The objective of this work is to estimate the Direction of Arrival (DOA) of signals from multiple closely spaced non-Gaussian sources corrupted by additive Gaussian noise. Generally, this is achieved by using higher order statistics (HoS) based MUSIC spectrum. In HoS, the Fourth order Cumulant is utilized because of its property of insensitivity to Gaussian process. But in the case of resolving closely spaced sources, a large number of sensor elements are required; otherwise, the resolution gets deteriorated. The large number of sensor elements leads to high computational burden. We propose a computationally efficient modified Spectrum that combines Fourth order Cumulants based MUSIC spectrum and its second-order differential counterparts. The proposed spectrum for DOA estimation offers good statistical performance and better accuracy the existing methods even in the case of extremely closely spaced signal sources. The improvement in the aspects of resolution and accuracy is substantiated by means of various simulation results such as Monte-Carlo simulations, spectral width, resolution with respect to angular separation, and comparison of RMSE with respect to number of array elements, number of snapshots, and SNR. The computational complexity analysis of the proposed method is also presented.

In order to study the distribution feature of the underwater electric field intensity produced by a ship in restricted seawaters, the horizontal DC electric dipole is used as the equivalent field source. Firstly, four kinds of field models are established. Secondly, the expressions of underwater electric field strength produced by a a horizontal DC electric dipole in the sea areas with upright bank is derived based on the mirror theory of static electric field. Then, based on this, the distribution features of the electric field intensity and the influence of the bank on the electric field are studied by numerical simulation. The simulated results show that the main characteristics of field strength distribution in restricted seawaters are consistent with those without bank, but it makes the absolute value of electric strength increased. The field point is closer to the vertical bank, and it generally presents greater influence on the absolute value of electric strength. But the influences of single vertical and parallel banks on the three-component field strength are different. The effect of bank on field intensity distribution in other restricted seawaters can be regarded as a superimposed effects of a series of vertical or parallel banks. Finally, the rectangle marine environment is simulated in laboratory, and the horizontal components of electric field intensity distribution on a certain depth plane under the simulated field source are measured. These theoretical derivation and analytical conclusions of simulation are further confirmed by comparing with the simulated results.

A dual-mode band-pass filter (BPF) for the fifth generation (5G) N78 band applications is proposed based on a 2-layer low temperature cofired ceramic (LTCC) substrate. The proposed BPF is built with a square resonator and two pairs of open-stubs, which suppressed the 2nd-order and 3rd-order 27 and 21 dB, respectively. The proposed BPF not only achieved a size reduction of 50% compared with a single-mode implementation, but also possessed a non-orthogonal input/output (I/O) feeding style, which presents convenient interconnection and integration with neighboring devices. Moreover, the dual-mode BPF does not need a conventional disturbing element to excite two degenerate modes. Comparison and discussion are carried out as well.

In this paper, a three-dimensional (3-D) tunable band-stop frequency selective surface (FSS) with wide tuning range is presented. The proposed tunable 3-D FSS consists of a periodic array of an annular resonator loaded with two varactor diodes. By controlling the reverse voltage of the varactor diodes, the resonance frequency could be tuned in a wide frequency range. Full-wave simulation shows 100% tuning range from 3.0 GHz to 6.0 GHz with respect to lower resonance frequency. The simulated results exhibit stable band-stop performance under different incident angles (up to 45˚). By cascaded two 3-D tunable FSSs, the bandwidth and selectivity performance could be further enhanced. The proposed 3-D FSS with its stable stop-band performance can be a potential candidate to shield the RF signals which is the major source of problem leading to RF device malfunctions.

In this research work, a planar crossed exponentially tapered slot antenna with a multi-resonance function is introduced. The presented antenna design is ascertained on a low-cost Rogers 5870 dielectric with a circular schematic. The antenna is designed to support several frequency spectrums of the current and future wireless communications. The configuration of the design contains a pair of crossed exponentially tapered slots intersected by a star-shaped slot in the back layer and a bowtie-shaped radiation stub with a discrete feeding point extended among the stub parts. The crossed exponential slots exhibit a wide impedance, and the star slot generates an extra resonance at the upper frequencies. For S₁₁ ≤ -6, the antenna provides a wide operation band of 1.7 to 5.9 GHz supporting several frequency bands of 3G, 4G, and 5G communication. The fundamental characteristics of the proposed slot radiator are studied, and good performances have been achieved.

