A wideband patch array antenna with dual sense circular polarization (CP) is investigated in this paper. Four rotated hexagonal patches are sequentially distributed on the upper surface of substrate 1 to form a patch array. In order to widen impedance bandwidth, an annular feeding network with four rectangular branches is designed. At the bottom of the antenna, two orthogonally placed microstrip baluns are introduced to obtain the characteristics of left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP). Meanwhile, four coaxial probes, passing through substrate 2 and substrate 3, are used to transmit the feeding signal between microstrip balun and the annual feeding network. The proposed patch array antenna is fabricated for verifying the feature of wideband and dual circular polarizations. The measured results show that the antenna has an impedance bandwidths of 70.2% (1.72-3.58 GHz) with an axial ratio (AR) bandwidth of 61% (1.85-3.48 GHz) and over 6.2 dBi gain at two ports. Moreover, the measured port isolation remains below -15 dB over the entire impedance bandwidth, and the measured radiation patterns with excellent directionality and symmetry at two ports indicate that the proposed antenna can be used for wireless applications.

Circular polarization is manifested by means of truncations on basic circular radiating patch with precisely designed asymmetric feed. The proposed truncated circular microstrip antenna (TCMA) yields impedance bandwidth (IBW) of 7.6 GHz, almost covering the FCC approved ultra wideband (UWB) frequency and 3-dB axial ratio bandwidth (ARBW) of 5.05 GHz spreading over two bands, enabling the antenna to be used for multiple applications in ultra wideband frequency range. A peak gain of 5.73 dBi is documented at 5 GHz which is within the circular polarization (CP) band. This single feed antenna is very simple to design and compact in size.

In this paper, an inkjet printed slotted disc monopole antenna is designed, printed and analyzed at 2.45 GHz ISM band on a polyethylene terephthalate (PET) substrate for early detection of brain stroke. PET is used as a substrate due to its low loss tangent, flexible, and moisture-resistant properties. By the implementation of slotting method, the size of this antenna is reduced to 40×38 mm². The printed antenna exhibits 480 MHz (19.55%) bandwidth ranging from 2.25 GHz to 2.73 GHz frequency. It shows a radiation efficiency of 99% with a realized gain of 2.78 dB at 2.45 GHz frequency. The Monostatic Radar (MR) approach is considered to detect brain stroke by analyzing the variations in reflected signals from the head model with and without stroke. The maximum specific absorption rate (SAR) distribution at 2.45 GHz frequency is calculated. The compact size and flexible properties make this monopole antenna suitable for early detection of brain stroke.

An effective and precise approach to the Wave Concept Iterative Process method modeling of magnetized graphene sheet as an anisotropic conductive surface is used to analyze the anisotropy of magnetostatically biased graphene and for studying an electrically doped magnetically biased graphene non-reciprocal antenna array for THz applications. The tuning of the performance of the array antenna is possible by varying the magnetic field and the chemical potential of graphene material. The return loss value decreases by increasing the magnetostatic bias and increases when the chemical potential increases.

This paper presents a miniaturized quintuple band antenna for multiband operation with the aim of developing a small and simple structure antenna that can operate at multiband frequency. The proposed antenna contains a rectangular microstrip patch, a transmission line with 50 Ω coplanar wave guide (CPW) and six L-slots. By introducing these L-slots along the X and Y axis, in the radiating element, the antenna yields five resonance modes at 2.4, 3.5, 4.4, 6.09, and 7.7 GHz while keeping the size of 27.4 x 24 mm². The prototype of the proposed antenna is constructed and experimentally studied. The measured and simulated results prove that the proposed multiband antenna is suitable for Bluetooth, WLAN, WIMAX, LTE, and X band applications. The antenna is designed using FR4 lossy substrate material with relative permittivity ε_r of 4.4 and thickness of 1.6 mm.

A coplanar waveguide (CPW)-fed flexible dual-band antenna using graphene as conducting material and Kapton polyimide as a substrate is proposed. The antenna shows increased impedance bandwidth due to the use of CPW-feed having the values of 80.29% (1.64-3.84 GHz) and 6.31% (5.52-5.88 GHz), respectively. The antenna has an overall size of 0.38λ × 0.43λ at center frequency of 3.4 GHz. The proposed flexible antenna has gain values of 1.82 dBi and 1.68 dBi with efficiency values more than 86% which makes the antenna commercially viable for smart wireless products having space constraints.

