A circularly polarised (CP) monopulse waveguide antenna array for Ka-band wireless communication is proposed. The antenna structure can be divided into six layers from top to bottom, including radiating layer, aperture layer, cavity layer, aperture layer, feeding layer and monopulse comparator. The upper radiating layer allows two transmission modes of the transverse electric (TE) wave and the transverse

This study presents a single-layer via-less antenna array operating in circular polarisation for wide-band operation in C -band. The antenna comprises disc based elements arranged in a sequential rotation architecture. Each element is tuned to exhibit multiple resonances with good circular polarisation performance over a broadband of frequencies. A proper feeding network is then designed so that the

The authors have proposed a dual-band reconfigurable Fabry–Pérot (F-P) cavity antenna with high gain and meanwhile small radar cross-sections (RCSs) in wideband. Different from the traditional F-P antennas, they used a dynamic metasurface reflective plane (DMRP) as the lower superstrate to realise reconfigurable functions and a digital coding metasurface as the upper superstrate to achieve wideband

A novel basic antenna element for travelling-wave substrate integrated waveguide (SIW) arrays is proposed in this study. The antenna element is based on a transverse slot and newly complemented by a pair of vias used for matching and a phase shifter. By changing the geometries of the slot and the phase shifter, the amplitude and phase of a radiated wave can be controlled. The proposed approach extends

An innovative design of a right hand circularly polarised (RHCP) antenna at two different resonant frequencies that is GPS (global positioning system) L2 and L5 has been proposed in this study. The proposed design comprised the concept of slotted radiator excited with a coaxial probe. Two asymmetric spiral slots were incorporated in a rectangular radiator to realise size miniaturisation, the axial

Low-profile and wideband gain enhancement Fabry–Perot cavity antennas (FPCA) is proposed using gradient Partially Reflective Surface (PRS) and gradient Artificial Magnetic Conductor (AMC). A wideband source antenna is designed with a −10 dB impedance bandwidth of 58.1% (6.1–11.1 GHz). The PRS is constructed by a complementary frequency-Selective Surfaces (FSS) with a square hole and four small patches

A new ultra-wideband millimetre-wave passive balanced duplexer (DUX), employing a lumped-element Wilkinson power divider and grounded-centre-tap transformer, has been developed using 0.18- m BiCMOS process for fifth generation operations at 28, 37, 39 GHz, and beyond. The developed DUX is configured single-ended transmitter (TX) and antenna (ANT) ports and differential receiver (RX) port. It has an

A K-band (18–27 GHz) dielectric-loaded waveguide antenna is designed as the feed for a parabolic reflector. The antenna is composed of a waveguide launcher and a dielectric load. The waveguide launcher is fabricated by selective laser melting using aluminium alloy. The dielectric load is fabricated by stereolithography using resin. The aperture field distribution of the antenna is tuned by extending

This study presents an ultra-wideband up-conversion mixer chip that operates within the frequency range of 2–12 GHz using TSMC 0.18 μm complementary metal oxide semiconductor (CMOS) technology. The architecture is based on that of a Gilbert cell mixer. The design of the transconductance stage is based on an inverting amplifier. Two series resonant inductors are used to increase the conversion gain

Although the ability of metasurfaces to control electromagnetic wavefronts has made it possible to design ultrathin carpet cloaks, the narrow operation bandwidth limits the performance of these cloaks. Here, the authors propose a new method to enhance operating bandwidth of metasurface-based carpet cloaks. The proposed cloak consists of super-cells providing appropriate phase shift to incident wave

This study presents a new reconfigurable quasi-elliptic filtering power divider (FPD) with tunable centre frequency (CF) and bandwidth (BW) by exploring singly one varactor-loaded triple-mode resonator. Avoiding the need for the variable couplings of the inter-resonant nodes and external input/output, the reconfigurability of the proposed FPD is achieved by only tuning the resonant nodes of the triple-mode

