In this article, two compact Substrate Integrated Waveguide (SIW) bandpass filters based on Defected Ground Structure (DGS) technology are proposed. Hilbert Cell of second orderis the resonator shape proposed for the DGS of both filters, where the first filter DGS consists of five pairs, and the second one uses only three pairs. The pair used in the first filter consists of two cells located side to side whereas they are placed face to face in the second filter. In order to enhance the performance of the second filter and based on the evanescent-mode technique, three other pairs of first order Hilbert cells are engraved on the top layer. Both band-pass filters are designed to operate in C band with a measured bandwidth of 1.8 GHz for the first filter and 0.86 GHz for the second one. The proposed structures have the same physical dimensions, which is 38.1 mm×16 mm with different measured insertion losses of -2.5 dB and -2.7 dB. Both structures exhibit an upper stopband rejection with attenuation around -20 dB and -29 dB, respectively. The filters operate in a transmission bandwidth of [5.5 GHz-7.3 GHz] and [5.27 GHz-6.13 GHz] with a fractional bandwidth (FBW) of 28.1% and 15.09% for the first filter and the second filter respectively. A good agreement is reported between the measured and simulated results.

This work presents a design and analysis of a high gain Antipodal Vivaldi Antenna (AVA) with quad band notch characteristics for Ultra-Wideband (UWB) applications. The proposed AVA is designed on a 1.2 mm FR4 substrate with dielectric constant 4.3 and loss tangent 0.025. Initially, the AVA parameters are optimized in a full wave simulator to get the required UWB performance. The UWB performance is further improved significantly by cutting a C shaped slot from the AVA flares. The C shaped slot introduces an extra resonance that widens the initial bandwidth. The band-notched filtering characteristics are achieved by - adding a Sun Shaped Slot (SSS) on the top and bottom flares of the AVA, inserting a hexagonal shaped Complimentary Split Ring Resonator (CSRR) on the ground plane of the AVA and finally by inserting vias on either side of the feed line. The first designed notch band is from 2.2-2.7 GHz, covering the Bluetooth region. The second notch band is designed from 3.3-3.6 GHz, corresponding to WiMAX applications, and the third notch band is from 4.6-5.7 GHz corresponding to the WLAN band. Finally, a notch is fashioned from 8.8-9.5 GHz, corresponding to ITU applications. The simulated and measured return loss plots show that the antenna achieves an impedance bandwidth of 1.15-14 GHz with a reflection coefficient less than -10 dB, except at the four eliminating bands. To the best of the authors knowledge, the proposed technique is novel, and it allows good narrowband rejection over the UWB regime.

As unmanned aerial vehicle (UAV) is widely used in many civilian fields the wideband (WB) high power electromagnetic radiation devices development, whether the WB radiation would influence the civilian UAV to fulfil its tasks needs to be analyzed. Therefore, the radiated susceptibility of three models of DJI UAVs is studied in the paper. A decimetric wave oscillator with the power of over 500 MW was introduced as the radiation source. In experiment, adjusting the distance between radiation antenna and UAVs to change the electric field and the testing antenna was employed to measure the electric field on line. The three models of UAVs can be shot down by the electric field of 10 kV/m, 20 kV/m and 30 kV/m, respectively. Besides, as electric field reached up to over 35 kV/m, the rotor motor, electric control system and inertial measurement unit (IMU) in Mavic Air and Mavic Air 2 were easier to burn down. Except that, the energy accumulation effect has been proved in the experiment. In conclusion, the UAVs should fulfill tasks in the WB electromagnetic environment whose electric field is much less than 10 kV/m, and some shielding methods are needed to make UAV survive.

