deflection of the radiation pattern and reduce the radiation grating lobes. Good antenna radiation efficiency and port isolation were obtained by optimising the position of the slots at the radiation layer. A low side‐lobe level (SLL) was obtained using Taylor distribution was used in the design of the offset of each slot. The optimised antenna was fabricated and measured. Based on measurement results, the designed antenna has a 24.8 dBi far‐field gain, −17/–25.5 dB E/H plane side lobe level, and 19.8° beam deflection at 94 GHz. The performances of the two ports were in good agreement with each other, and the measured isolation was above 14.5 dB at 94 GHz. [ABSTRACT FROM AUTHOR]

The present is a low‐profile, wide‐angle scanning, ultrawideband, tightly coupled dipole array that lacks a wide‐angle impedance matching layer and lossy materials. Impedance matching will deteriorate at the lower end of the operating bandwidth due to the influence of the ground plane. A well‐designed perforated balun is used to achieve better impedance matching. Moreover, parasitic metallic strips are attached to the dipole's side to add additional reactive components. According to the results of simulations, the impedance bandwidth of the array, which ranges from 0.67 to 2.83 GHz, and its wide‐angle scanning capability, which scans 75° in the E‐plane and 45° in the H‐plane, both achieve good performance when the voltage standing wave ratio is less than 3. The profile of the array is only 0.0581λlow above the ground plane, where λlow is the wavelength at the lowest operating frequency. The proposed array's simulated results are validated by fabricating and measuring an 8 × 8 prototype array. [ABSTRACT FROM AUTHOR]

The design, fabrication, and measurement of a 7 × 7 mm‐wave array antenna have been presented for 5G communications. The substrate integrated waveguide (SIW)‐fed antenna element is formed of four parts: a rectangular radiating patch, a coupling slot cut onto the broadwall of the SIW, a transition layer, and a feeding layer at the bottom. The bandwidth and radiation efficiency has been improved by embedding an air cavity below the radiating patch, as the effective dielectric constant of the substrate is reduced. Moreover, a prototype has been fabricated and measured to verify the design principles. The finite array operating over 23–28 GHz has achieved active voltage standing wave ratios of less than 2 and 2.5 in the E‐ and H‐planes while scanning up to 45° respectively. Compared with the theoretical ideal gain, the average gain drop of the measured embedded element gain is 0.73dB. [ABSTRACT FROM AUTHOR]

In this paper, a wide‐angle beam scanning circularly polarized (CP) phased array element, which consists of a concentric tightly coupled dipole array (TCDA) element with a two‐layer parasitic ring structure and a wideband 90° phase shifter, is proposed. To solve the problem of the scanning blindness zone caused by a concentric layout, the grounded coupling patch for the traditional TCDA element is 'split' into a combination of a grounded parasitic ring and coupling patch. This combination structure can not only suppress the in‐band common‐mode resonance but also destroy the scanning blind zone mode formed by the dipole and grounded coupling patch. In addition, a two‐layer parasitic ring structure is introduced to obtain a wider axial ratio (AR) beamwidth relative to a single‐layer structure, so a wide‐angle beam scanning AR is realized. An 8 × 8 left‐handed CP planar array based on the proposed wide‐angle beam scanning CP elements is designed and prototyped. Results show that the array can operate over a 3.2:1 (3.75–12.0 GHz) overlapping bandwidth, meeting an AR < 3 dB in the main beam and an active voltage standing wave ratio <2.8 within a ±60° angle scanning range. [ABSTRACT FROM AUTHOR]

A wideband, metal‐only, and low‐cost transmission‐type polariser is proposed in which a plane wave with linear polarization impinging on the structure is converted to circular polarization wave on the other side and vice versa. The proposed structure is a quad‐layer frequency selective surface that its unit cell is composed of two sets of multi‐slot elements placed perpendicular to each other to achieve a wideband polariser. In this unit cell, by changing the length of the slots, the amplitude and phase of transmission coefficient can be controlled, which are used to create a 90‐degree phase difference between vertical and horizontal components of the incident electric field. A 9×9 $9\times 9$ array of the proposed polariser with a quad‐layer is simulated and fabricated that shows the bandwidth of 22% (11.7–14.7 GHz) for an axial ratio below −3 dB and a transmission efficiency of more than 85%. [ABSTRACT FROM AUTHOR]

A circularly polarized antenna suitable for integration into the framework of smartwatches is reported in this manuscript. The proposed antenna operates in the industrial, scientific and medical band of 5.8 GHz with a footprint of about 45 × 15 × 1.6 mm3 (0.8 λ × 0.2 λ × 0.03 λ) and is excited by a coplanar waveguide line loaded with an L‐shaped radiator patch. The antenna prototype was studied in free space and then adapted to on‐body scenarios using computer hand models. The performance of the antenna was validated in measurement in a realistic human hand, and the antenna achieves satisfactory on‐body performance; measured and simulated results are in good agreement. Furthermore, for health risk concerns related to exposure to electromagnetic radiation, the specific absorption rate (SAR) analysis for the smartwatch on wrist‐worn has also been presented which is far below the normal SAR criteria according to IEEE C95.1 guidelines. The simple structure of the proposed antenna and its high performance make it an ideal candidate for smartwatch applications in health care monitoring purpose. [ABSTRACT FROM AUTHOR]

