Wireless devices that can operate under harsh environments are of great interest for military, space, and commercial applications such as antennas and radomes for fighter jets, wireless sensor networks for oil drilling and aircraft propulsion, and safety devices for first responders. Since antennas are key components of Radio Frequency (RF) Systems, it is crucial to have the antenna be able to withstand the same environmental hardships for a reliable and efficient communication. Various substrates have been utilized to implement antennas to withstand harsh environments and particularly high temperatures. Existing solutions such as silicon carbide (SiC), alumina, and polymer derived ceramics require complex deposition and patterning techniques, which make them unsuitable for low-cost RF and microwave applications. The main objective of this study is to explore microstrip patch antenna fabrication technology utilizing Zirconia Ribbon Ceramic (ZRC) materials and assess ZRC as a potential dielectric substrate for harsh environment applications. To do so, first, a wideband coplanar waveguide (CPW) fed monopole antenna is presented on ZRC substrate operating within the S band. The proposed design has been manufactured using two separate methods including a clean room sputtering process and inkjet printing. A good agreement has been obtained between the measured results of the inkjet-printed prototype and simulations. Impedance matching and radiation patterns are investigated. The inkjet printing process has been shown to be a viable and cost-effective solution for fabricating ZRC-based patch antennas.

This article proposes a four-port multiple input multiple output (MIMO) ultra-wideband (UWB) antenna that operates across 3 to 13 GHz. Four identical fractal patches are placed orthogonally to each other. The uniqueness of the proposed design is that it does not need to incorporate any dedicated/specific design/component to realize notches within the UWB range. The elimination of notches, enhancement of bandwidth, and improvement of isolation have been achieved by integrating a resistance-loaded stub with the ground plane. The isolation between the elements was measured to be below -20 dB across the entire operating band. The fabricated prototype exhibits better diversity parameters like envelop correlation coefficient (ECC) < 0.003, diversity gain (DG) > 9.99, channel capacity loss (CCL) < 0.4 bps/Hz, and mean effective gain (MEG) < 2 dB. The proposed MIMO antenna shows omnidirectional radiation patterns with a peak gain of 5.4 dBi and radiation efficiency > 66% with required compactness having interelement (edge to edge) distance of 5.4 mm. After application of decoupling method radiation efficiency varies from 66% to 82% with gain ranging between 1.8 and 5.54 dBi. The diverse performance of the fabricated MIMO proves it to be a good candidate for UBW imaging, LTE applications, and S, C, and X band applications.

A narrowband, high selectivity Substrate Integrated Waveguide (SIW) bandpass filter with perturbing vias and CSRR is proposed for Sub-6 GHz applications. Firstly, the perturbing vias are positioned at the symmetrical axis of the SIW cavity which produces distinct electric field distribution for the first two modes. Next, the ground plane is engraved with the CSRR placed at an offset distance on either side of the perturbing vias, forming the coupling arrangement that combines mixed and magnetic, electric coupling. The presence of CSRRs resulted in a narrowband filter. The filter's center frequency is 4.947 GHz with a fractional bandwidth of 1.16%. By comparing the fabricated filter to an existing SIW conventional multi-cavity or cascaded resonator, a size reduction of 117% is achieved. The simulated and measured results agree with each other.

This paper presents the design methodology, simulation, and affordable implementation of a mobile digital satellite broadcasting receiver with 64 elements. The speed and range of electronic beamforming are also obtained. The proposed methodology including techniques and architecture are defined by concerning cost, commercial off-the-shelf and components, and avoidance of high-frequency circuit designs by Delay-line-PLL for phase shifting, instead of expensive RF phase shifters with complicated control buses. Choosing this architecture results in using available elements and home receivers for antenna implementation. The design results in 6-bit resolution phase shifters and ±16 degrees 2D half power electronic beam scanning range. For practical implementation feasibility, a prototype of the array is fabricated and tested, successfully. Obtaining the phase shifters' resolution and sampling of the array output power are also described. A simple and effective algorithm is proposed for grating lobes elimination, and SNR maximizing which performs the tracking task under the platform movement conditions.

Radio-frequency source localization becomes a major challenge for many applications such as beam-steering or MIMO communication. This task is commonly carried out by taking advantage of the adjustable radiation patterns of phased arrays to scan an area. Nevertheless, it can be difficult and expensive to implement in some frequency bands of the last generation of communication systems. Here, we propose an alternative based on a single port compact metamaterial antenna. We use a finite periodic array of sub-wavelength (λ/6) resonators for the design of this antenna. A microstrip line is added to excite the resonator array etched on a grounded low-loss substrate and to use it as a planar antenna. In such antenna system, the coupling between sub-wavelength resonators is able to induce a strong dispersion and leads to several complex radiation patterns over a specific narrow frequency band. We implement numerical methods to estimate the direction of a target antenna by taking benefits of the complex frequency signatures. We experimentally demonstrate that a single port sub-wavelength antenna made of a finite array of metamaterial resonators is able to retrieve the direction of a narrow band (3.6% relative bandwidth) emitting target around 5.5 GHz with a maximum precision of 3˚. Such a compact planar system (λ/3, λ/2 and 2λ/3) can be used to substitute the phased array localization technique in order to provide the necessary angular information in many applications such as mm-Wave communication and can be extended to high frequency regimes by using the corresponding resonators.