In this paper, we propose a wideband polarization diversity multiple-input multiple-output (MIMO) antenna array for 5G smart mobile devices. The proposed MIMO antenna array consists of 8-ports dual-polarized L-shaped lines that highly excite radiating slots, where the elements are placed at four-corners of a compact mobile unit of size 75×150 mm². The uniqueness of the proposed MIMO antenna structure comes from the deployment of octagon-shaped resonant slots within the metallic ground plane, i.e. the octagonal-slots are etched from the bottom (ground) layer of the main mobile board. Due to the unique slots in the ground plane, wideband impedance has been achieved (3.38-3.8 GHz at -6-dB threshold). The proposed smart phone 8×8 diversity MIMO antenna is designed to support the spectrum of commercial sub-6 GHz 5G communications and cover the frequency range of around 3.5 GHz band with high decoupling between antenna ports. The proposed array is designed, numerically simulated, fabricated and tested. Good agreement between simulated and measured results was achieved. The MIMO antenna has a satisfactory far-field performance along with very low envelope correlation coefficient (ECC) < 0.055, high diversity of more than 9.95, and very low specific absorption rate (< 1 W/Kg for a 10-g human tissue).

In this work, a novel all-textile washable metasurface antenna is designed for WBAN/WLAN and mid-band 5G applications. Metasurface antenna is obtained by implanting SRR (Split Ring Resonator) metamaterials that show left-hand characteristics to the patch plane. The metasurface arrays consisting of 4×1 and 4×2 SRRs are placed to both sides of a circular patch. The performance of the antenna is verified by a full-wave electromagnetic analysis tool. The results show that metamaterial arrays significantly increase gain and efficiency values of the circular patch antenna. Metasurface antenna consisting of 4×2 array of metamaterials increases the efficiency from 74% to 94.5% and the antenna gain from 6.81 dBi to 9.43 dBi. Performance of the antenna is observed on conformal surfaces, as well. An analysis is carried out to calculate the peak specific absorption rate on an arm phantom. Patterns of vertically bended antenna in ø=0° and 90° planes and low SAR values up to 30 dBm input power proved suitability of the metasurface antennas for on-body applications. The antennas are fabricated by using standard textile manufacturing techniques. It was confirmed by the measurement results that the metasurface formed by the linear SRR arrays increases the antenna gain. With its low cost, fabrication with standard off-the-shelf parts, high gain, and efficiency features, the proposed antenna can be used in wireless body area networks and 5G applications.

One of the common ways to design large arrays is by designing a small subarray known as cluster and using it as a repeating element throughout a large array. In this paper, the genetic algorithm is used to optimize the clustered amplitude tapers such that the final array pattern has minimum grating lobes and controlled sidelobe level. The formulation of the synthesis problem includes the minimization of the excess magnitude of the grating lobes or peak sidelobes which are usually higher than a given allowable limit. Moreover, two clustered configurations based on increased/decreased number of elements per cluster around the array center are introduced. Correspondingly, their clustered sizes increase/decrease as they approach the center of the array. Simulation results show that the proposed method has capability to optimize clustered linear and planar arrays without noticeable appearance of undesirable grating lobes. The analysis for an array composed of 20 elements with clusters of different cluster sizes M = 10, 8, 5, 4 and different numbers of elements per cluster N_s = 2, 3, 4, 5 elements found that the complexity reductions were 50%, 60%, 75%, 80%; peak sidelobe levels were -29 dB, -23.6 dB, -21.3 dB, -19.15 dB; and the directivities were 25.53 dB, 25.64 dB, 26.33 dB, 26.32 dB, respectively.

It is of great practical value to study the blended rolled edge of reflector used in Compact Antenna Test Range (CATR). Taking a rectangular aperture reflector as the benchmark, a reflector with ideal blended rolled edge is obtained by means of parameter iterative optimization after accurately establishing the position relationship between the local and global coordinates where the blended rolled edge is located, precisely deriving the geometric equation of the main reflector zone and blended rolled edge zone in the local coordinate, and optimizing continuity condition of curvature radius. On the basis, a blended rolled edge reflector with minimum operating frequency of 0.8 GHz and quiet zone size of 2 m is designed. The simulation results show that the performance of the reflector with blended rolled edge obtained by the proposed method is better than that obtained by the traditional construction method, and the designed reflector has excellent performance. The work in this paper provides a theoretical support for the optimal design and engineering application of the blended rolled edge reflector.

