In this study, a novel compact radio frequency identification (RFID) tag antenna with a combination of a dipole and the double-layer symmetric electromagnetic band gap (DLS-EBG) structure is proposed for metallic objects in ultra-high-frequency (UHF) band. The DLS-EBG unit cell consists of a symmetrical double-layer structure and offset vias for tag miniaturisation. The equivalent circuit model of

Differentially fed six-beam switchable reconfigurable antenna is proposed in this study. The antenna consists of radiators, parasitic elements, cross-shaped feeding network and the ground plane. The radiators are formed by two pairs of gear-shaped cross dipoles. By changing the excitation differential ports to drive one of two pairs of dipoles, and by enabling different reflectors, the beam can be

The coaxial slotted-cavity antenna is an easily-manufactured, novel high-power microwave antenna developed specifically for its compact and shaped-beam characteristics. It can directly cascade with the high-power microwave source, and radiate linear-polarisation electromagnetic wave without extra power dividers and mode converters, which obtains a low profile. In this study, a double-layer coaxial

A compact single layer frequency reconfigurable Yagi-like multiple-input multiple-output (MIMO) antenna system is presented based on a half-ring closed loop slot excitation. The traditional omnidirectional pattern of a slot antenna is made directional by using a single slot-based complementary wideband reflector (CWBR) element. The proposed CWBR is compact in size, simple in construction, and is based

In this study, a multi-functional sandwich structure is proposed with mechanical support, electromagnetic radiation and absorption by radome-integrated design of metamaterial antenna array. The pyramid metamaterial absorber (PMA) is used as the radiator of the antenna element, with a fibre-reinforced resin composite radome attached on the top. To enhance mechanical strength of the radome and meanwhile

In this study, the authors present two new proposals for representation by the equivalent circuit model for aperture-type circular ring geometries, not yet studied in the literature. The study consists of the frequency response representation of frequency selective surfaces (FSSs) formed by circular ring aperture and concentric circular ring apertures. At first, the authors performed an equivalent

Multistatic, radar-based, microwave breast cancer detection provides more information in a shorter period of time than the monostatic approach. However, artefact removal is harder in the multistatic case due to antenna coupling. In this study, a multi-step imaging system is proposed for the multistatic approach. The first step is responsible for artefact removal, and it includes signals grouping, windowing

This work introduces a novel design for high efficiency and compact size dual-frequency wireless power transfer (DF-WPT) systems. The proposed design is composed of two identical transmitting (Tx) and receiving (Rx) substrates. Each substrate has a microstrip feed line, a C-shaped coupled resonator on the top layer and a spiral coupled defected ground structure on the bottom layer. The system is analysed

A novel low-profile substrate integrated waveguide (SIW) cavity-backed slot antenna with an enhanced gain is proposed. By etching four parallel transverse slots at the edges of the hexagonal SIW cavity as the radiating elements, higher resonance mode of quasi-TM 310 can be excited to achieve gain enhancement. A fabricated prototype with a size of 1.3 λ 0 × 1.3 λ 0 × 0.025 λ 0 has been measured. Results

An ultra-high frequency (UHF) travelling wave antenna based on complementary split ring resonator (CSRR) element is investigated in this study for pure near-field radio frequency identification (RFID) system. The proposed antenna consists of a T-type power divider, phase shifter, two microstrip transmission lines ended with two resistors and the metal ground loaded CSRR elements. The CSRR elements

A dual-band dual-polarised antenna for on-/off-body wireless body area network (WBAN) applications is presented, operating at Industrial, Scientific, and Medical bands of 2.45 GHz with circular polarisation and 5.8 GHz with vertical polarisation. The TM 11 mode is used for the off-body mode in the first band because of its broadside radiation pattern, meanwhile, the TM 02 mode is chosen for on-body

In this study, the authors propose a new numerically stable digital predistorter for the linearisation of RF Power amplifiers. The proposed predistorter is based on the parameterised Gegenbauer polynomials that can be optimised for maximum predistorter efficiency and stability under different input signal distributions. The robustness and the efficiency of the proposed predistorter are experimentally