A compact microstrip fed dual polarized Ultra Wide Band (UWB) monopole Multiple Input Multiple Output (MIMO) antenna for access point application in Wireless Body Area Networks (WBAN) is proposed. The antenna is elliptically polarized in the 6 to 10.6 GHz band. The proposed structure possesses high isolation with the introduction of Modified Serpentine Structure (MSS) that behaves as a decoupling unit (DU). To further reduce the coupling and to improve the impedance bandwidth, an Electromagnetic Band Gap (EBG) structure is introduced. The proposed antenna has a wide impedance bandwidth with S₁₁ < -10 dB in the UWB from 3.1-10.6 GHz and has a high isolation S₂₁ < -25 dB. The antenna has a fractional bandwidth of 106%. The radiation pattern of the antenna is omnidirectional. The Envelope Correlation Coefficient (ECC) is equal to zero, and the capacity loss is 0.264 which proves the diversity characteristics of the proposed antenna.

Complex interconnection structure is a common structure on printed circuit board (PCB). Herein, the paper proposes a method of crosstalk cancellation point at the crosstalk problem between microstrip lines in a complex interconnection structure. First, a model of the coupled transmission lines-channel transmission matrix (CTL-CTM) of the complex interconnection structure is established. Second, the CTL-CTM is simplified through the equivalence of crosstalk-coupling coefficient of parallel coupling microstrip lines to that of the complex interconnection structure. The eigenvalue of the simplified CTL-CTM is then decomposed, based on which the construction of crosstalk cancellation circuit is performed. Simulation results show that the proposed method can effectively improve the quality of eye patterns on complex interconnection structures.

This paper presents an efficient method for evaluating the flux linkage between two circular loops located on the top surface of a plane multilayer soil. The method consists of a rigorous procedure, which leads to expressing the flux as a sum of products of Bessel functions. First, the integral representation for the mutual inductance is cast into a form where the integration range is continued to the negative real axis. Subsequently, the non-oscillating part of the integrand is replaced with a rational approximation, arising from using a well-known least squares-based fitting algorithm. Finally, analytical integration is performed by applying the theorem of residues. As a result of the proposed method, the flux linkage between the loops is expressed as a finite sum of products of Bessel functions. Since no assumptions are made in the mathematical derivation, the obtained explicit expression is valid regardless of the operating frequency. Numerical tests are performed to show the advantages of the proposed method with respect to standard numerical integration techniques. In particular, it is seen how the use of the derived series representation for the inductance with 50 terms permits to achieve the same accuracy as conventional Gauss-Kronrod numerical integration technique, with the advantage of reducing the computation time by at least 8 times.

A filtering rectangle dielectric resonator antenna (DRA) with high band-edge selectivity is proposed in this paper. The DRA is fed by a simple hybrid feeding structure consisting of a microstrip-coupled slot on the bottom and a thin metallic strip on the side of DRA to excite the fundamental TE^y_1δ1 mode. The feeding structure establishes a cross-coupled mechanism which includes electric and magnetic coupling; thus, introducing two radiation nulls at the band edge without any filtering circuits. By using the designed hybrid feeding structure, a bandpass filtering response is obtained. For enhancing band-edge selectivity, a shorted stub is introduced to weaken the coupling between the two microstrip stubs of the feeding structure. A wide impedance bandwidth of 19% and a flat gain of around 5.6 dBi are realized. To validate the design, a prototype is fabricated and measured, showing a favorable agreement with the simulated results.

In this article, we design a reconfigurable bandwidth based on a concentric ring slot antenna using graphene. The developed antenna has good agreement between simulated and experimental results. The use of graphene in Terahertz (THz) has shown better performance than metal, and the variation in the chemical potential of graphene provides excellent performance properties, good return loss reaching -33.288 dB, bandwidth reconfiguration from 255 GHz to 406 GHz, and a good gain. These results are promising for THz applications and particularly for the application of medical imaging. The modeling and validation are performed using the CST Simulator.