This paper covers the use of oscilloscopes in near-field, pre-compliance radiating tests. Using commercial low-cost planar magnetic probes, a procedure is presented to use the time-domain waveforms to address emitted radiation patterns. In spite of its lower sensitivity in relation to spectrum analyzers, a comparison between both instruments is presented, with the inferior response of the oscilloscope compensated by means of off-the-shelf broadband amplifiers. Complete system calibration is described and performed, relating the voltage measurements in a transmission-line structure to field amplitudes provided by a full-wave simulation. Two different typical devices are tested using the procedure here developed: a direct current motor, driven by a square wave, and a microprocessor board. Results show the potential use of the almost omnipresent instrument in sophisticated field evaluations, enabling its use in situations where spectrum analyzers are not available.

In the medical world, the continuous monitoring of patients having a long-term illness is mandatory. The usual monitoring systems placed around the patients are bulkier and costly. Moreover, the movement of those patients is limited as they are connected to the monitoring devices with probes. To enable the locomotion of the patients a miniaturizedimplantable antenna sensor with the dimension 2.5 x 7 x 0.25 mm³ is proposed to monitor arterial pressure. The proposed antenna sensor is fabricated and verified for its performance metrics. Radiation analysis for the implants is carried out through a metric called Specific Absorption Rate (SAR). Deviation of pressure in the patient is measured through the rate of change of resonant frequency through an external reader coil. Communication established between the Transmitter (patient with implant) and the Receiver for better monitoring is verified through field strength calculated at various locations inside the hospital rooms in order to allocate rooms for the post-operative/long term ill patients efficiently.

In this paper, a compact UWB antenna with a reconfigurable and sharp dual-band notches filter to cancel the interference with some critical applications (5G WLAN, and X-band satellite downlink) is proposed for underlay cognitive radio (CR) applications. The dual notched bands are produced by coupling a pair of π-shaped resonators on both sides of the feed line and by etching a U-slot inside the feed line of the antenna. The proposed UWB filtenna in this configuration has a surface area of 22×31 mm² and produces simulated (measured) reconfigurable notched frequencies at 5.466 GHz (5.7 GHz) and 7.578 GHz (7.44 GHz) with an impedance bandwidth of 3.024-10.87 GHz (2.825-10.74 GHz). Three PIN diodes are used to switch the presence of the dual-band notch. Two PIN diodes turn ON-OFF simultaneously (D_1A & D_1B) are inserted within a pair of π-shaped resonators to control the 5G WLAN band notch, and a single diode (D₂) is embedded within a quarter wavelength resonator which is located inside the feed line of the antenna for controlling the X-band band notch. The simulation and measured results reveal that the proposed filtenna effectively covers UWB with controlled cancellation for the interference with the intended bands. The realized gain is 4.5 dBi through the passband except in the notched frequencies, where it is decreased to less than -11 dBi in both notch frequencies. In other words, the proposed filtenna has a very high VSWR of greater than 20 at the notched frequencies.

For the principle that intermittent sampling and repeater jamming (ISRJ) is obtained by discontinuous sampling of radar signal in time domain, a novel random redundancy (RR) waveform based on multiple input multiple output (MIMO) radar and multi-carrier phase code (MCPC) radar signal is proposed, namely RR-MCPC signal. From the point of waveform design, chaotic sequences are used to encode each chip in time domain for the signal with a multi-carrier phase code multiphase coding structure. Moreover, some chips are randomly arranged with equal amount of redundant coding in time-frequency domain. In MIMO radar, the subcarriers of radar signal are divided into multiple channels for transmission, and then the received signal is processed in each channel. Ensure that the intermittent sampling, whether in time domain or frequency domain, will sample redundant information in a channel. So it cannot match the matched filter. Therefore, the RR processing makes the signal have the characteristics of anti-ISRJ, which can availably restrain the interference of ISRJ false target. The results show that the signal-jamming ratio (SJR) improvement factor of RR-MCPC signal after pulse compression is optimized by 2.47-2.69 dB compared with the multi-carrier phase code signal under the typical parameters expressed in this paper.