One patch antenna with dual-band dual-mode (DMDB) characteristic based on mushroom structure is designed and analysed in this study. The antenna operates at two modes: the bidirectional mode with endfire radiation patterns and the directional mode with broadside radiation patterns. The equivalent circuit, dispersion diagrams, field distributions, reflection coefficients and radiation patterns are given

The design and analysis of a compact dual-wideband multi-mode resonant printed quasi-Yagi antenna with dual-driven element is presented. In the design, an orthogonal dual-bowtie dipole is applied as the driven element to achieve the dual-band characteristic with minimal size. The dual-bowtie dipole is designed to operate in the multi-mode resonance to expand its bandwidth. The structure is 60% smaller

Enhancing the horizontal gain of the omnidirectional patch antenna is always a problem with great difficulty. Inspired by near-zero-index metamaterial (NZIM) cover that can improve the vertical gain of a directional patch antenna, the authors designed two kinds of NZIMs that are placed above the broadband omnidirectional antenna to enhance the horizontal gain. Simulated and measured results indicate

A ten-element multi-antenna terminal for massive multiple-input–multiple-output (MIMO) in the fifth-generation (5G) sub-6 GHz with wide impedance bandwidth (IBW) is proposed. A grounded coplanar waveguide is employed to feed an inverted-F stub coupled to a hybrid loop antenna element. Through tuning, the multiple resonant modes are combined so that a wide IBW is achieved. Antenna element sites are

Α feasibility study of using components such as conductive Velcro tape and zip fastener to change the polarisation of a textile patch antenna from linear (LP) to circular (CP) is presented. The antennas are designed to operate at 2.3–2.5 GHz frequency band, are made using felt substrate and conductive cloth and their size is 100.4 mm × 74.2 mm × 4.26 mm. It is proved, via simulations and measurements

This study presents a systematic parameter study on orbital angular momentum (OAM)-based communication between antenna arrays. The recently proposed mixed-mode matrix representation is applied for investigating the dependencies of OAM-based communication on array configuration parameters. It is demonstrated that the performance of multi-phased systems including the OAM-based array is optimised in terms

A new multiple-input/multiple-output (MIMO) antenna design is introduced for future smartphones. The proposed design contains four pairs of double-fed circular-ring resonators located at different edges of the smartphone printed circuit board (PCB) with an FR-4 substrate and a dimension of 75 × 150 mm 2 . The antenna elements are fed by 50-Ohm microstrip-lines and provide polarisation and radiation

A new configuration of a Printed Quasi-Yagi Antenna (PQYA) with monopole elements has been proposed for broadband operation, in this study. This three elements printed Yagi antenna consists of a fed monopole on one side of the dielectric substrate, whereas, the parasitic elements of a reflector and a director are on the other side on the ground plane. The presence of the ground plane effectively makes

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

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 0.042 λ o at the resonating frequency. To verify the simulation results, the prototype of the proposed superstrate and antenna is fabricated and

A tightly coupled bowtie array antenna at a millimetre-wave band is presented in the study. The antenna has a simple structure and exhibits a high performance over an ultra-wide bandwidth. The feeding network is designed by using the dielectric-based inverted microstrip gap waveguide technology in order to have a compact layout. An 8 × 8 planar array is designed and prototyped. The measured results

This study presents the design of an efficient, moderately high gain and portable antenna operating at 58.27 MHz. The proposed antenna is a multilayered hemi-cylindrical shaped structure, which works on the principle of resonant inductive coupling using a multi-turn loop. An equivalent circuit, which takes into account the near field coupling effects, is also developed. The proposed antenna is electrically

A novel miniaturised wideband antenna based on dual-layer metasurface (MS) is proposed in this study. It is composed of three metallic and two substrate layers. The top metallic layer is the MS whose unit is a square patch etched four interlaced quarter arc-shaped slots (PQAS). The middle metallic layer is a circular ring patch. The bottom metallic layer is the MS formed by the square metal ring (SMR)

In this study, the authors present a beam scanning lens antenna for 30 GHz applications, which is composed of a feed horn and a planar lens with parabolic phase distribution. Due to the parabolic phase compensation, the lens antenna can perform the scanning coverage of ±60° with a gain tolerance of 3 dB. The fabricated lens has a size of 10λ 0 × λ 0 × 0.2 λ 0 ( λ 0 is wavelength at the centre frequency

