Radio-frequency electromagnetic waves can be harnessed to produce an alternative source of energy to replace batteries in many low-power device applications. An efficient radio frequency (RF) energy harvesting circuit was designed and constructed using a dynamic Pi-matching network in order to convert frequency-modulated electromagnetic waves in the range of 88-108 MHz to direct current through a 3-step process. The circuit consists of a 50 Ω copper plate dipole antenna, a Pi impedance matching network, and a five-stage voltage doubler circuit. These three modules are connected through SubMiniature version A (SMA) connectors for convenient assembly. The dynamic Pi matching technique for RF energy harvesting is theoretically explained and simulated in the Advance Design System software environment. The experimental values obtained in this proposed work are in good agreement with the simulations. The harvesting system is capable of producing up to 14.3 V direct current voltage across a 100 kΩ load in field tests carried out at a displacement of 760 m from a transmission tower. At 6.7 km from the tower, a DC value of 61.5 mV was still obtainable at the ground level. The direct-current power that was generated through the energy harvesting was applied for the demonstration of three tasks with satisfactory results: illuminating a light-emitting diode, energy storage in a Panasonic VL2020 rechargeable battery, and activation of a TMP20AIDCKT temperature sensor in an urban area which enabled low power device activation and energy storage.

To restore power feeding as soon as possible and reduce repair costs and labor, a precise and robust fault location method for transmission lines is proposed. This method is based on the current and voltage synchronously collected by the phasor measurement units (PMUs) at two terminals of the line and does not require line parameters to calculate the fault distance. The line parameter is not approximately constant, but is affected by power load, temperature, and humidity, which affects the accuracy of most fault location algorithms that rely on line parameters. Therefore, the method proposed in this paper is robust and accurate. The method is based on the sequence fault component network and synchronous measurement technology, which is not affected by the system's pre-fault state, fault type, fault inception angle, and fault phase. Then, the method is verified in PSCAD/EMTDC by choosing different path resistances, fault types, fault inception angles, load currents, and line transpositions. A large number of simulation results show that the proposed method has high accuracy and robustness.

We propose a compact microstrip patch antenna that uses a negative permittivity substrate to achieve an end-fire radiation pattern. The antenna is designed to operate at X-band frequencies with a patch footprint of 0.9λ × 0.05λ and a thickness of λ/20. We show that loading a narrow patch with a negative permittivity substrate introduces an effective shunt inductance that resonates with the strong fringing capacitance of the patch. At resonance, the electric field is vertically polarized and approximately uniform across the patch, producing transverse nulls that improve the directivity of the antenna. The negative permittivity substrate is implemented using a thin-wire effective medium with four vias spread across the patch. The antenna is matched to 50 Ω using a quarter-wavelength transformer. The fabricated antenna operates at 10.8 GHz with a peak return loss of 30 dB and a bi-directional directivity of 10.7 dBi. The antenna has a 10-dB impedance bandwidth of 3.8% and radiates with a simulated efficiency of 93%.

Although the design of multiband band-pass filters (MBPFs) has been thoroughly studied in the literature, the synthesis of high-order and multiple pass-band filters with controllable transmission zeros (TZs) and high band-to-band isolation is hardly feasible. In this paper, we present a novel design strategy to cope with this issue. Adopting a star-like topology, the proposed design method is based on the parallel association of N-1 band-stop stepped-impedance stubs to form an N pass-bands resonator. We show that such a simple design principle allows the accurate control of TZs positions. The principle and theory of these associated band-stop resonators (ABSRs) based filter are exposed, and their efficiency is shown through the synthesis, design, simulation, and measurement of quad-band and quint-band band-pass filters. Very good in-band filter performance and very high band-to-band isolation are achieved for both filters without the need for complex optimization process. These results make the ABSRs an attractive solution to achieve multiple band responses with advanced specifications.

A portable 4D snapshot hyperspectral imager (P4DS imager) with compact size, fast imaging time, low cost, and simple design is proposed and demonstrated. The key components of the system are a projector, a liquid crystal tunable filter (LCTF), and a camera. It has two operating modes dependent on the set state of the LCTF: a 3D light measurement mode that produces a 3D point cloud reconstruction of the object, and a hyperspectral imaging mode yielding spectral data. The camera imaging plane is the same for both operating modes allowing the collected spatial and spectral data to be directly fused into a 4D data set without post-processing. The P4DS imager has excellent performance with a spectral resolution of 10 nm, a spatial depth accuracy of 55.7 um, and total 4D imaging time of 0.8 s. 4D imaging experiments of three different samples, colored doll statue, green broccoli, and a human face, are presented to demonstrate the efficiency and applicability of the system. Due to being cost-effective, portable, and good imaging performance, the proposed system is suitable for commercialization and mass production.