The present paper describes a substrate integrated waveguide (SIW) band pass filter with a T-shape slot on the upper layer, which exhibits a wide-band frequency response. The parameters of the filter are optimized by using Multi-Layer Perceptron artificial neural network (MLP-ANN) that uses Levenberg-Marquardt (LM) algorithm. A comparison is made between ANN optimized results and simulated results, and they result in minimum mean square error (MSE). A physical prototype is fabricated using printed circuit board (PCB) process, and measurements are conducted using the network analyzer. The measured results obtained agree well with the estimated ones. The filter shows a wide-band response with a transmission bandwidth of 8.96 GHz, ranging from 6.10 to 15.06 GHz with a fractional bandwidth of 81.4%. Furthermore, the insertion loss of the filter in the entire passband is varied from -0.4 dB to -0.2 dB, and the return loss is more than -10 dB.

A concept to minimize the volume of the classic bifocal elliptical lens antenna is proposed. By applying the image theory, a reflective ground plane is placed along the short axis of a bifocal elliptical lens. An antenna-on-chip (AoC), as the lens's feed source, is placed at the upper focus and packaged by the lens body. The AoC radiates toward the ground plane instead of the free space. The geometric optics (GO) ray tracing analysis shows that the optical path of the miniaturized monofocal integrated lens antenna (ILA) is equal to that of the classic bifocal ILAs, so the gain is almost unaffected on the basis of the lens' volume reduction. For the quantitative evaluation of the gain loss caused by feed occlusion, a set of analytical equations is given. To verify the design concept, a 26 GHz miniaturized self-packaged monofocal elliptical ILA is designed and fabricated by 3D printing technology. The ILA achieves a 26.5 dBi gain and a size reduction rate of 38% compared with the classic bifocal elliptical lens. Moreover, the ILA also functions as the package for the AoC's die. The proposed design concept can not only reduce the volume of the classic bifocal elliptical lens dramatically but can also save the effort and cost to package the AoC's die in a highly integrated system, which is believed to have great potential to create large profit margins for the fifth-generation (5G) mobile network applications.

In this paper, we propose a design methodology for waveguide applicators to maximize microwave power deposition into human tissues. The optimized applicators can be used in the experimental studies of the biological effects of exposure to electromagnetic radiation in the frequency range from 6 GHz to 100 GHz. The design methodology relies on the provision of reflectionless matching of a dissipative waveguide load, achieved by employing a matching network based on a quarter-wave transformer prototype. The prototype is synthesized by knowledge of the voltage standing wave ratio (VSWR) evaluated in the unmatched loaded waveguide. A key difference from the conventional synthesis procedure is that in our design approach, the characteristic impedance of the first transformer section is given, and we have to not only determine the characteristic impedances of the remaining sections, but also establish the output load. A solution of this synthesis problem and the process of converting the transformer prototype into a waveguide structure are described. The physical structure can be implemented according to provided sample models of waveguide WR137 applicators employing symmetric inductive or capacitive posts. The matched waveguide applicators are easy to manufacture, and according to the results from computational simulations, they demonstrate superior performance compared to the unmatched waveguides. Limitations of our designs (narrow bandwidth, dependence on the type of tissues encountered, limited potential for miniaturization) are discussed.

This paper presents the design and fabrication of a wideband circularly polarized CPW-fed compact diamond-shaped antenna. To enhance the wideband response and axial ratio in the desired frequency band, the geometry of the proposed antenna is modified. The modified antenna consists of one radiating element that includes two slits and one horizontal rectangular stub and an improved ground plane. The suggested wide-band antenna has overall measurements of 25 mm x 28 mm x 1.6 mm. The V-shaped slit generates two orthogonal modes in the proposed antenna to excite circular polarization. The rectangular stub improves the wideband response in 2.35-4.62 GHz. The fabricated prototype antenna demonstrates good consistency between simulation and measured results. The suggested antenna resonates over a 2700 MHz transmission bandwidth between 2.35 and 4.62 GHz, making it a good choice for WLAN and WiMAX applications. The average gain in the wideband is 3.1 dBi. It is shown that our suggested approach is a great choice for developing any wideband microstrip antenna for usage in a variety of wireless communication systems.