In this paper, a novel dielectric resonator antenna has been numerically simulated and experimentally demonstrated. The proposed design, comprising an Indium Tin Oxide (ITO) coated glass slide placed on a microstrip transmission line, is intended for WLAN and Wi-Max applications. The antenna shows a maximum bandwidth of 2.15-7.65 GHz and 10.36-11.78 GHz and a gain ranging from 2.21 to 6.44 dB. The novelty of the design lies in the use of ITO coating on glass to enhance as well as regulate the antenna bandwidth. Parametric variations have been investigated to analyse the topology for understanding the effect of the design parameters on gain, bandwidth, and reflection coefficient. A prototype has also been fabricated, where different ITO sheets have been mounted to measure the response. The proposed geometry has been found to be better and competent enough with respect to antenna parameters than existing Ultrawide Band antennas.

A wideband end fire antenna architecture in planar technology with fewer turns: helix antenna in planar technology adopting thickness of quarter wavelength is suggested. A wideband 24 GHz helix antenna with 2.25 turns in Rogers compressed RT 4350 technology is presented. The antenna has a bandwidth of 6.2 GHz for S₁₁, gain of 9.3 dBi, half power width of 39.5° and 39° respectively in X-Z and X-Y planes. This helix antenna is characterized by wide bandwidth, high gain, high half power width, compactness and high gain turn ratio. It could also be utilized in antenna design for other frequency bands with compressed PCB technology, as well for on-chip THz antenna design.

The proposed antenna structure is excited for multiple operational modes by means of meandered strips. The compact planar monopole antenna is demanded enormously for handheld devices especially automatic meter reading and tablet devices. Due to Chu limit, it is extremely vital to miniaturize an antenna by balancing tradeoff between bandwidth and radiation efficiency. The designed antenna is formed by two interconnected broad monopole open slots which covers multi-bands for smart energy meter and tablet computer applications. The cost effective FR4 laminate of size 50 x 200 mm² (0.4λ x 1.6λ) is employed to match standard tablet computer communication module dimensions. The impedance bandwidth, for all excited resonant modes, is above typical requirement of 2%, and the VSWR is well below the necessary requirement of 1.5. The peak gain ranges from 0.94 dBi to 1.92 dBi. Radiation patterns along with other antenna parameters are satisfactorily meeting the demand of Wireless Energy Meter and Tablet Devices. The effects of varying dimensions of a monopole on the radiation characteristics have also been presented. The return loss and radiation patterns computed through simulations are validated through experimental measurements in an anechoic chamber environment.

The problem of impedance synthesis of two-dimensional diffraction arrays of thin linear vibrators, whose geometric centers are located at the nodes of a flat rectangular grid with double periodicity is solved analytically. The problem is formulated as follows: the complex surface impedances of the vibrators should be determined which allows to steer the diffraction radiation maximum of the array to any predefined direction. The problem is solved under following assumptions: array is excited by a polarized plane wave, and the radiation pattern (RP) of each vibrator element in the array coincides with that of an isolated radiator. The correctness of the solution is verified by simulations using the formulas for the vibrator impedances for the 5 by 5 antenna array.

This paper describes the synthesis of a bandpass filter to achieve high selectivity and rejection properties using a new class of filter functions called chained-elliptic function filters. Chained-elliptic filters have higher selectivity than Chebyshev function filters and have the property of sensitivity to manufacturing tolerance reduction in chained-function filters. The proposed design has high selectivity and reduced sensitivity, enabling easier and faster filter fabrication. The characteristic polynomials of chained-elliptic function filters are derived through chaining elliptic filtering function and extracted to form a coupling matrix of the bandpass filter. The novel transfer polynomials are given in detail, and a thorough investigation of the filter characteristics is performed. A theoretical comparison with Chebyshev and elliptic filters of the same order is performed to ascertain the demonstrated advantages of this proposed filter class. A high frequency narrow-band fourth-order chained-elliptic function waveguide filter centred at 28 GHz with a fractional bandwidth of 1.61% is fabricated to validate the proposed design concept. A good match among the measured, simulated and ideal filter responses is shown where the overall responses between measurement and simulation have a difference of approximately 2% which is within the acceptable limit. The chained-elliptic function concept will be useful in designing low-cost high-performance microwave filters with various fabrication technologies for millimetre-wave applications.