Birds and bats are at risk when they are flying near wind turbines (WT). Hence, a protection of bats and birds is postulated to reduce their mortality e.g. due to collisions with the rotor-blades. The use of radar technology for monitoring wind energy installations is becoming increasingly attractive for WT operators, as it offers many advantages over other sensor systems. Timely localization and classification of the approaching animal species is very crucial about the reaction measures for collision avoidance. In this work, a localization, classification and flight path prediction technique has been developed and tested based on simulated radar signals. This allowed us to classify three different birds and one bat species with an accuracy of 90.18%. For accurate localization and target tracking, five frequency modulated continuous wave (FMCW) radars operating in Ka-Band were placed on the tower of the WT for 360˚ monitoring of the WT.

Small footprint of the multi-input-multi-output (MIMO) antenna is extremely desirable for space-constrained ultra-wideband (UWB) communication systems. Compact MIMO antennas with improved isolation and wide operating bandwidth are the significant subject of the work. Therefore, this paper presents a miniaturized four-port polarization diversity UWB-MIMO antenna operating in the frequency range of 3.1-12 GHz with band-notched characteristics. Four octagon-shaped radiating elements with a common ground are placed orthogonal to each other for good isolation. Band rejection features between 4.5 and 5.5 GHz were achieved by including an open-ended slot at the upper edge of the octagon-shaped antenna. The MIMO antenna was etched on a low-cost 32.3 x 32.3 x 0.8 mm³ FR-4 dielectric substrate. The antenna radiates in a quasi-omnidirectional pattern on the H-plane throughout the operational bandwidth, with higher than 15 dB isolation, low envelope correlation, and high antenna gain. As a result, this antenna is well suited for diverse applications and portable devices.

Compact low-profile four and eight elements Multi-Input Multi-Output (MIMO) antenna arrays are presented for 5G smartphone devices. The proposed antenna systems can operate at two dual-wideband with triple resonance frequencies that cover the extended Personal Communication Purposes (PCS) n25 band and other related applications, the mobile china's band, and the LTE Band-46. The proposed antenna element is designed based on modified Minkowski and Peanocurves fractal geometries. Desirable antenna miniaturization with multi-band capability is obtained by utilizing the space-filling and self-similarity properties of the proposed hybrid fractal geometries where the overall antenna size is (11.47 mm × 7.19 mm). All antennas are printed on the surface layer of the main mobile board. Based on the self-isolated property, good isolation is attained without employing additional decoupling structures and/or isolation techniques, increasing system complexity and reducing antenna efficiency. For evaluating the performance of the proposed antenna systems, the scattering parameters, antenna efficiencies, antenna gains, antenna radiation characteristics, envelope correlation coefficients (ECCs) and mean effective gains (MEGs) are investigated. The performances are evaluated to confirm the suitability of the proposed MIMO antenna systems for 5G mobile terminals. The proposed eight elements MIMO system has been fabricated and tested. The measured and simulated results are in good agreement.

In this paper, a wide-band cavity antenna with low scanning loss for 20% antenna bandwidth as well as having a wide 20% 1-dB gain bandwidth over the antenna beam scanning angle is proposed. The antenna operates in the 5 GHz band of IEEE 802.11 ac wireless local area network (WLAN) applications. A beam scanning of 20˚ is demonstrated by varying the height of a slider within the antenna cavity. The broadside peak gain of 9.6 dBi is maintained for 20% of the antenna bandwidth with a gain reduction of only 0.3 dB throughout its operating frequency range. Besides, the scanning loss suffered by the antenna when scanning from the broadside to the maximum scanned angle is only 0.8 dB. The proposed scan performance is verified for a single element antenna and a two-element antenna array.

A linear-to-linear cross-polarization converter (CPC) based on metasurface (MS) is proposed. The converter is polarization insensitive and has two wide bands. The MS is composed of periodical unit cells printed on a substrate. The top and bottom MS unit cells are formed with four groups of right-angle triangle pairs whose vertices are connected. Thus, there are eight pairs of triangles on the top and bottom surfaces of the substrate, and these pairs of triangles are arranged alternately in overlapping and orthogonal ways. Simulated and measured results indicate that the polarization conversion ratio (PCR) of the CPC is higher than 95% in the bands of 9.4 to 13.1 GHz (32.9%) and 13.4 to 17.2 GHz (24.8%). Additionally, the PCR remains the same when the electromagnetic (EM) wave is incident at arbitrary azimuth. Furthermore, the polarization rotation angle and elliptic angle are calculated to verify the conversion effect. Finally, the conversion mechanism of the proposed converter is explored by analyzing the surface current distribution and magnetic field. The proposed converter can be applied to the field of satellite communication in Ku-band.