A high gain vertically polarised travelling‐wave frequency scanning array antenna fed by a meander rectangular waveguide is presented for Ku‐band operation. The proposed antenna is used in a radar demonstrator setup to detect and monitor birds in direct proximity to the wind farms. The goal is to prevent collisions of birds with wind farms. The proposed antenna consists of 34 inclined dumbbell‐shaped radiating slots integrated with a parallel‐plate waveguide. The proposed meandered feeding structure is used to enlarge the beam scanning angle range over frequency. The dumbbell‐shaped radiating slots are employed in the narrow wall of the meandered waveguide due to the space restriction of the meandering. The parallel‐plate waveguide is used as a polarisation filter to reduce the cross‐polarisation level of the proposed antenna owing to the inclination of the radiating slots. An E‐plane horn is used to reduce the beamwidth in the elevation plane. The overall size of the antenna is 20.6λ in length and 15λ in width, where λ is the free space wavelength at 15.55 GHz. The antenna operates in the frequency range from 15.40 to 15.70 GHz. The half power beamwidth is about 4° in the azimuth plane and about 20° in the elevation plane at 15.55 GHz. The main beam of the antenna steers over frequency to cover 39° of angular range in the azimuth plane. A Taylor distribution is applied to achieve sidelobe level below −25 dB in the same plane and 26 dBi gain over the operating frequency range. The antenna array is fabricated and measured successfully to verify the proposed approach. The fabricated antenna shows an impedance matching significantly better than 10 dB in the operating frequency. The measured gain is higher than 25 dB throughout its frequency range. [ABSTRACT FROM AUTHOR]

In this paper, the slow‐wave coplanar stripline (S‐CPS) technology is utilised to design high performance and small footprint resonators operating within the millimetre‐wave band from 50 to 80 GHz. The proposed resonators are designed based on high quality factor quasi‐lumped capacitances and inductances offering a great flexibility in terms of design. The derivation of these components from the S‐CPS is explained theoretically and their behaviour is validated by EM simulation; an equivalent electrical model is also developed. The proposed concepts are demonstrated in the BiCMOS 55‐nm technology, and a good agreement between modelling, EM simulation and measurement results is achieved. The proposed devices could later be considered as interesting elementary blocks for the design of mm‐wave filters. [ABSTRACT FROM AUTHOR]

In this study, a novel broadband circularly polarised waveguide slot array antenna with a wide axial ratio bandwidth is designed. The circular polariser is excited by the waveguide radiation linear polarised antenna, whose end is bent by 90° and generates a circularly polarised electric field. The matching waveguide between the slot and the polariser improves impedance matching. Furthermore, the structure with the added waveguide changes waveguide impedance, which can be used to realise impedance matching, and reduces the spacing between the units. In this study, a 4 × 4 antenna array is fabricated. The measured results reveal that the array achieves −10 dB impedance bandwidth of 27% (11.15–14.63 GHz) and the 3 dB axial ratio bandwidth of 23% (11.48–14.52 GHz). An aperture efficiency higher than 71% is obtained, with the maximum gain of 22 dB. The antenna side lobes levels are less than −13 dB in the operating bandwidth. [ABSTRACT FROM AUTHOR]

This study presents for the first time the feasibility of a coplanar isolator using YIG material for applications in the Ku, K and Ka bands. The proposed structure is an asymmetric coplanar waveguide with a transverse array of unopened slots etched on a ground plane. Such structures are characterized by several cut‐off frequencies on the transmission parameters. With a low dc magnetic field of 72 kAm−1 applied along with the slots, significant nonreciprocal effects greater than 20, 19 and 29 dB are obtained at 13.95, 23.39 and 39.61 GHz, respectively. The proposed structure can be used as a multiband isolator for microwave applications. The low biasing field of this multiband isolator and its compactness (88 mm2) are its main advantages, which makes this structure particularly suitable for integration. [ABSTRACT FROM AUTHOR]

This study presents integration of complementary CMOS active feedback low noise amplifier with coplanar waveguide fed patch antenna for Wi‐Fi networks. The LNA design‐I, involves a cascode amplifier followed by active feedback common source amplifier offering wideband impedance matching with lowered parasitic losses. The inductor‐less feedback mechanism is used to nullify noise effect with extended bandwidth in the range of 2.2 to 5.8 GHz and a peak forward gain of 22.5 dB. It is implemented on agilent's advance design system using 45 nm CMOS process. The noise figure (NF) is approximately 2 dB while the stability factors µ and µ prime are well above 1 dB with IIP3 of about 15 dBm. The chip area is 0.57 x 0.57 mm2 under dc power supply of 1V while power consumption of 0.8 mW. A CPW fed antenna design‐II, achieves a wide band response similar to the bandwidth of LNA. The size of the fabricated antenna is calculated as 40 x 40 mm2. The peak gain is approximately 4.1 dBi at 3.9 GHz. The codesign‐III, proposes a receiver achieving a much wider band of 1.6 to 6 GHz with a gain of 16.5 dB and NF of 2.59 dB at 2.06 GHz. The codesign improves the system integration by reducing overall chip area and offers saving in the effective cost. [ABSTRACT FROM AUTHOR]