In this paper, a novel compact 4-port Vivaldi Multiple Input Multiple Output (MIMO) antenna is proposed for 5G wireless devices. The presented antenna has dimensions 40x40x1.6 mm³. The suggested antenna is fabricated on RT/Duroid dielectric material with dielectric constant of 2.2. The orthogonal arrangement of antenna elements and embedding slits between them result in enhanced isolation. The gain observed for the proposed antenna is 2.405 dB. The diversity performance of MIMO structure in terms of Envelop Correlation Coefficient (ECC < 0.02), Total Active Reflection Coefficient (TARC < -10 dB), Diversity Gain (DG > 9.998), Channel capacity Loss (CCL < 0.4) and Mean Effective Gain (MEG < 1 dB) is studied and analyzed. The simulated and measured results are in good agreement.

A polarization reconfigurable dielectric resonator Antenna (DRA) is proposed for X-band applications. The antenna provides circularly polarized (CP) or linearly polarized (LP) radiations at the same frequency band. Altering the states of two PIN diode switches offers a choice of one of three polarization options: (i) LP radiation; (ii) left-hand CP (LHCP) radiation; (iii) right-hand CP (RHCP) radiation. The simulations and measurements are in close agreement, indicating that the LHCP and RHCP radiations have reconfigurable polarization traits with a 21.3% impedance bandwidth ranging from 9.6 to 11.9 GHz and a 3.4% for the LP radiation that extends from 10.2 to 10.5 GHz. There is simultaneously a maximum gain of 6.9 dBic with a circa 4% axial ratio (AR) bandwidth for the LHCP and RHCP radiations.

In this paper, a new formula for calculating the self-inductance of a thin conical sheet inductor is given. The presented work is derived in a semi-analytical form based on the complete elliptic integrals of the first, second, and third kind plus a term to be solved numerically. The analytical formula is obtained in the special case when the thin conical sheet inductor is degenerated into a thin wall cylinder. The validation of the presented formulas is done by triple, double, single integration and by the semi-analytical formula. These self-inductance calculations of the thin conical sheet inductors can be especially useful in broadband RF applications and wireless power transfer systems where conical inductors have been used.

Synthetic aperture interferometric radiometer (SAIR) requires lots of antennas, receivers, and correlators to accurately reconstruct the brightness temperature (BT) distribution of the scene. Aiming to reduce the complexity of the hardware requirements in SAIR system while maintaining the image quality, a new optimal sparse reconstruction method is developed in this paper. Different from the existing imaging methods, the proposed method constructs the optimal receiving array with a few elements by evaluating the mutual coherence and the array factor of the sensing matrix in SAIR system, so as to achieve high-quality reconstruction of the BT image. Numerical simulations and experiments demonstrate that the proposed method can reconstruct the BT image by solely using a few receivers with higher image fidelity than the competing methods.

A W-band dual-circular-polarization (dual-CP) monopulse Cassegrain antenna for polarization detection of radar target is presented in this letter. The proposed antenna consists of a main reflector, a sub reflector, a dual-CP feed source based on the septum polarizer, and a comparator. Two orthogonal circular-polarized signals [left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP)] electromagnetic wave can be transmitted and received simultaneously by this antenna. The principle of the antenna is introduced and analyzed, and then a prototype of the antenna is simulated, fabricated, and measured. Measured results are in good agreement with the simulated ones. At 94 GHz, the gains of the LHCP and the RHCP sum beam (SUM beam) are 38.6 dBi and 38.8 dBi counting the insertion loss of the comparator, which indicates that the radiation efficiency is better than 44.2%. The 3-dB beamwidth is about 1.5° with a sidelobe level (SLL) of -16.6 dB, and the axial ratio is lower than 1.43. A null depth of -26 dB for the difference beam (DIFF beam) is observed, and the gain ratio between the LHCP monopulse beams is 5.9 dB. Measured results demonstrate that the proposed antenna is very applicable in the polarization detection of radar target at W-band.

A sensor to accurately predict chemical concentrations has been proposed in this research work. Inspired by Metamaterials, the sensor is composed of Complementary Split-Ring Resonators (CSRRs) and utilizes the Machine Learning technique to accurately predict the concentrations. The sensor is designed to maximize the interaction of the Material Under Test (MUT) with the sensitive regions of the CSRRs. The usage of costly and complex fluidic channels and sample containers is avoided by using filter paper for the liquid MUT placement in between the resonators. The proposed sensor is small (2.3 cm × 2.3 cm), simple, employs a low-cost fabrication technique and offers an alternate sensing mechanism that requires a minimal amount of the MUT. The multiple resonances exhibited by the proposed sensor add to the reliability and accuracy of the sensor.