A simple method to achieve multi-focus and pattern manipulation in antenna near field (NF) is proposed in this study, whose effectiveness is then validated by measurements based on different transmit-array antennas. The radiating aperture is divided into several regions and each region corresponds to one assigned focal point, thus achieving multi-focusing performance. Then, the superposition principle

This study addresses a negative group delay (NGD) circuit theory regarding a distributed passive topology consisted of an open-ended radial stub. The equivalent circuit composed of the lumped R, L and C elements is proposed. Then, the S -parameter model of the passive topology is established. The NGD analysis is described from the S -parameter model. The synthesis method enabling to determine the stub

An unbalanced microstrip bandpass filter (BPF) in dual-extended doublet topology with source-load (S-L) coupling is first presented and researched based on dual-layer capacitive-loaded dual-mode loop resonators. The input and output ports are located on the upper substrate layer. The lower dual-mode loop resonator is coupled to the upper loop resonator using four coupling apertures in the middle metal

In this work, a 2-layer frequency reconfigurable Yagi-like multiple-input–multiple-output (MIMO) antenna system is proposed based on a closed pentagonal slot-loop excitation. The MIMO system consists of 4 identical active antenna elements reactively loaded with varactor diodes to achieve frequency reconfigurability over a band from 1.5 to 2.1 GHz. The distinguishing feature of the proposed work is

In recent years, the characteristic basis function method has been developed as an efficient approach for the solution of large electromagnetic radiation or scattering problems. According to this technique, the currents over the scenario under analysis are defined using a set of pre-computed characteristic basis functions, associated with a number of blocks into which the geometry is partitioned. This

The use of orbital angular momentum (OAM) modes in radio communication is thought to enhance capacity. This work focuses on using the l = +1 mode transmitted from a 180 mm diameter, 8-element circular antenna array. The transmitted OAM beam was collimated by using a spherical mirror and the intensity and phase were investigated. A xyz scanning stage was used to profile the propagating OAM beam in three

Large array antennas are often assembled with several subarrays, and assembling errors containing position and orientation are the key factors determining the final radiation pattern. As an important feature of radiation patterns, the antenna gain significantly influences the design of the antenna. However, little research has been conducted on the accurate prediction and detailed compensation of gain

In this study, an ultra-compact meandered grounding resonator is proposed to design two millimetre wave bandpass filters (BPFs) in a standard 0.13-µm silicon-germanium (Bi)-complementary metal oxide semiconductor (CMOS) technology. The fundamental second-order prototype, namely BPF-I, consists of a pair of proposed resonators and a pair of grounded metal-insulator-metal (MIM) capacitors. To better

In this paper, a wide band ridge gap waveguide (RGW) fan beam antenna with low side lobe level (SLL) is presented making use of parabolic offset reflector concept in antenna geometry. In the proposed topology, in contrast to TEM based RGW horn, the amplitude distribution across the antenna aperture can be easily controlled. Furthermore, thanks to intrinsic feature of parabolic reflector in generating

Synthesis of planar continuous current sources (planar CCSs) with arbitrary shapes is developed for the generation of specified radiation patterns by method of moments (MoM) and method of least squares (MLS). First, an integral equation is expressed, which relates planar CCS current distribution to its radiation pattern. Second, the planar CCS region is divided into several segments and its current

A low-profile microstrip patch antenna (MPA) with wide bandwidth, wide beamwidth, and reduced cross-polarisation is proposed here. Firstly, the far-zone radiated fields of the MPA are deeply studied to improve its radiation performance. It demonstrates that the E -plane half-power beamwidth (HPBW) of the antenna could be progressively widened by using a single equivalent slot instead of two equivalent

An analogue modulation-type independent feed-forward carrier recovery approach for broadband wireless communication systems is introduced in this work. The focus is on the deliberately increased local oscillator (LO) signal feed-through to the radio frequency (RF) port of the up-converter in a direct conversion transmitter (TX). The strong LO feed-through is used at the receiver (RX) side to demodulate