This study proposes a novel radiating element to enhance the bandwidth of a substrate-integrated waveguide-based resonant slot array antenna. Unlike the conventional scheme, the proposed element has two parallel slots of unequal length. The long slot dominates the radiation, while the short one deals with the matching. An amplitude-tapering power divider was integrated into a $5\times 4$5×4 element array to restrain the E-plane sidelobe level (SLL). The measured $-10$−10 -dB bandwidth is 23.14–25.4 GHz (9.42% @24 GHz). The E-plane and H-plane SLLs are $-$− 22.04 and $-$− 30.34 dB, respectively. The cross-polarised levels in the operating band are $\lt -$<− 30 dB and a peak gain of 17.77 dBi was measured at 24.2 GHz. A good agreement is observed between the simulated and measured results and then validates the feasibility of the bandwidth-enhanced slot pair proposed herein. [ABSTRACT FROM AUTHOR]

Here, a near-zero permittivity (ε) and permeability (μ) metamaterial superstrate is presented as a decoupling structure for a multiple-input-multiple-output (MIMO) antenna. The proposed design offers peak isolation of 41 dB with reduced edge separation of 0.042λo at the resonating frequency. To verify the simulation results, the prototype of the proposed superstrate and antenna is fabricated and tested. The two-element MIMO antenna has -10 dB impedance band of 5.5-5.92 GHz with a peak measured gain of 7.41 dBi and efficiency above 78%. The measurement results ensure an isolation enhancement of 30 dB with a correlation coefficient of <0.26 within the operating band. The proposed method offers a good design technique for high gain and a closely packed MIMO antenna system for WLAN applications. [ABSTRACT FROM AUTHOR]

A new technique for lowering the sidelobe level (SLL) of the microwave and millimetre-wave antipodal Vivaldi antenna (AVA) has been presented in this study. The technique is based on introducing tapered-shape Teflon surrounding AVA to couple energy propagated from the antenna and produce stronger radiation in the end-fire direction and as a result, it offers wideband low SLL. Some features of the presented antenna with the utilised new technique are summarised as follows: high gain in wide bandwidth corrected tilt of beam on E-plane in wide bandwidth and low cross-polarisation level. The presented antenna is fabricated and the magnitude of the reflection coefficient of the fabricated antenna is tested, which is from 3.2-40 GHz with S11 < -10 dB. It exhibits an average of SLL < -10 dB in E-plane and SLL < -18 dB in H-plane at a wideband of 3.2-40 GHz. Moreover, the lowest E-plane's SLL of -20 dB is achieved over the frequency band of 7-7.5 GHz. The proposed antenna has a small size of 43 (width) × 108 (length) mm2. The proposed antenna with the mentioned features becomes an attractive candidate for imaging applications. [ABSTRACT FROM AUTHOR]

In this study, a rhombus-shaped patch antenna is proposed using metamaterial transmission line. The motivation of this work is to overcome the problem of low gain while designing miniaturised antennas. The proposed design is based on coplanar waveguide feeding technique. A rhombus-shaped patch is chosen in this structure in which striplines are provided to connect the ground planes and to obtain the shunt inductance. Asymmetric meandered line inductors are integrated with the striplines for miniaturising the electrical size of the antenna. Further to improve the gain of the antenna in the lower bands, asymmetric ground plane and complementary closed ring resonator have been employed in the proposed structure. The electrical size of the proposed antenna is 0.168λ0 x 0.151λ0 corresponding to the physical size of 25 mm x 22.5 mm, where λ0 = free space wavelength at 2.02 GHz. Considering below -10 dB input reflection coefficient, this antenna operates in three bands covering 1.96-2.07, 4.06-4.72, and 6.43-7.79 GHz. In addition, the proposed antenna exhibits gain of 1.49, 2.68, 2.19, and 4.31 dB at 2.02, 4.48, 6.72, and 7.43 GHz, respectively, in the maximum direction of radiation. [ABSTRACT FROM AUTHOR]

This study proposes the design of broad-band microstrip loop antennas with less-dispersive group velocity of radiation patterns for accurate direction of arrival (DoA) estimation. The proposed structure consists of radiating and feeding microstrip loops, and the radiating loop is electromagnetically coupled to the feeding loop. This feeding mechanism helps to suppress phase variations of radiating patterns by avoiding dual resonances within a wide frequency band over 60 MHz, which allows to obtain the less-dispersive group velocity for accurate DoA estimation. The effectiveness of the less-dispersive behaviour is validated by implementing the proposed structure into a four-element array to estimate vertical and horizontal placements using dual-axis phase interferometry. The results confirm that the proposed antenna has less-dispersive group velocity compared to a conventional microstrip patch antenna and is more suitable for accurate DoA estimation. [ABSTRACT FROM AUTHOR]