As a potential alternative to conventional lenses, metalenses have the advantage of ultrathin volume and light weight. Such miniaturization is expected to apply to compact, nanoscale optical devices such as micro-cameras and high-resolution display. However, chromatic aberration is an important problem in the application of metalenses, which will damage the imaging resolution and color reality for multi-wavelength incident light. Here, we briefly discuss recent development of design methods for achromatic metalenses, containing one or more pieces, and experimental evaluation of their performances.

This paper deals with a new definition of the Radar Cross Section (RCS) suitable for surface wave propagation in the HF band. Indeed, it can be shown that the classical definition of the RCS is dependent on distance for this kind of propagation. Also, in simulation, with the classical definition, the power estimated on the receivers using the radar equation is inaccurate. This is an issue for the performance assessment of High Frequency Surface Wave Radars. Thanks to the analysis of different wave propagation models, the differences between the space wave propagation and surface wave propagation have been highlighted. The required modifications of the RCS can then be performed. The proposed new definition is explained and justified in the paper and has been successfully applied to the computation of the RCS of naval targets. In addition, the implementation of this normalization term into the radar equation, and conversely the gain, is discussed. It can be observed that the received power, determined with the definitions adjusted to the surface wave propagation, is accurate. The different obtained results are illustrated and commented.

In this paper, a new frequency tunable filtering-antenna (so-called filtenna) is inspired by a Defected Ground Structure (DGS) band-pass filter for the fifth generation picocell base stations. It is intended for use in Cognitive Radio (CR) communications within the European Union Sub-6 GHz spectrum, which ranges between 3.4 and 3.8 GHz. Firstly, a Wideband (WB) monopole antenna is proposed where the operational frequencies cover 3.15-4.19 GHz, taking the 10-dB return loss level as a threshold. A band-pass filter of a Semi-Square Semi-Circle shape is integrated into the WB antenna ground to obtain the communicating filtenna. The narrowband frequency tunability is achieved by changing two varactor diode capacitances located on the filter slots. The antenna is prototyped occupying a total space of 60 x 80 x 0.77 mm³, then tested to verify the simulated results. Three operating frequencies 3.4, 3.6 and 3.8 GHz of the filtenna are studied in terms of return loss, realized gain and radiation patterns which verify that the frequency shift has almost no effect on the antenna performance. The filtenna has a maximum gain of 4.5 dBi in measurements and 3.47 dBi in simulations. The obtained results have proved their efficiency for CR communications.

Investigations on radiation characteristics of multilayer antenna having embedment of left-handed material are presented. The proposed engineered comb-shaped structure exhibits both negative permittivity and permeability. The inset-fed patch antenna matched at 50 Ω incorporates a homogeneous array of multilayer comb-shaped resonators. The array demonstrates a major impact on antenna parameters such as resonance, gain, radiation pattern, voltage standing wave ratio, and bandwidth. The novelty in the presented design is that by merely modifying the physical parameters of the negative refractive index resonator, the antenna radiation property can be altered. An artificially realized left-handed stacked material possesses strong inductive and capacitive mutual-coupling. The variations in stacked conductive inclusion illustrate the considerable change in antenna resonance. The antenna resonates at 1.57 GHz, 2.48 GHz, and 3.4 GHz with a bandwidth of around 20.64%, 7.35%, and 4.40% respectively. The proposed antenna electrical size is 0.48λ x 0.56λ at a lower frequency. The antenna exhibits the gain of 3.8 dBi, 6.15 dBi, 4.54 dBi at 1.57 GHz, 2.48 GHz, and 3.4 GHz respectively. The proposed planar stacked negative refractive index-inspired patch antenna model can be utilized for L1 and S-band satellite and maritime operations.

A new planar compact antenna composed of two crossed Cornu spirals is presented. Each Cornu spiral is fed from the center of the linearly part of the curvature between the two spirals, which builds the clothoid. Sequential rotation is applied using a sequential phase network to obtain circular polarization and increase the effective bandwidth. Signal integrity issues have been addressed and designed to ensure high quality of signal propagation. As a result, the antenna shows good radiation characteristics in the bandwidth of interest. Compared to antennas of the same size in the literature, it is broadband and of high gain. Although the proposed antenna has been designed for K- and Ka-band operations, it can also be developed for lower and upper frequencies because of the linearity of the Maxwell equations.