Processing conformal array signal is sensitive to antenna patterns on horizontal ( H ) and vertical ( V ) planes while mutual coupling (MC) impacts distinctly on them. Many existing MC calibration algorithms ignore that and thus lose their efficacy. In this study, MC is modelled as distortions of H and V patterns. The direction-dependent and slowly varied properties indicate that MC can be estimated

A periodic dielectric meta-surface structure was designed to extend the output window operating bandwidth of a wideband mode gyrotron travelling wave tube. The equivalent permittivity of the meta-surface matching layer can be adjusted arbitrarily by changing the lattice dimensions. The fabricated meta-surface dielectric window demonstrated a relative bandwidth of 53.9% with a reflection below in the

An electromagnetic bandgap (EBG)-inspired low-profile wideband textile antenna is presented. By partially surrounding a standard textile patch antenna with mushroom EBG cells, a significant enhancement of the 10 dB impedance bandwidth is obtained. In particular, whereas a standard textile patch antenna exhibits a typical 10 dB bandwidth of 6% for a substrate thickness of 0.04 , the proposed technique

Analysis of transient scattering from impedance surfaces using physical optics (PO) approximation is presented. Specifically, a fast relaxed vector fitting scheme is applied to determine a weighted rational function fit to the surface impedance and associated functions in the frequency domain, then inverse Fourier transformed to the time domain in terms of decaying exponential functions. The scattered

This work presents a new analytical transmission line model for microstrip T-resonator dielectric constant measurement method in order to simplify the extraction of the complex dielectric permittivity of the substrate and increase its accuracy. The proposed new formula, which is based on the T -matrix equivalent circuit of the structure, is only dependent on the propagation and attenuation constants

A two-port planar dual circularly polarised microstrip patch antenna is presented. The designed antenna has two groups of patches, each for transmission and reception. In one such group, only the central patch with truncated opposite corners is probe-fed whereas the surrounding patches act as parasitic patches for bandwidth and gain enhancement. A defected ground structure (DGS) consisting 4 units

In this study, a metamaterial (MTM)-based high-gain compact-wearable antenna for 2.45 GHz industrial, scientific and medical radio band application has been proposed. To achieve the flexibility of the antenna, textile material felt fabric has been chosen as the substrate of the antenna as well as MTM. An omega (Ω) like structure has been taken as MTM unit cell design. High value of permeability is

This study presents a design and fabrication methodology for industrial broadband high power amplifiers (HPAs). The proposed method considers design constraints for broadband HPAs and parasitic effects arising from the fabrication process. This method is based on power combining networks (PCNs) whose characteristics such as power handling constraints, insertion loss, and bandwidth depend on the employed

Metamaterial-based double-slit complementary split rectangular resonator sensor is proposed for the characterisation of dielectric properties of the materials under test (MUTs). The proposed sensor is designed and simulated on the CST microwave studio software using a low-cost substrate FR4. An array of three identical resonators is etched in the ground plane of the sensor to achieve a single and deep

A novel type of wide-band long-wire antenna is presented for 60 GHz wireless on-board chip-to-multi-chip applications using a vertically polarised electric field. The psi-shaped structure is devised to match the antenna input impedance to 50 Ω and to increase the front-to-back ratio by placing two bent 0.5 λ eff lines parallel to the original long-wire antenna, which resulted in improved realised gain

A dispersive delay structure (DDS) is a device that creates a specified group delay function over frequency bandwidth. In this study, the idea of trapping the electromagnetic waves in a feedback loop is proposed to achieve higher group delay swing. The proposed structure includes two transmission lines and two junctions that act as power divider/combiner. The transmission lines can be either dispersive

In this study, the authors present an electromagnetic model of a nanodipole array above a double-layer Graphene (DLG) operating at Terahertz. The graphene layers deposited between the dielectric mediums are modelled as surface impedances with conductivities described by the Kubo model. The electromagnetic fields are defined by the spectral representation of the periodic Green's function with impedance