In the letter, a compact dual-band and dual-polarized antenna integrated into textile for wireless body area network (WBAN) dual-mode applications is proposed. A vertically polarized omnidirectional radiation pattern is generated at 2.45 GHz for on-body mode, while a circularly polarized (CP) broadside radiation pattern resonates at 5.8 GHz for off-body mode. The proposed antenna consists of a compact round rigid substrate and a piece of felt with a full ground. On the upper rigid substrate, a center-fed circular patch with two open annular slots is designed to generate CP radiation. Then four pins are introduced to help the outer ring patch generates an omnidirectional radiation pattern of TM₀₁. The performances of the antenna in free space (FS) and on body (OB) are verified. Besides, the bending characteristics of textile materials are also analyzed. The specific absorption rate (SAR) is simulated, which meets the requirementof the IEEE C95.3 standard. These characteristics make the proposed antenna a good choice for WBAN applications.

The integrated design of 4G LTE and mmWave 5G antennas based on a low cost substrate is proposed for mobile terminals. The 4G LTE antenna is designed along with the millimeter wave 5G antenna element, and this integrated module is mounted orthogonally to cater for smartphone applications. The 4G LTE module consists of two orthogonally placed compact asymmetric coplanar strip (ACS) fed antennas which caters to LTE1900, LTE2300, and LTE2500 bands. ACS-fed antennas operate from 1.8 to 2.7 GHz with a reasonable gain ranging between 1.5 and 2.9 dBi. The mmWave 5G antenna module comprises two compact Vivaldi antennas with wideband operational bandwidth ranging from 23 to 39 GHz. Each mmWave 5G antenna attains 1-dB gain bandwidth of 47.6% indicating high radiation bandwidth across the operating frequency band.Orthogonal pattern diversity is achieved for the usage of smartphone in both portrait and landscape modes. The whole antenna architecture is accommodated to the panel of height 6 mm inside a fabricated three dimensional mobile phone case. Simulated and measured results are presented with technical justification.

A broadband circularly polarized CPW-fed slot patch antenna is presented in this paper. The proposed geometry consists of two unequal L-shaped arms, feeding asymmetrically-shaped slots at two opposite corners to achieve wider circularly polarized bandwidth in stable radiation, without any external polariser. The antenna performance exhibits a wide 3-dB axial ratio bandwidth (3-dB ARBW) of 2.8 GHz, starting from 7.4 GHz until 10.2 GHz, within the 10-dB impedance bandwidth (10-dB IBW) of 3.2 GHz (7-10.2 GHz). Results show a stable radiation in the broadside direction, in which the antenna shows a maximum gain of 4 dBi in bidirectional broadside radiation. The proposed structure occupies a global size of 24 × 22 × 0.25 mm³. The outcomes are achieved making, therefore, the proposed antenna an excellent candidate for performed systems within X band range.

With the increasing number of mobile phone users, new services and mobile applications, the proliferation of radio antennas has raised concerns about human exposure to electromagnetic waves. This is now a challenging topic to many stakeholders such as local authorities, mobile phone operators, citizen, and consumer groups. Thus, the prediction of exposure map at urban scale is a very important requirement to find a relevant indicator of the real exposure. In this paper, we propose a monitoring solution for electromagnetic field (EMF) exposure based on a numerical modeling of the radio wave propagation radiated by mobile telephony base stations. The accuracy of this tool directly depends on the input data precision, such as location of base station antennas or their radiation pattern, which are often poorly known. These data are therefore refined by an optimization algorithm fed by a lot of information, such as the indication of the received signal strength (RSSI) measured directly from users' smartphones, which are used as probes. Results show that this method significantly improves the precision of unknown data concerning mobile base stations and the accuracy of exposure maps at urban scale.

An electrodynamically rigorous mathematical model of a combined vibrator-slot structure consisting of a narrow radiating slot cut in a rectangular waveguide end wall and several thin impedance vibrators placed over the infinite screen is presented. Numerical results concerning internal and external electrodynamic characteristics of the antennas with optimized structural parameters have confirmed the possibility of constructing the Yagi-Uda combined radiating structures in the microwave and extremely high frequency (EHF) bands.