This paper proposes a new method to produce and reconfigure transmission zero(s) (TZ(s)). The TZs are constructed by using lumped elements in series with dielectric resonators, which is different from conventional methods such as introducing a cross coupling between nonadjacent resonators and mixed coupling between adjacent resonators. The proposed filter consists of two dielectric resonators, a capacitor, an inductor, two PIN diodes, etc. Two PIN diodes are used as switches to realize reconfigurable TZ(s). The mechanism is analyzed theoretically. An equivalent schematic diagram is simulated by using ADS software. The simulated results show that the structure can realize four response states, i.e., no TZ in the stopband, one TZ in the lower stopband, one TZ in the upper stopband, and two TZs in both sides of the stopband of the filter, respectively. The dielectric resonators (DRs) were made of dielectric ceramics with high dielectric constant of about 92. The filter was fabricated on a dielectric substrate and measured by using a vector network analyzer and double regulated DC power supply.

In this paper, the design of an Ultra Wide Band (UWB) hemispherical antenna with Log-Periodic Elements (LPEs) capable of operating at multiple resonating frequencies lying in L, S, C, X, and Ku frequency bands is presented. The design consists of a complex structure of silver hemisphere with LPE mounted on an FR-4 substrate fed by a 50 Ω microstrip line. The dependency of the inclination of log-periodic elements mounted on the hemisphere is analyzed with parametric study. The proposed miniaturized antenna uses LPEs to obtain an impedance bandwidth of above 100% and a multi-directional radiation pattern. The measured results show that a wide operating band of 12.63 GHz (1.68 GHz-14.31 GHz) (8.52:1) has been achieved with a multi-directional radiation pattern with a peak realized gain of 8.12 dBi.

A novel layout method of receiving antenna array, which is a sparse random circular aperture array (SRCAA), to raise the power transmission efficiency (PTE) for microwave power transmission (MPT) is proposed in this paper. Different from the conventional antenna array layout, the array element positions of the SRCAA are randomly and uniformly distributed in the circular region. At present, the receiving array mostly adopts the form of uniform full array in the MPT system, and most researches focus on the antenna unit itself to raise the PTE rather than the array layout. In this paper, the initial array is obtained by randomly scattering points in the fixed area, and then the array element position is optimized by the algorithm to maximize the PTE between the transmitter (Tx) and receiver (Rx) of the MPT system. At the same time, the random array element position also plays a significant role in the uniformity of the received power of the receiving array. Therefore, this paper proposes a new index to measure the performance of the receiving array. In order to verify the effective performance of the SRCAA, we carried out a series of numerical simulations. Numerical simulation results show that the SRCAA, as a high-performance and low-cost receiving array, is more suitable for the receiving array of the MPT system than the traditional uniform array.

The present scenario that demands a high data rate by the consumers in wireless communication has imposed a challenge in the present market. Therefore, millimetre wave technology is attracting the interest of researchers and industries. This paper proposes a rectangular planar microstrip antenna with slots in radiating elements as well as in the ground plane. The proposed structure has been designed, simulated and fabricated at a centre frequency of 28 GHz using 5880 RT duroid as a substrate, which has a relative permittivity of 2.2, loss-tangent of 9x10^-4, and thickness of 1.6 mm. By performing the simulation using HFSS Ansys Software and also fabrication and testing, the proposed design attains a maximum gain of 8.735 dBi and a frequency band-width of around 2.815 GHz. The impedance bandwidth response ranges from 26.75-29.565 (10.1%) below the -10 dB line of the S₁₁ plot. The proposed antenna is compact with dimensions of 2.19 x 3.95 mm and has wide bandwidth along with high gain, hence is a good candidate for mm-wave applications besides several innovative antenna-based gadgets. Measured S₁₁ and VSWR results are in consistent with the simulated ones.

In the paper, a compact broadband 3×3 Nolen matrix with flatten output ports phase differences is presented. By using two types of three-branch quadrature couplers, wideband impedance matching and flatten output ports amplitudes are obtained. Besides, imbalanced output ports phase differences are compensated by inserting two differential phase shifters between the couplers. Design equations for the proposed structure are derived, and influences of the two differential phase shifters on the phase differences of the Nolen matrix are investigated. To verify the effectiveness of the structure, a prototype operating at 5.8 GHz is fabricated and measured. Measurement results agree well with the simulated ones. Fractional bandwidths (FBWs) of 31.21% and 45.17% are obtained for 15-dB return loss and 15-dB isolation. Moreover, under the criterions of amplitude imbalance < 1 dB and phase difference < 5°, the measured FBWs are more than 23.20% and 23.96%, respectively.