A coplanar waveguide fed metamaterial antenna based on two-unit cell composite right/left handed transmission line (CRLH-TL) loaded with resonating rings is presented. The bandwidth is enhanced by merging the zeroth-order resonance and first positive-order resonance of CRLH-TL with two additional resonances due to resonating rings. The measured results show a - 10 dB fractional bandwidth of 71.11% (2.9-6.1 GHz) with realised gains of 2.35, 3.2, 3.75 and 3.6 dBi at the resonant frequencies 3.4, 4.3, 5.3 and 5.7 GHz, respectively. The peak realised gain is found to be 4.5 dBi at 4.9 GHz. The simulated radiation efficiency is >61% for the entire band of operation with a peak value of 88.75%. A good agreement is found between measured and simulated results. The proposed antenna is suitable for WiMAX (3.3-3.8 GHz) and WLAN (5.15-5.85 GHz) applications. [ABSTRACT FROM AUTHOR]

This study presents a new design of a reduced volumetric ultra-wideband (UWB) antenna using innovative dielectric based on the use of geopolymer material which is safe and eco-friendly. The created antenna is intended to radiate in the air. The impedance mismatch due to interface dielectric/air at the aperture of the antenna imposes to choose dielectric material with an appropriate permittivity value. In this study, the authors focus on the experimental protocol that they use to elaborate a dielectric material with suitable dielectric properties over an UWB domain. An experimental phase of dielectric properties assessment is also described. The conceived antenna is inspired by K-antenna which constitutes the starting point of the proposed new antenna design, particularly because of their small dimensions. The antenna is intended to operate in a frequency band ranging from 300 MHz to 3 GHz. The authors demonstrate that the use of an appropriate innovative dielectric material like a geopolymer is an efficient way to reduce the antenna size. Furthermore, the behaviour of the antenna filled with geopolymer is validated using experimental results. [ABSTRACT FROM AUTHOR]

A novel low profile log-periodic array with vertically polarised end-fire radiation patterns is proposed in this study. It totally consists of 22 antenna elements with three different types of monopole antennas. Specifically, conventional monopoles were utilised at the high end band, while monopoles with different types of top-hat loadings were designed for lower frequency band operation. Shorting posts are strategically introduced to maintain a good impedance matching at the lower band. A folded microstrip line is printed on the back side of the ground plane to feed the array. The log-periodic monopole array achieves a very low profile of 0.063 λl, where λl is the wavelength at the lowest operating frequency in free space. Moreover, the array also exhibits an extremely narrow width of 0.075 λl in the transverse dimension, which makes the array an attractive candidate for phased array development along the transverse direction. A prototype of the array is fabricated. Measured results show that the array achieves a minimum realised gain of 4.5 dBi across a wide frequency band of 1.19-11.7 GHz (9.83:1). [ABSTRACT FROM AUTHOR]

An ultra‐wide bandwidth, high‐efficiency, small‐size and low‐profile waveguide antenna is presented in this study. To extend the bandwidth without increasing the antenna size, the bowtie shape slot and the stepped square coaxial transition in a ridged waveguide cavity are utilised. The proposed antenna is well suited to use as an element for the phased array with the wide‐angle scanning capability, and such array is a good candidate for the synthetic aperture radar (SAR) application. The development of an active solid phased array (ASPA) utilising bowtie slot waveguide antenna as the element is presented to illustrate the design procedure. The proposed ASPA is fabricated and the measured results are provided to demonstrate that the proposed array has good performance in field pattern and impedance matching over the full X‐band (8–12 GHz). The ASPA's operating frequency band is cantered at 10 GHz with bandwidth 40%. This ASPA has been integrated into the latest SAR system with the maximum ground resolution of 0.05 m, and the SAR image is also provided at the end of this study. [ABSTRACT FROM AUTHOR]

In this study, the authors introduce a new and systematic procedure for the design and optimisation of a conductor‐backed coplanar waveguide low‐pass filter (LPF). The width of the centre conductor (i.e. signal trace) is modelled in a truncated Fourier series, whereas the gap to the adjacent grounds is maintained constant relative to the width variation. Transmission lines theory is adopted to model the LPF and establish an optimisation setup. Three optimisation techniques; namely, trust‐region‐reflective algorithm, symbiotic organism search, and genetic algorithm are investigated to minimise the developed bound‐constrained non‐linear objective function. To verify the proposed procedure, an LPF with a cutoff frequency of 2 GHz is optimised, simulated, and measured. The transmission parameter in the passband is found to be in the range −0.3 ± 0.1 dB, and better than −30 dB in the stopband. [ABSTRACT FROM AUTHOR]

In this study, a coplanar waveguide-fed reconfigurable antenna using crescent-shaped fractal geometry is presented. The frequency reconfigurable approach is obtained using radio-frequency positive intrinsic negative diodes, resistor, and inductors. The proposed approach has successfully allowed reconfigurable switching up to eight frequency bands between 1.46 and 6.15 GHz. Good results have been obtained in terms of stable and omnidirectional radiation patterns. The realised gains of the antenna system, in these frequency bands, vary from 0.52 to 5.67 dBi. The designed antenna has the advantages of a multiband structure and compact size over the previously reported structures. The proposed antenna is suitable for future wireless application systems. [ABSTRACT FROM AUTHOR]