This study presents a planar single-layer metasurface, with tri-band 10 dB radar cross-section (RCS) reduction under normal incidence for both polarisations, by employing optimised multi-element phase cancellation. The designed artificial magnetic conductor (AMC) unit cell is composed of an upper metal structure, a dielectric layer, and a bottom metal ground. When the dielectric constant and thickness

This study proposes a compact structure of the three-way Gysel power divider with arbitrary power dividing ratio, which has a significant difference from existing N -way ones with a common node in the centre of the circuit. First, existing equations are reviewed, and new analytical closed-form equations are derived according to the proposed structure. The frequency bandwidths, affected by the parameters

High data rate wireless links are an affordable and easily deployable solution to replace or complement fibre. The wide frequency band available at millimetre waves above 100 GHz can support multi-gigabit per second data rate. However, the high attenuation due to rain and humidity poses a substantial obstacle to long-range links. This study describes a wireless system being developed for point-to-point

An ultra-wideband phased array antenna using interconnected elements arranged in triangular lattices is investigated. The basic unit cell of the array is a dual orthogonal crossed ring structure. Each element is interconnected to its neighbour using capacitive loading. The ring structure on a planar surface produces broad frequency bandwidth with wide scan angles. Unlike other three-dimensional elements

The higher order resonances of microwave superconducting filters with spiral resonators were suppressed, giving a very wide stop-band. In one filter spirals were modified to have equal fundamental resonances, but different higher order resonances, by adding stubs and using non-uniform line width. The higher resonances were reduced to −39 dB, in a stop band up to 4.3 times the pass band centre. In another

Spectrum sensing is one of the most important tasks of cognitive radios (CRs) to detect idle bands for opportunistic access. In centralised cooperative sensing, CRs sense a target band and share sensing information via reporting channel with a fusion centre to decide whether the sensed band is vacant or not. This information can be raw data in soft decision fusion scheme or local decisions on the channel

A camouflage dual-polarised antenna for 5G pico-cell (PC) base stations is proposed in this study. The antenna offers good coverage for the 5G sub-6 GHz frequency band (3.3–3.8 GHz) with a reflection coefficient better than −15 dB and a port-to-port coupling less than −23 dB. The proposed antenna consists of two layers (a radiating layer and a feeding layer) separated by an air gap. The radiating layer

Vehicle-to-vulnerable-road-user (V2VRU) communications have the ability to provide of awareness to both vehicles and vulnerable road users to prevent accidents. An accurate V2VRU channel model in critical accident scenarios is essential to develop a reliable communications system. Therefore, extensive wideband single-input and single-output channel measurement campaigns at 5.2 GHz were carried out

The theoretical foundations of the near to far field transformation (NTFFT) techniques with spiral scannings have been properly applied to develop a non-redundant spherical spiral NTFFT which properly accounts for a mounting of a volumetric antenna under test (AUT) in an offset configuration, due to any practical constraints. Such an NTFFT, based on the non-redundant sampling representations of electromagnetic

This study proposes a new strategy of extracting parameters for tapped delay line (TDL) channel models from vehicle to infrastructure channel measurements. The proposed approach is based on an already existing method to derive parameters for a non-stationary model using first-order Markov chains. It will be shown that with the proposed method, the number of taps necessary to regenerate the delay spread

In a wireless communication system, the radio propagation channel is a complicated component to characterise. Channel sounding equipment thus has to meet specific criteria to extract the desired channel parameters. In this study, the authors outline the development and validation of a vector network analyser (VNA) based channel sounder for the frequency range from 1 to 50 GHz using radio-over-fibre

This study presents the design process and preliminary results of a 1.8-m reflectarray antenna able to generate a complete multi-spot coverage for transmission from a geostationary satellite operating in Ka-band (18.2–20.2 GHz). The reflectarray is designed using a newly validated method which makes it possible to generate four spaced beams per feed at different frequencies and polarisations. Two different

Automotive radar systems are indispensable for advanced driver assistance systems and traffic safety. Besides existing monostatic radar techniques, bi-static radar sensing like passive coherent location offers additional options to improve the radar visibility of vulnerable road users. Regarding the testing and evaluation of signal processing algorithms including parameter estimation, it is essential