A novel compact patch antenna with Defected Ground structure (DGS) operating for Wireless applications is proposed and investigated. This proposed antenna generates four separate resonances to cover 3.271 GHz (WiMax), 4.92 GHz (WiFi), 6.35 GHz (Space applications) and 11.04 GHz (Fixed Satellite applications) while maintaining overall compact size of 32 × 32 × 1.6 mm³ using an FR-4 substrate commonly available with a permittivity of ε_r = 4.4. The proposed microstrip patch antenna (MSPA) consists of a square radiator in which a Log Periodic slot is etched out along with square defects on ground surface and a microstrip feed line. The log periodic slot with DGS modifies the total current path thereby making the antenna operate at five useful bands. Structure displays the impedance bandwidth of 8.34% (3.10-3.37 GHz), 2.00% (4.88-4.98 GHz), 14.68% (6.27-7.194 GHz), and 5.41% (10.79-11.39 GHz) with gains 3.25 dB, 0.85 dB, 5.65 dB and 4.47 dB respectively. The antenna performance is analyzed using numerous parametric optimization studies, field distributions, and currents. Excellent agreement is obtained between measured and simulated results.

A 16-tupling frequency system for millimeter-wave generation using cascaded arrangement of parallel Mach-Zehnder modulators is presented in this paper. Parallel non-ideal Mach-Zehnder modulators are used to realize a Mach-Zehnder modulator (MZM) with an ideal splitting ratio of 0.5. Hence, parallel MZMs work as a modulator with ultra-high extinction ratio. A 5 GHz radio frequency signal is 16-tupled to 80 GHz with optical sideband suppression ratio of 64 dB and radio frequency spurious sideband suppression ratio of 31 dB respectively. The system has radio frequency spurious sideband suppression ratio ≥ 10 dB for modulation range of 2.79 to 2.86. Further, optical sideband suppression and radio frequency spurious sideband suppression ratios are independent of extinction ratio of MZMs.

This paper presents the design and analysis of an on-chip compatible millimeter wave (mmW) antenna concurrently operating at frequencies 60 GHz and 94 GHz. It is quite challenging to design an antenna at mmW frequency due to propagation of surface waves and use of high index Si substrate for system on-chip (SoC) applications. Hence, in this paper a micromachined mmW antenna design using suspended microstrip technology has been proposed for SoC applications. Dual band operation of the antenna has been achieved by reactive loading at the radiating edge. The designed antenna supports the fractional bandwidth of 3.7% & 5% and gain of 7.68 dBi & 8.22 dBi at 60 GHz and 94 GHz, respectively. The results were also compared using two different EM solvers HFSS and CST which were in close agreement. Parametric effects of different substrate and antenna design parameters have also been analyzed. As a proof of concept, a scaled prototype antenna was fabricated and compared with the proposed mmW antenna.

Aiming at high torque ripple of switched reluctance motor (SRM) caused by hysteresis tolerance control, this study proposes a new deadbeat control based on an SRM rotation coordinate system. The command current is easily calculated on account of the nonlinear deadbeat current controller. For the voltage control, the redefined voltage vectors and space voltage module are discussed to reduce the switching states. Experimental results exhibit that the proposed method can reduce the SRM torque ripple compared with direct torque control and direct instantaneous torque control. In addition, all the results are carried out on a three phase 12/8-poles SRM.

We present an analytical analysis of a metasurface-based ambient electromagnetic energy harvesting system in which the bi-anisotropic particles loaded with a resistor are used. The proposed metasurface composed of an array of bi-anisotropic particles referred to as an electromagnetic energy harvester that can capture the ambient incident electromagnetic wave energy with a radiative to AC conversation efficiency of around 100%. The captured energy by metasurface is delivered to the load. The load acts as the input impedance of a rectification circuit in a rectenna system. The derived optimal polarizable inclusions can be applied to design bi-anisotropic metasurfaces which can be used for electromagnetic energy harvesting. Finally, the optimal dimensions of a typical chiral structure have been calculated to achieve maximum efficiency for circularly polarized propagating waves.