For reference antenna without parasitic patch, it covers the impedance operations from 1.72 to 4.73 GHz and 5.38 to 6.62 GHz with ∣S11∣≤-10 dB, and has dual sense circular polarisation (CP) between 3.4 and 3.8 GHz (11.1%), between5.5 and 5.63 GHz (2.3%), respectively. In this study, to further improve the performance, an enhanced coplanar waveguide fed dual CP broad bandwidth antenna is proposed by using the C-shaped parasitic patch. It covers the impedance operations from 1.72 to 6.6 GHz with ∣S11∣≤-10 dB, the 3-dB axial ratio between 2.92 and 4.04 GHz (32.2%) for left-hand CP as well as that between 5.42 and 5.63 GHz (3.8%) for right-hand CP are achieved. Compared with reference antenna, it is obviously that the proposed antenna achieves a remarkably enhanced dual CP with wider resonant bandwidth. Furthermore, the measured results and simulated results are agreement well with each other. [ABSTRACT FROM AUTHOR]

A polarisation independent artificial magnetic conductor (AMC) miniaturised using interdigital capacitors is investigated. Its performance is analysed and compared with two other previously reported AMCs. Then, a circularly polarised square slot antenna (CPSSA) utilising the proposed AMC as a reflector is implemented, which achieves unidirectional radiation and low profile simultaneously. The CPSSA is fed by a coplanar waveguide and loaded by two L-shaped strips placed around two diagonal corners, providing the required perturbation for circular polarisation radiation. In between the slot antenna and the AMC reflector is an air gap layer. The performance comparison of the whole antenna system employing different reflectors (three AMCs and one perfect electric conductor (PEC)) proves the advantage of the proposed AMC. As for the fabricated antenna prototype, the measured 10 dB return loss impedance bandwidth and 3 dB axial ratio bandwidth are 15.9 and 4.1%, respectively, corresponding to the centre frequency of 2.71 GHz. In addition, an almost constant gain of around 5.5 dBic has been obtained across the circular polarisation bandwidth within an overall antenna volume of 0.54λ0×0.54λ0×0.08λ0. [ABSTRACT FROM AUTHOR]

A compact wideband coplanar waveguide (CPW)-fed antenna is designed for body implantable applications. The proposed antenna has an electrical dimension of only 0.42λ x 0.42λ x 0.0072λ at 2.3 GHz resonating frequency. Fractional bandwidth of 93.5% (1.35-3.5 GHz) is achieved with the low-profile antenna. To understand the extent of miniaturisation and bandwidth enhancement of the antenna, the characteristic modal analysis is performed. The wideband feature is achieved with the application of asymmetric complementary split-ring resonator structure through multiple mode excitations. Additional miniaturisation and impedance matching are obtained with a pair of asymmetrical arc-shaped annular ring slots within the main radiator. The substrate and radiator have been realised using silicon and gold due to their inherent property of excellent biocompatibility with the human body. Single layer, as well as multi-layers phantom model, was used to assess the performance of the antenna. Owing to the inherent wideband feature of the designed antenna, it is able to cover the desired band efficiently even after detuning in different phantom models. The designed antenna is tested in vitro with the development of proper muscle mimicking liquid and the measured results are found to be in good agreement with the simulated ones. [ABSTRACT FROM AUTHOR]

This study investigates a particular type of ground plane modifications in ultra-wideband (UWB) antennas and the effect they have on achievable amount of miniaturisation of the structure at hand. The focus is on n-section rectangular slits below the feeding line. The authors analyse possible size reduction as a function of the number n of slit sections. In order to ensure that the minimum antenna footprint is obtained in each case, rigorous numerical optimisation of all antenna parameters has been carried out. The optimisation process is constrained to guarantee that the antenna exhibits acceptable in-band matching at the level of -10 dB. For the sake of generality, the study has been performed using a benchmark set of four representative UWB monopoles. The results clearly indicate a significant advantage of increasing the number of degrees of freedom of the ground plane slit but also the saturation effect, i.e. decreasing advantages of introducing additional slit sections beyond a certain value of n. The average amount of miniaturisation for n = 5 versus n = 1 is around 40%. For selected designs, numerical results have been validated experimentally. [ABSTRACT FROM AUTHOR]

A palm-sized antenna is proposed for the hybridisation of fifth generation (5G) and long-term evolution-advanced (LTE-A) communication modes. The antenna has the overall volume of 70 mm (l) × 40 mm (w) × 0.254 mm (h) clutched by four multiple-input-multiple-output chip antennas (CAs) operating at 2.4 GHz for LTE-A on the sides of a flat substrate integrated waveguide (SIW) four-by-four Butler matrix (BM) beamforming antenna operating over the band from 27 to 29 GHz for 5G communication. Advantages are the broad bandwidth gained by a low-profile BM and this metal SIW structure of high isolation above 10 dB with neighbouring CAs, which is impossible for the microstrip BM and coplanar waveguide (CPW) version. The simulated and measured results of the impedance matching as well as the gains and radiated field patterns of all the ports reveal the antenna is proper for the multi-mode communication as a compact geometry. Besides, high isolation between the closely placed radiating elements is observed. [ABSTRACT FROM AUTHOR]