In this paper, a high front-to-back ratio (FTBR), broad bandwidth planar printing structure, and electromagnetic dipole complementary antenna that generates end-fire radiation pattern is investigated. The antenna consists of a segmented loop, planar electric dipole, and microstrip coupling feed structure, which are printed on the top and bottom surfaces of a dielectric substrate. The segmented loop is equivalent to a magnetic dipole. A high front-to-back ratio is achieved by combining the electric dipole and equivalent magnetic dipole with the same radiation intensity and antiphase. The proposed antenna is fabricated and measured. The measured results show that the proposed antenna achieves an impedance bandwidth of 48.05% (1.66 GHz-2.71 GHz). The largest gain can get to 3.89 dBi, and the maximum front-to-back ratio is 25.4 dB in the frequency band. The measured results are well consistent with simulated ones.

Many static and rotating electric energy converters make use of inductive coils as filters, reactive loads or exciters, where a sudden variation of the magnetizing current can produce severe overvoltage with potential subsequent insulation damage. In some applications the overvoltage is the result of a superposition of travelling voltage waves in a supplying line. Traditional tools for studying such phenomena are based on ordinary differential equations that can heavily handle variable parameters, especially if they change according to the rapidity of the observed overvoltage. In this paper the transient voltage distribution in the excitation winding of a salient pole synchronous generator is simulated by solving the problem entirely in the frequency domain, i.e., without any use of the traditional ordinary differential equations solvers. Thismakesit possible to tune the parameters of a simplified electric model to the frequency response of the studied winding. It is shown that for highly inductive windings a single transmission line model with frequency dependent parameters can reproduce voltage transients very accurately, in a broad interval of frequency, relevant for power electronics and electromagnetic compatibility applications. Furthermore, the paper presents the experimental setup which has been needed for generating the fast varying voltage edges.

The next generation 4T4R Multiple Input Multiple Output (MIMO) antenna solution is gradually accepted by operators in many countries as a mainstream expansion to long term evolution (LTE) networks. Using limited spectrum and high capacity, operators have successfully adopted multi-sector 4T4R MIMO deployment and achieved a 70% increase in capacity without increasing spectrum, thus paving way for state of art next generation wireless networking environment requiring antennae that are robust, small size, lighter, preferably with circular polarization. MIMO antennae provide optimality by arresting multipath fade effect and ensuring data link that is reliable. MIMO realizes efficiency in mobility with increase in capacity of links and several sub-bandwidths using polarization diversity providing better cybersecurity. This work therefore is an investigation on a small size 4T4R MIMO antenna for the use in a sub-6 GHz new radio (NR) band in a fading environment with good inter element as well as radiation isolation compared with earlier research. A rectangular patch with loaded slots is designed to obtain small size. Stubs and parasitic elements are introduced between the elements for better mutual coupling performance. Performance of the antenna is stable, with the test results agreeing. The parametrics follow the coefficient of transmission isolation technique to obtain an optimal envelope correlation coefficient.

An efficient biochemical sensor for the detection of cholesterol concentration using 1-dimensional photonic crystal (1D-PhC) based cavity structure has been proposed in this paper. The structure comprises a 1-dimensional alternating dielectric photonic crystal designed as (A/B)²/D_d/(A/B)² for measuring cholesterol concentration in blood, where `A' and `B' represent high and low refractive index materials, respectively. A cavity containing the cholesterol is inserted in the middle of the structure to assess its concentration. The transfer matrix method is used to analyze the reflection characteristics of the proposed multilayer structure. Sensitivity is analyzed by taking the difference in shifted resonant wavelength by infiltrating varying cholesterol concentrations ranging from 200 to 300 mg/dl. After rigorous optimization, it has been observed that the maximum sensitivity of 2.9 nm/(mg/dl) or 325 nm/RIU can be achieved.

We propose a transmission metasurface (TMS) with ultra-high polarization conversion properties and carrying orbital angular momentum (OAM) vortex waves based on Ku-band's unique periodic unit cell structure in Ku-band. The TMS periodic unit cell structure consists of four cascaded metal layers with parallel-stripe double-arrow and three dielectric layers. We theoretically explain the ultra-high polarization conversion properties of the periodic unit cell by introducing the Jones matrix. Meanwhile, the transmission loss of the periodic unit cell is less than 2.92 dB, and a phase shift of 2π is obtained in 17-19 GHz. We design OAM modes of ±1, ±2, and ±3 for 2π full-phase controlled TMSs by combining the multilayer cascade structure with the Pancharatnam-Berry (P-B) phase principle. The processed TMS produced a vortex wave with an OAM mode of +2 and achieved a polarization conversion rate (PCR) of 83.3% under left-hand circular polarization (LHCP) to right-hand circular polarization (RHCP) in agreement with the simulated and measured data. The results show that vortex waves also have the advantages of high efficiency, broadband, and high mode purity. The generated vortex waves are available for fast beam alignment, which is significant for unmanned aerial vehicles (UAVs) and satellite communications in the Ku band.