In this work, an elliptical planar monopole Penta band-notched ultra-wideband (UWB) antenna is proposed. Band rejection at 2.4-2.6 GHz IEEE 802.11 b/g/n, 3.3-3.75 Wi-MAX, 3.9-4.2 GHz C-band satellite communication, 5.15-5.85 WLAN, and 7.9-8.4 GHz X-band satellite communication frequencies is achieved by etching slots in the radiating patch, feed line, and ground plane. The effect of the slot length on the notched band is also studied. The proposed antenna has been fabricated and tested. The measured impedance bandwidth of the antenna is 2.15-12.5 GHz, which covers bands of Bluetooth and UWB applications. The peak gain of the proposed antenna is 8 dB and drops drastically at notched bands. The proposed antenna shows good omnidirectional radiation patterns in the passbands.

A low-profile circularly polarized (CP) antenna for a handheld Ultra-High Frequency Radio Frequency Identification (UHF RFID) reader is proposed in this paper. The radiating part on the top substrate is composed of three inverted-F elements rotated 120˚ around the center of the structure. A power splitting circuit, placed on the bottom substrate, based on a series transmission line feed delivers equal amplitude to the three IFA with a sequential 120˚ phase shift. Both layers are fabricated on low-cost FR4 material. This design has a disk form factor with a compact size of 35 mm circle radius and an 8.6 mm height. The measurement shows good results with S₁₁ as lower than -10 dB for the whole band, 3 dB-axial ratio around 110˚ (10 MHz of bandwidth), directivity reaching 4.4 dBic, and the total gain of the antenna is 1.9 dBic. In order to validate the proposed antenna performance, a UHF RFID handheld reader is built based on the ThingMagic M6E-Nano module. Different scenarios are investigated to validate the proposed antenna performance in a real environment.

In this paper, a new monopole compact antenna with tunable frequency fed by a coplanar waveguide (CPW) for WiMAX, WLAN, LTE bands, and X-band satellite communication system is presented. This is achieved by adequate combination of a new radiating patch element along with slots and switches. The simulation and measurement results show that depending on ON/OFF states, the proposed reconfigurable antenna, printed on an FR4 substrate, can operate in four applicable frequency bands, i.e., [2.37-2.75 GHz], [3.15-4.08 GHz], [4.48-5.92 GHz], and [6.69-8.31 GHz]. Very interesting results for the reflection coefficient, current distribution, and radiation pattern of the antenna are presented and discussed. The measured results are in good agreement with the simulated ones.

This work presents the modelling of a highly efficient all-metal slotted waveguide array antenna (SLWA) at sub-THz frequencies for the 5th generation communication applications or beyond. The slotted waveguide array antenna is modified for the accomplishment of high gain, wide bandwidth, and circularly polarized broadside radiation pattern. The proposed double `T'-shaped slot (DTS) which acts as an active element in the whole antenna radiation and other elements after DTS contribute high directivity and gain. The designed slotted waveguide array antenna with DTS is modified for the reconfiguration of linear polarization into circular polarization and achieves the axial ratio (AR) below 3 dB for the bandwidth of 22.323 GHz with a maximum gain of 14.4 dBi. The length and shape of the slot are altered in the SLWA in-order to set up the advanced rectangular stepdown slots (RSDS) and cross stepdown slots (CSDS) for the circularly polarized beam scanning application. The RSDS SLWA, and CSDS SLWA provide wide impedance bandwidths of 56.506 GHz and 61.236 GHz with 3 dB AR range of 12.417 GHz and 9.688 GHz, respectively. The design and simulation of the proposed antenna are done in CST microwave suite and validated using HFSS software.

A low-profile, printed dipole antenna having two feed ports with two parasitic strips for tri-band operation in the 2.4 GHz (2400-2484 MHz), 5.2 GHz (5150-5350 MHz), and 5.8 GHz (5725-5825 MHz) wireless local area network (WLAN) bands is presented. The strip dipole is coupled-fed via a chip capacitor connected to a dual-feed network and generates the 2.4 and 5.2 GHz bands with the aid of the tuning stubs in the feed network. The two parasitic strips are further employed to introduce additional resonance to cover the 5.8 GHz band. It was found that by loading the chip capacitor with proper values between the strip dipole and the dual-feed network, the port decoupling in both the 2.4 and 5.2 GHz bands can be improved, making a dual-feed and yet single antenna system possible. The design with constant strip width is simple in structure and occupies a compact size of 5 mm × 40 mm (about 0.04-λ × 0.32-λ at 2.4 GHz), which is well-suited to current narrow-bezel laptop computers.