The purpose of this study is to embed an antenna on very thin textile materials. A rectangular Fractal Antenna is chosen for this application. This antenna radiates for three different frequencies viz. 2.4 GHz, 4.2 GHz and 5.9 GHz. The substrate materials used for three antennas are Poly Viscous, Poly Cotton and Linen which are easily available. Instead of using traditional method applying copper plate or copper layer on substrate material, a simple process of pasting carbon conductive ink on substrate materials is used. On each textile antenna above mentioned frequencies are radiated. Performance parameters of all three antennas are simulated and matched with practical results. The optimum antenna having the best result is used for Wi-Fi Applications.

A novel reconfigurable sub-6 GHz microstrip patch antenna operating at three resonant frequencies 3.6, 3.9, and 4.9 GHz is designed for 5G applications. The proposed antenna is constructed from metamaterial (MTM) array with a matching circuit printed around a printed strip line. The antenna is excited with a coplanar waveguide to achieve an excellent matching over a wide frequency band. The proposed antenna shows excellent performance in terms of S₁₁, gain, and radiation pattern that are controlled well with two photo resistance. The proposed antenna shows different operating frequencies and radiation patterns after changing the of photo resistance status. The main antenna novelty is achieved by splitting the main lobe that tracks more than one user at same resonant frequency. Nevertheless, the main radiation lobe can be steered to the desired location by controlling the surface current motion using two varactor diodes on a matching circuit.

This paper proposes the design and implementation of a circular triangle fractal antenna for portable ultra-wideband (UWB) communication applications with band rejection at WLAN band. The presented antenna is made with iterative generation of a circular triangle shaped elements arranged in circular fashion with self-similarity and periodicity property with coplanar waveguide feed. The overall dimensions of the antenna are 28× 27 x 1.6 mm³. The fractal resonating plane and ground plane dimensions of the proposed antenna are optimized to obtain a resonance bandwidth of 2.39-12.28 GHz which corresponds to fractional bandwidth of 134.8% with notch band from 5.45 to 6.27 GHz to mitigate the problem of interference from WLAN. The peak gain detected is 11.16 dBi. The proposed prototype was fabricated on a 1.6 mm thick FR4 material with the relative permittivity of 4.4, and the sample was tested. The experimental results are in close agreement with the simulated ones. The time domain analysis indicates that the proposed antenna is not dispersive. The antenna radiates in a virtually omnidirectional pattern. Due to these merits, this proposed antenna can be used in UWB applications.

The advent of space exploration and space warfare along with the deployment of advanced missiles, unmanned aircraft systems, and modern nuclear reactors has reignited the field of high temperature antennas. In this context, this article surveys the field of antennas that operate under harsh environments that are often characterized by high temperature. In this context, this article surveys the field of high temperature antennas. The choice of the substrate and the conductor for antenna implementation are discussed with emphasis on their thermal and electrical properties. Further, the different fabrication techniques to realize the antenna are discussed. The performance comparison of the different types of high temperature antennas are presented. Finally, the future prospects and inherent challenges in advancing research on antennas for extreme environments are detailed. The article concludes with insights into the new developments in the field of flexible antennas operable in hostile conditions.

TDFA-band (2-μm waveband) has been considered as a promising optical window for the next generation of optical communication and computing. Absorption modulation, one of the fundamental reconfigurable manipulations, is essential for large-scale photonic integrated circuits. However, few efforts have been involved in exploring absorption modulation at TDFA-band. In this work, variable optical attenuators (VOAs) for TDFA-band wavelengths were designed and fabricated based on a silicon-on-insulator (SOI) platform. By embedding a short PIN junction length of 200 μm into the waveguide, the fabricated VOA exhibits a high modulation depth of 40.49 dB at 2.2 V and has a fast response time (10 ns) induced by the plasma dispersion effect. Combining the Fabry-Perot cavity effect and plasma dispersion effect of silicon, the attenuator could achieve a maximum attenuation of more than 50 dB. These results promote the 2-μm waveband silicon photonic integration and are expected to the future use of photonic attenuators in crosstalk suppression, optical modulation, and optical channel equalization.