In this study, a new design of a planar ultra-wideband (UWB) monopole antenna with a rose-curve contour shape is proposed. The rose-curve circumference of the monopole is expressed in polar coordinates as: r = r0 + acos nθ . This function enables a flexible and easy to control layout, which directly affects the antenna's response. The arguments of the function are specified based on a simple deterministic design rule and the outputs of a parametric study. The antenna covers the 3.1-11 GHz band and has an ultra-miniaturised size of 864 mm³ when realised on a RT/Duroid 6010LM substrate of 0.635 mm thickness. To add dual-notch characteristics to the proposed antenna, a complementary dual-band split ring resonator inclusion is etched on the antenna's patch near the feeding line. The inclusion is designed to operate at the two Wi-Fi and ISM frequency bands, 3.5 and 5.8 GHz, respectively. These centre band frequencies are determined using a new hybrid method that utilises the resonant and non-resonant design approaches of metamaterial structures. Simulated and measured return loss values, radiation patterns and gain values for the proposed antennas (with and without notching) are in very good agreements, and demonstrate satisfactory performance. [ABSTRACT FROM AUTHOR]

A compact coplanar waveguide (CPW) fed frequency reconfigurable bow-tie microstrip antenna is proposed and experimentally verified which can be tuned at different bands between 1.94 and 3.27 GHz in single-band and dual-band modes. Two slots are carefully introduced on the ground plane of the antenna where two active varactor diodes are placed to vary its fundamental mode of radiation by variation of capacitance. To validate the antenna design, a fully functional prototype is fabricated and measured which ensures that the device can be operated at different frequencies of 2.02, 2.19 and 2.37 GHz with 35.9, 30.8 and 24.6% of impedance bandwidth, respectively, in the single-band mode. In dual-band reconfigurability mode, the resonant frequency of the antenna can be varied at 2.08, 2.17 and 2.3 GHz with a higher mode band within 2.7 and 3.3 GHz. The antenna shows maximum gain of 1.33 dB with 96.9% efficiency and 1.5 dB with 95.4% efficiency for single-band and dual-band reconfigurability mode, respectively. More importantly, the antenna has a compact dimension (0.31λ x 0.32λ x 0.0103λ at 1.94 GHz) and it produces symmetrical monopole type radiation pattern at all tunable bands. [ABSTRACT FROM AUTHOR]

In this study, a millimetre-wave (MMW) antenna is presented for the fifth-generation (5G) wireless multiple-input multiple-output (MIMO) applications, in order to offer numerous advantages including compactness, planar geometry, high bandwidth, and high gain performance. The concept of defected ground structures has been deployed for the first time in MIMO antenna design at MMW spectrum to fulfil 5G requirements of high bandwidth with compactness and low design complexity. The top surface of antenna comprises of a coplanar waveguide-fed T-shaped radiating patch element, while the bottom part is designed to constitute a partial ground loaded with two iterations of symmetrical split-ring slots at an optimised distance. Experimental results depict a wide bandwidth of 25.1–37.5 GHz, as well as a peak gain of 10.6 dBi at 36 GHz. Moreover, numerically evaluated efficiency of >80% is observed over the entire intended bandwidth of operation. For the demonstration, four-element MIMO antenna array of the proposed antenna element is also fabricated and tested, in order to validate high isolation between the adjacent elements, which makes the proposed antenna a potential candidate to be integrated in cellular phones and base stations for 5G MIMO systems and services. [ABSTRACT FROM AUTHOR]

Two bandpass filters (BPFs) are implemented on a single dual-mode square-shaped substrate-integrated waveguide (SIW) cavity with two etched coplanar waveguides. The proposed BPFs can achieve two transmission zeros (TZs) using dual modes in the SIW cavity (i.e. TE102 and TE201) with non-resonating mode (i.e. fundamental TE101), which provides a direct input-to-output coupling. Moreover, the positions of the two TZs can be tuned by changing the positions of input and output ports. Moreover, an extra TZ with controllable position is also achieved by using controllable electric and magnetic mixed coupling; and the TZ also can be split into two TZs for the mixed cross-coupling paths. The BPFs with the controllable TZs improve the selectivity and out-of-band rejection. The designed BPFs have a centre frequency of 5.8 GHz. The measured results agree with the simulated ones. [ABSTRACT FROM AUTHOR]