One of the most popular localisation algorithms used in radio localisation systems is fingerprinting. The method has significant advantages: its implementation is easy and since it does not require any information on system infrastructure placement, it can be implemented in already deployed networks. However, it has a significant drawback, which is a high effort needed to create the radio map used

In this study, a series of time-varying breaking waves are generated by FLUENT. The backscattering normalised radar cross sections of the time-varying braking wave at different incidence angles are analysed by employing the method of moments. The scattering results can present the high polarisation ratios and sea spikes. In addition, the Doppler spectrums of the breaking waves are calculated for different

This study proposes an electrically thin frequency-selective surface-based microwave absorber without using resistive surface and lumped resistors to make it simple and inexpensive. The ground plane of the microstrip antenna (MSA) serves as the metallic back of the absorber. The top two layers of the proposed absorber are printed on both sides of the top FR4 sheet in a square annular ring form to encircle

A novel ring slot substrate-integrated waveguides (SIW) antenna is presented based on higher-order cylindrical cavity mode. First, TM 02 is used to realise a conical beam antenna. Electric field distribution on slot aperture generates four pairs of magnetic monopoles, each rotated 90° with respect to the centre of the cavity, resulting in a conical beam. By applying an offset to the feed point, the

A polarisation reconfigurable fractal slot antenna with dual-band performance is proposed in this study. The antenna consists of a Minkowski Island fractal inspired slot in the ground plane, which is excited by a microstrip line. The input match of the antenna is improved by placing two protruding horizontal stubs inside the two corners of the fractal slot. Four p-i-n diodes are placed within the grounded

A microwave planar log-periodic dipole array (LPDA) antenna embroidered on textiles is presented for the first time. This antenna gives a 3.33:1 impedance bandwidth with 5 dBi average gain across the 0.9–3   GHz band. This multi-layer textile antenna employs a new denim stack-up for repeatable measurements. The presented LPDA is tested under conformal conditions, with a demonstrated ability of frequency-dependent

The effect of using a non-uniform reactive impedance surface (RIS) on the circular polarisation performance of a planar antenna is investigated. It is shown that a very wide axial ratio (AR) bandwidth can be obtained, especially when the RIS is combined with parasitic strips. This result is only possible, thanks to the fact that the RIS is non-uniform. The technique is demonstrated by designing, building

This study presents a circularly polarised (CP) antenna with a wideband characteristic, which is caused by the interelement mutual coupling effect. The proposed antenna consists of a dipole array with four elements in centre symmetry and a wideband feed network. In order to extend the lowest working frequency, a strong mutual coupling effect is introduced to the adjacent co-polarisation elements. What's

Two sets of irregularly placed dielectric nano-spheres are synthesised as two nano-antennas. One of them has an end-fire and the other has a pencil-beam far-field radiation pattern. The electrical sizes (radiuses) and relative permittivities of all spheres are chosen to be 0.1 and 4, respectively. An incident plane-wave is illuminated on spheres. The aim is to find the optimal positions of spheres

Radiation field of conformal arrays can be obtained by simulation computation. There must be a trade-off between computation accuracy and complexity. With respect to applications where both high efficiency or even real-time applications and accuracy are required, such as adaptive beamformers together with time-varying array structures due to deformations or vibrations, more effective methodologies

Millimetre-wave (mmWave) frequency bands are expected to be used for future fifth generation networks due to the availability of a large unused spectrum. However, the attenuation at mmWave frequencies is high. To resolve this issue, the utilisation of high gain antennas and beamforming mechanisms are widely investigated in the literature. In this work, the authors considered mmWave end-to-end propagation

A wideband slot array antenna fed by perfect magnetic conductor (PMC) packaged microstrip lines at 28 GHz frequency range is presented. The slot array is designed with conventional microstrip technology and a PMC layer is used as a packaging solution to stop surface waves, cavity modes or any unwanted field leakage, coupling or radiation from the feeding lines. The PMC is implemented with a periodic