Wearable antenna is one component needed for mid-range communication. It can be integrated into clothing, bags, or any other item worn. This paper presents the structure and performance of a wearable antenna used in place of the ESP8266 Wi-Fi module antenna in dresses. With a higher gain than 2 dBi, this replacement will provide greater signal coverage than the existing Wi-Fi antenna module. The proposed geometry utilizes rectangular patches with the inset feed method in the feedline segment, constructed using copper foil tape, 2.85 mm thick polyester as a substrate with a permittivity (ε_r) of 1.44, and Defected Ground Structure (DGS) technique. The operating frequency of the proposed antenna is at 2.4 GHz in ISM (Industrial, Scientific, and Medical) band. The whole process was used to optimize the structure, fabricated, and measured. As determined by simulation, the proposed antenna's return loss is -13.89 dB, whereas the measured value is -13.253 dB. The measurements scenario for the substitute and existing antenna are divided into two categories: line-of-sight (LoS) and non-line-of-sight (NLOS). Each of them experiences vertical and horizontal position of antenna. In LOS conditions, the vertical position has an average coverage of 9.84 meters more than the antenna module and the horizontal position is 13.84 meters. In NLOS conditions, the horizontal position has an average coverage of 9.22 meters more than the EP8266 antenna module, which in the vertical condition is about 17.06 meters. The obtained data successfully demonstrated that the proposed antenna could significantly increase the coverage of the ESP8266 module.

We propose the squeezing of hyperbolic polaritonic rays in cylindrical lamellar structures with hyperbolic dispersion. This efficient design is presented through conformal mapping transformation by combining with circular effective-medium theory (CEMT) that is adopted to predict the optical response of concentric cylindrical binary metal-dielectric layers. The volume-confined hyperbolic polaritons supported in these cylindrical lamellar structures could be strongly squeezed when they propagate toward the origin since their wavelength shortens, and velocity decreases. To demonstrate the importance of using CEMT for engineering highly-squeezed hyperbolic polaritons, both CEMT and planar effective-medium theory (PEMT) are utilized to design the cylindrical lamellar structures. It is shown that the PEMT-based design is unable to achieve hyperbolic polaritons squeezing even with a sufficiently large number of metal-dielectric binary layers. Remarkably, this study opens new opportunities for hyperbolic polaritons squeezing, and the findings are promising for propelling nanophotonics technologies and research endeavours.

To enhance transmission performance, a novel three-coil wireless power transfer system is proposed in this work. Unlike the traditional system in which three coils are resonant, the coils in the proposed system are hybrid resonant. According to theoretical calculation, it is found that output power is dependent on resonant frequency of the transmitting coil and the relay coil once the receiving coil is set to resonate at the operating frequency. Simulation work is conducted. Under various distance between transmitting coil and relay coil, resonant frequency of the two coils at which the output power is maximized is obtained. Compared with the traditional resonant system, the simulation result shows that output power of the proposed hybrid resonant system is higher especially at smaller distance. For further validation, experiments have been carried out which verify that better performance can be realized with the proposed hybrid resonant system.

An electronically reconfigurable reflectarray antenna of 12 × 12 units is presented in this paper. The element consists of a slotted square patch and a gapped metal square ring. PIN diodes are loaded on slotted square patches, which can be electronically controlled to produce two states with 180˚ phase difference. A reflectarray prototype is fabricated and experimentally studied. Experimental results agree well with the full-wave simulations by Ansys HFSS, and scanning beams within ±45˚ range are obtained with a maximum aperture efficiency of 14.9% at 5.8 GHz. 1-dB bandwidth is 9.9%, and 3-dB bandwidth is 19.1%.