New generations of printed flexible antennas are playing an important role in wireless communication systems. The ultra wide band and wearable possibilities are critical aspects of these kinds of antennas. In this study, the proposed antenna is an elliptical monopole fed by a coplanar waveguide; it uses a kapton substrate and it is optimised to work from 1 to 8 GHz. In the case of copper, a conductive nanocomposite material based on a polymer (polyaniline: PANI) and charged by multiwalled carbon nanotubes (MWCNTs) is exploited. The flexibility of both the kapton substrate and the nanocomposite (PANI/MWCNTs) provides the ability to crumple the antenna paving the way to potential applications for body-worn wireless communications systems. In this study, the performance of the antenna is investigated in terms of return loss, radiation patterns and gain for both crumpled and uncrumpled antennas. The results confirm that performance remains at a good level when the antenna is crumpled. [ABSTRACT FROM AUTHOR]

This study presents a periodic defected ground structure (PDGS) to suppress the mutual coupling (MC) between coplanar antenna elements in a multiple-input and multiple-output (MIMO) communication system. The proposed PDGS consists of three defected ground structure units. They are etched away from the ground plane between antenna elements. The coupled polarisation transformer characteristic of the proposed PDGS is utilised to increase the antenna elements isolation. The increased coupled vertical linear polarisation component and decreased coupled horizontal linear polarisation component contribute to reduce the MC between antenna elements. By using this method, the authors achieve low MC level and better MIMO corresponding capacity. This method has little influence on the far-filed main radiation properties of the antenna elements. [ABSTRACT FROM AUTHOR]

Inkjet printing is a low-cost technique suitable to fabricate flexible electronic devices using solutions of conductive nanoparticles on any type of substrate without material waste as in conventional etching techniques. In this study, a low-profile wideband coplanar waveguide-fed monopole antenna operating at 20 GHz is designed and printed using silver nanoparticle ink on polyethylene terephthalate (PET) and on Epson paper substrates. The effects of varying the drop spacing (DS) of the ink on the conductivity of the printed films as well as on the antenna parameters were fully investigated by numerical simulations and by measurements. A conductivity of 1.8 × 107 Ω-1 m-1 was obtained for the films printed on PET using a DS of 30 μm leading to superior antenna performance with an achieved gain and antenna radiation efficiency of 1.67 dB and 96%, respectively. In addition, the size reduction reached 99%. On the other hand, antennas on Epson paper substrate show an. [ABSTRACT FROM AUTHOR]

A broadband circularly polarised antenna with a compact structure is proposed based on a microstrip-coplanar waveguide (CPW) fed rectangular slot antenna. The wideband feeding network power divider (PD) consists of a Wilkinson PD and a 90° phase difference comparator. The even modes of four CPW feed lines are generated to provide equal amplitudes but in phase quadrature. Circular polarisations can be excited over a very broad frequency band. A reflector is added to the antenna structure to improve the antenna gains. The inverted configuration, which places the reflector in the slot side, is ultilised to enhance the impedance matching. The measured impedance bandwidth for |S11| < -10 dB is 74.4%. A broad 3-dB axial ratio bandwidth of 70.8% is also obtained. The measured 3-dB gain bandwidth is 53.65% with the peak gain of 7.4 dBic. [ABSTRACT FROM AUTHOR]

In this study, the dual-reverse-arrow fractal (DRAF) geometry is applied to the sides of a slotted microstrip triangular patch to design ultra-wideband (UWB) antenna with a coplanar waveguide (CPW) feed with and without notch bands. It is shown that the proposed DRAF geometry has the capability of both reducing the antenna size, but without decreasing its bandwidth and also maintaining the other antenna radiation characteristics. It is shown that the antenna is miniaturised by 40% compared with the simple triangular patch. Furthermore, in order to prevent any interference of the proposed antenna with the wireless system of high performance radio LAN (HiperLAN)/2, a notch band is created by cutting two similar slots in the Tshaped CPW-feed. Such an antenna has applications in UWB systems. Two prototype DRAF antennas are fabricated and measured, which verify its desirable features. [ABSTRACT FROM AUTHOR]

A coplanar waveguide (CPW)-fed octagonal super-wideband fractal antenna is presented. It comprises four iterations of an octagonal slot-loaded octagonal radiating patch, CPW feedline, and modified ground plane loaded with a pair of rectangular notches. An impedance bandwidth of 3.8-68 GHz (179%) - i.e. a17.89:1 ratio bandwidth - is achieved. Desirable radiation performance characteristics, including relatively stable and omnidirectional radiation patterns, are obtained over this range. The experimental and simulation results are found to be in good agreement. The designed antenna has the advantages of wider bandwidth and miniaturised size over the previously reported structures. [ABSTRACT FROM AUTHOR]

A new design of frequency reconfigurable planar coplanar waveguide-fed array antenna for multiband MIMO (multi-input-multi-output) applications is presented in this study. The proposed two elements MIMO array antenna consists of two identical basic reconfigurable antenna elements. Each basic antenna structure consists of two quarterwavelength resonators and is capable of operating in WLAN (wireless area network) and WiMAX frequency bands. The centre frequencies of the operating bands are controllable independently by tuning the length of the corresponding resonators. Employing switches on the proposed structure has led to three different switchable operations [WiMAX (3.36-3.7 GHz), WLAN (5-5.8 GHz) and WiMAX and WLAN (3.17-3.77 and 5.13-5.88 GHz) simultaneously]. Moreover, by arranging the antenna elements in an orthogonal alignment in space and using polarisation diversity technique, the multipath performance of the presented MIMO antenna is improved. The fabricated reconfigurable MIMO antenna has a compact size of 48.5 × 25 mm2 while having more than 16 dB isolation level between its ports for all its various switchable performances. The measured results reveal that the proposed antenna can be a good candidate for modern multiband MIMO applications. [ABSTRACT FROM AUTHOR]