In this study, a robust and effective preconditioner for the fast method of moments-based hierarchal electric field integral equation solver is proposed using symmetric near-field Schur's complement method. In this preconditioner, near-field blocks are scaled to a diagonal block matrix and these near-field blocks are replaced with the scaled diagonal block matrix which reduces the near-field storage

A liquid crystal (LC)-based three-element microstrip parasitic array with beam switching is presented in this study. To understand the beam switching mechanism, a simple theoretical model of three-element Yagi antenna on the ground is given and analysed. In the proposed microstrip parasitic array, LC permittivities under three elements can be adjusted by bias voltages to control their resonant electrical

Metallic metacubes formed of six metal plate faces connected via a metal jack are shown to backscatter microwave radiation extremely powerfully. Experimental radar scattering cross-section (RCS) data from three-dimensional (3D) printed samples agrees very well with numerical model predictions, showing a monostatic RCS of 15 times the geometric cross-section. The principal resonance of the metacubes

In this paper, new designs of optically transparent wearable antennas have been presented. The explored antennas have the excellent features of high flexibility, small size, low specific absorption rate (SAR) and high optical transparency. The proposed antennas are realised by utilising highly flexible, optically transparent and low-cost materials. For achieving compactness in antenna dimension and

The inverse diffraction problem is considered for a layered dielectric plate in a metal waveguide of arbitrary cross-section. The proposed solution is based on the Cauchy problem for the Riccati equation. Based on this solution, algorithm and code are developed for the dielectric permittivity profile reconstruction. The measured and mathematically simulated values of the complex reflection coefficient

A novel low-cost, millimetre-wave antenna has been presented in this communication. The proposed antenna is a proximity-coupled linear array with coupled feedlines to achieve wideband characteristics. Good agreement between simulated and measured results is achieved and proves that the proposed antenna structure is capable of attaining over twice the bandwidth with the coupled lines than that attained

This study describes a light-weight wideband spiral antenna that radiates a unidirectional beam. To realise a light-weight antenna, a one-layer thick high-impedance surface reflector (HISR) for a reference spiral antenna is replaced by a two-layer circular HISR (TL-CirHISR). The TL-CirHISR is made of fan-shaped patches printed on a dielectric substrate. It is revealed that a voltage standing wave ratio

This study presents a beam-steerable antenna system that uses two mechanically-rotatable, phase-shifting surfaces (PSSs) functioning like a pair of Risley prisms for beam scanning operation at X-band. One of the PSSs also acts as a lens, performing beam collimation in addition to providing a phase shift gradient. Unit cells constituting the two PSSs were co-designed to determine the distance between

A frequency-domain approach for phase noise analysis of integer-N multiplier-type phase-locked loops (PLLs), based on the conversion matrix approach, is introduced that can take all non-linearities in the loop into account. It can also characterise all kinds of power spectral densities and correlation between variables and all aspects of phase noise-to-phase noise or amplitude noise-to-phase noise

In recent years, the microwave processes in artificial multiferroic media such as electromagnonic crystals have attracted increased research interest due to their potential applications for voltage-controlled spintronic devices. In contrast to the conventional magnonic crystals, the artificially created periodic structures are characterised by electrically and magnetically tunable band gaps in the

This work presents a new technique for the geometrical optics (GO) shaping of axisymmetric dual-reflector antennas. Both reflectors' generatrices are shaped by the continuous concatenation of conic sections, suited to provide simultaneous control of amplitude and phase of the aperture's GO field. With amplitude and phase control of the aperture field, the antenna designer has more options to achieve

A chipless radio frequency identification (RFID) system based on multi-resonant-based chipless RFID tags and fractional Fourier transform (FrFT) was simulated. Each tag codes a 3-bit unique identification (ID) in the form of a spectral signature in the interrogation signal. The signal is then backscattered to the processing unit (PU) for ID decoding. The simulated system accounts for two tags, 1 m