In this paper, a graphene-based reflectarray antenna using ENZ (Epsilon-Near-Zero) metamaterial at terahertz (THz) band is proposed, and the performance of its unitcell is investigated. Then, the phase distribution and radiation pattern of the antenna are examined. Benefiting from exceptional complex surface conductivity of graphene which is a novel 2-d material, the size reduction of reflectarray has been facilitated as a result of plasmonic mode propagation within the structure which in turn leads to an increase in propagation constant. Moreover, tunneling phenomenon in ENZ material, a kind of metamaterial which has a relative permittivity under 1, helps reduce the loss. Taking advantage of these outstanding features of both materials, the proposed reflectarray is designed to function at 2.5 THz and is composed of 150×150 elements with square-shape configuration. We have achieved 40 dB of gain using the combination of graphene and ENZ material in reflectarrays, and also it is the first that time they are used together in the reflectarray. This work mainly focuses on the impact of using ENZ material and graphene simultaneously which is not done before, then the results demonstrate that it has a considerable effect on increasing the reflectarray gain.

In this paper, an eight-port antenna array operating in the 2.6 GHz band (2550-2650 MHz) for a multi-input multi-output (MIMO) mobile terminal is presented. The design is composed of four pairs of compact dual-polarized slot antennas that are symmetrically placed at the corners of a mobile-phone mainboard. Each antenna pair consists of miniaturized petal-shaped slot resonators fed by two independent microstrip-feeding lines, thus facilitating radiation pattern and polarization diversity: when acting together, they facilitate multi-channel MIMO operation. The design offers good isolation, dual polarization and full radiation coverage in a smartphone sized package. A low-cost FR-4 dielectric (ε = 4.4, δ = 0.02, and h = 0.8 mm) with a dimension of 75×150 mm² is used as the PCB substrate. The characteristics of the smartphone antenna are examined using both simulations and measurements.

This work reports the application of a microwave sensor in measuring human blood glucose concentration. The main contribution of this work lies on the blood glucose profile which is collected from 69 random patients regardless of their gender, age, and haematology properties, instead of using water as the base or focusing on a single person. Hence the blood glucose profile is more realistic. Blood is extracted from the participants and dropped at the center of the dumbbells section of a microstrip defected ground structure to gather the notch frequency shifting data. On the other hand, the blood samples are measured using Omron Freestyle Glucometer to collect their associated blood glucose readings. Five predicting models have been proposed in this work. Based on the cross-validation, it is found that the blood glucose level can be correlated very well with shifted notch frequency by using a linear model. It introduces least root mean square error (RMSE) of 0.0592 and shows good correlation (R² = 0.9356) between the reading from commercial glucometer and microwave sensor in the range up to 12 mmol/L. The reliability of this microwave sensor is proven once again when the predicted blood glucose data are all falling in Zone A of Clarke Error Grid. The outcome of this work shows the capability of this microwave sensor in measuring the blood glucose level. Since this microwave sensor can be reused under a proper cleaning procedure, it improves the sustainability of conventional blood glucose testing by reducing the disposal of testing strips and cost. It is believed that this sensor will be suitable for extensive blood glucose testing conducted in the laboratory.

This letter presents an approach to design a linear phase substrate integrated waveguide (SIW) bandpass filter with good selectivity. The topology of the proposed filter is implemented based on cross and bypass coupling schemes, which simultaneously introduce a linear phase response and good selectivity, respectively. According to the proposed topology, a multilayer SIW filter is presented to realize the two kinds of couplings and preserve a compact size. Then, the defected ground structure is adopted to further improve the out-of-band rejection. To demonstrate the proposed design method, one double-layered SIW bandpass filter is fabricated and measured. Measured results show that the proposed filter has a linear phase response and good out-of-band rejection, as well as a good agreement between simulated and measured results.