A new design concept of a multi-configuration antenna providing both frequency notched ultra-wideband and multiple narrowband functionality from a coplanar waveguide fed circular monopole antenna is presented in this study. The proposed multiple antenna configurations are achieved by loading the feed section of the antenna with circular split ring resonator pair of varying dimensions and inner ring orientations and shorting copper strips. Fabricated prototypes were measured and compared with simulation and good agreement is obtained for both impedance and radiation characteristics. [ABSTRACT FROM AUTHOR]

The theoretical study and experimental results of a compact tunable left-handed (LH) zeroth order metamaterial ferrite resonator is presented. The resonator has been designed and realised using a LH coplanar waveguide transmission line on a ferrite substrate. The theoretical analysis of the operation principles of the resonator has been provided. The detailed measurement setup and experimental results are discussed. The resonator is only 0.19 λg (65% reduced in size comparing with conventional one) at 4 GHz. The resonator has fractional bandwidth of 0.1% and average insertion loss, approximately 4.5 dB. Moreover, the zeroth order metamaterial ferrite resonator has tuning capability and requires lower DC magnetic bias. [ABSTRACT FROM AUTHOR]

A low profile (height = 3 mm) and wideband dual coplanar feed planar inverted-F antenna (PIFA) is proposed for diversity applications over the frequency range of 2.35–3.25 GHz with a fractional bandwidth of 32%. It covers LTE bands 7, 38, 40, 41 and WiFi frequency bands. The design is based on a comparative study on the mutual coupling between different feed arrangements such as the parallel feed, coplanar feed and orthogonal feed. The results show that the coplanar feed arrangement exhibits a lower mutual coupling level. As a result, the coplanar feed is employed in the proposed antenna and the polarisation diversity is achieved by exciting two orthogonal radiation modes; the antenna fed by Feed 1 uses open ground plane slot in the horizontal plane, while the antenna fed by Feed 2 is linked to PIFA. The modified top plate provides a self-matching circuit for Feed 2. The isolation between the feeds is achieved by an L-shaped ground plane slot. Both simulated and measured results are obtained, and the results demonstrate that the proposed antenna is a very good candidate for mobile diversity and multiple-input and multiple-output applications. [ABSTRACT FROM AUTHOR]

A highly reliable small-signal parameter extraction method for parasitic elements of the 0.1-µm GaAs metamorphic high electron mobility transistors is presented. De-embedding scheme for the coplanar waveguide (CPW) feeding structure is utilised in this method in a frequency range of 0.5–110 GHz with an enhancement approach to the correction of source inductance parameter sensitivity derived from oscillating measurements. The parasitic extrinsic capacitances are determined by modelling an Π equivalent circuit including the interaction between the sub-model and the CPW feedings. From this method, the authors achieved the most accurate parameter prediction with an effective fitting error of 10.83% among the small-signal models reported to date. [ABSTRACT FROM AUTHOR]

In this study, a new compact coplanar waveguide-fed wideband circularly polarised slot antenna is designed and fabricated. To achieve circular polarisation, the slot in the ground plane is truncated at one corner and excited by a modified L-shaped radiating element. To achieve wide axial ratio bandwidth (ARBW), one end of the L-shaped patch is connected with the ground via a slit. The ARBW is further improved by properly placing two additional narrow slots in the ground plane. The measured impedance bandwidth and ARBW at boresight are achieved 87.2% (from 2.2 to 5.6 GHz) and 81.05% (from 2.2 to 5.2 GHz), respectively. For the better understanding, the surface current distribution and parametric studies are presented. To characterise the antenna in the time domain, group delay and system fidelity factor (SFF) are measured. The measured group delay has less variation (of 0.5 ns) in the operating band and the measured SFF is found to be 0.89. The measured and simulated results are in good agreement. [ABSTRACT FROM AUTHOR]

A novel miniaturised design of broadband circularly polarised (CP) antenna using a coplanar waveguide feed is presented. To realise CP characteristic, a pair of inverted-L strips around two opposite corners of the slot is protruded. By properly folding the modified ground plane, the 3-dB axial-ratio (AR) band is shifted to around a lower-frequency location, whereas the input impedance band is shifted downwards through the Y-shaped loading strip. The overall size of the antenna is about 0.34 λ0 × 0.34 λ0 × 0.009 λ0 at 1.7 GHz. Measured results show that the proposed design can deliver 3-dB AR bandwidth of 36.8% (1.55-2.25 GHz) and 10 dB impedance bandwidth of 63.2% (1.17-2.25 GHz). [ABSTRACT FROM AUTHOR]