A design methodology for a small-size multifunctional quad-band bandpass filter (BPF) exhibiting high selectivity is proposed in this study. In this design, the resulting BPF would comprise a dual-band split-type BPF, wideband BPF and narrowband BPF, and it can execute narrowband/wideband operation and provide close/wideband spacing. Since each passband can be formed by respective filters, the design

Four-way single-/dual-band operation integrated filtering power divider (FPD) with new design topology is presented in this study. For either single- or dual-passband response, it involves only one same-type pair of multi-mode resonators and three isolation resistors, comparing with other existing four-way FPDs. By adopting the even-/odd-mode analysis method to flexibly control the resonant modes of

In this study, the authors present three different metamaterial absorbers (MMAs) namely, T, split-I (SI) and split-Jerusalem cross (SJC) with different dimensions and geometrical configurations. The absorption rates of T-, SI- and SJC-shaped absorbers are studied at microwave frequencies. T-shaped absorber demonstrates perfect absorption at 10.19 GHz, making it suitable for single band operation, whereas

A new design of the double dielectric resonator antenna (DRA) fed by a printed ridge gap waveguide for beam-switching applications based on frequency selective surfaces (FSSs) is presented here. The dual-sided printed FSS element works in its reflection mode and comprises a slotted square C-shaped patch on the top layer and a square strip on the back plane. Therefore, the beam switching can be implemented

An efficient electronic beam steering technique in time modulated linear array (TMLA) is proposed, where the first positive and negative sidebands are utilised to implement the electronic steering process. In this technique, new periodic time sequences are used, in which a positive-ON, negative-ON, and OFF durations are utilised to obtain high sufficient steering in TMLA. Furthermore, it is shown that

The aim of this study is to disclose how the performance of a gallium nitride (GaN)-based X-band low-noise amplifier is modified by applying a blue-ray (404 nm) laser beam. The tested amplifier employs an aluminium gallium nitride/GaN (AlGaN/GaN) high electron mobility transistor on silicon carbide whose dc and noise behaviour have been first analysed with and without optical illumination. Mild improvement

In this study, a corrugated substrate-integrated waveguide (CSIW) is used to design a passive microwave displacement sensor. Hence, one of the electric walls of the proposed structure is formed by open-circuited quarter guided wavelength stubs and the other walls are made by metal vias and moveable copper metal is placed on the stubs. By displacing the moveable metal layer along with the stubs, the

In this study, dual-port dual-frequency tuneable MIMO planar inverted-F antenna (PIFA) is presented for mobile handheld device applications. The proposed MIMO antenna consists of two symmetrical PIFAs with the centre-to-centre distance of 43.0 mm (0.1906λ 0 ). The dual-band tunability is achieved by changing the capacitance (V 1 and V 2 ) of 4.15 pF (0 V)-0.72 pF (15 V). The impedance bandwidth of

The contribution of this study is to develop a miniaturised substrate integrated waveguide (SIW) cavity resonator with two evanescent-mode resonances. The circuit area of the developed dual-frequency SIW cavity is only 9.2% that of its conventional SIW cavity counterpart. A dual-band filter is implemented from using two miniaturised SIW cavity resonators. The two-passband frequencies can be independently

A dual-band rectangular dielectric resonator (DR) antenna is implemented with a multi-frequency circularly polarised (CP) response. The wide dual-band response is achieved by inserting the slots in the DR. The insertion of slots in the DR in a specific manner generates the orthogonal degenerate modes. Consequently, the multi-frequency CP response is obtained. The antenna provides the total overlapping

A generalised nested array (GNA) configuration with large minimum inter-element spacing is attractive to alleviate mutual coupling. In this study, by decomposing and rearranging the sub-arrays of GNA, the authors propose a new nested array configuration named as widened nested array (WNA). The WNA enables to provide the reduced mutual coupling, enhanced degrees of freedom (DOFs), extended array aperture

This study presents a compact transmission line topology to reduce the circuit size of single- and two-section branch line couplers (BLCs). The proposed transmission line is composed of a high impedance series line and one coupled line section. The coupled line section consists of two high impedance series lines and one coupled line. The proposed line is analysed with even-odd mode analysis to derive