A cosecant-squared radiation pattern synthesis for a planar antenna array by using the genetic algorithm (GA) is presented. GA makes array synthesis flexible to achieve two desired features, namely, low peak side lobe level (PSLL) and small deviation (ripples) in the shaped beam region. In order to obtain a desired csc² pattern with the PSLL constrained, GA optimizes both the excitation amplitude and phase weights of the array elements. Dynamic range ratio (DRR) of the excitation amplitudes is improved by eliminating the weakly excited array elements from the optimized array without distorting the obtained pattern. To illustrate the effectiveness and advantages of GA, the beam pattern with specified characteristics is obtained for the same array by using particle swarm optimization (PSO). Results show that the performances of GA and PSO are comparable when dealing with small-to-moderate planar antenna arrays. However, GA significantly outperforms PSO on large arrays. Moreover, numerical results reveal that GA is superior to PSO in terms of cost function evaluation and statistical tests.

This paper proposes a miniaturized monopole ultra-wideband antenna with single-frequency rejection. The recommended antenna size is reduced from 58 × 54 mm² to 32 × 54 mm² by the half-cut method. The bandgap design is achieved by placing a dual mushroom type electromagnetic bandgap (EBG) structure on the side of a coplanar waveguide feeding line. The equivalent circuit and surface current distribution were used to analyze and explain the effects of mushroom-like EBG cells and the principle of the half-cut method. Both the prototype antenna and the proposed antenna have been fabricated and tested. From the measurement results, the proposed antenna exhibits good band-stop characteristics and can reject the wireless LAN interference band (5.2 and 5.8 GHz bands). Furthermore, the proposed antenna has considerable gain over the entire operating frequency band except for the notch band.

Three miniaturization techniques were combined in this work to achieve compact size while maintaining optimal performances of a dual-band star shape slotted Microstrip Patch Antenna (MPA) operating at 2.4 and 5 GHz resonant frequencies. High permittivity substrate and slot techniques were used for miniaturization and impedance matching improvement, while DGS technique was necessary for bandwidth enhancement and further miniaturization of the reference MPA. The miniaturized antenna shows a planar structure and occupies very small area of 15.55 x 19.80 mm² achieving patch size area reduction of 71.24% and overall size reduction of 75.42%. Respectable positive gains were maintained with radiation efficiency exceeding 83% and 68% at 2.4 GHz and 5 GHz, respectively. The reference and miniaturized MPAs were fabricated, then their performances were measured and compared to the simulated ones. The measured impedance bandwidths of the miniaturized MPA were around 38% and 13% at the two resonant frequencies respectively, which confirm the originality and suitability of the miniaturized MPA for Wireless Local Area Network WLAN and ISM applications.

Due to the upsurge in internet connected devices in everyday life, a compact embedded wireless device becomes essential to cater multiple frequency-based applications at common platform. Reconfigurability is the best solution to enhance the device utility at many technical interfaces. Wireless compatibility among different devices via internet elicits the importance of antenna unit. In this paper, a compact size 25×25 mm², five-band frequency reconfigurable antenna is presented. The antenna exhibits the choice-based optimized frequency responses of slot structures, corner truncation and parasitic loading. These individual responses comprise the high frequency switching characteristics in synchronized module of three PIN diodes. The antenna is designed to operate among five different frequencies i.e. 3.85 GHz, 4.14 GHz, 4.43 GHz, 4.91 GHz, and 6.01 GHz. The work emphasizes the compact design and wide switching ability of the antenna, which validates its unique feasibility for high speed multiple applications of Internet of Things (IoT) through a common embedded platform under WLAN, Wi-Max, and C-band applications as per the FCC standards.

In this article, a two-dimensional (2D) unconditionally stable finite-difference time-domain (FDTD) approach is proposed for graphene electromagnetic (EM) device simulation. The weighted Laguerre polynomials (WLPs) are utilized to resolve stability concerns, and graphene is modelled as a thin conductive layer incorporating the surface boundary condition (SBC) in WLP-FDTD scheme. The transmittance of EM signal propagating through two graphene layers is calculated for 0-10 THz to verify the effectiveness of the proposed method. The simulation results agree excellently with the results calculated from the analytical and other numerical models. The proposed SBC-WLP-FDTD method provides an alternative numerical approach to simulate graphene-like materials with improved computing efficiency.

A novel aspect independent resonance based radar target discrimination method has been developed in a previous work, and is found to be effective in discriminating canonical shape closely resembling objects with minor structural variations. The method utilizes the Radar Cross Section (RCS) of the unknown target to be identified and the distinction polynomial stored in the database (built from the dominant resonances of the known target). In this paper, the method is implemented successfully to discriminate two real size F5 aircraft with minor structural variations between them. This study involving real size targets poses some challenges that are overcome in this paper. The foremost challenge is the accurate computation of resonance range RCS of electrically large sized target considered (> 10λ), which is computationally demanding. The second challenge is in selecting the dominant resonances (features) of the complex target, useful for discrimination, from a large set of resonances representing the target. The accuracy of the discrimination result is dictated by the accuracy with which the features of the targets are identified. This in turn is dependent on the accuracy with which RCS is determined. To achieve accurate results, the exact Computational Electromagnetic (CEM) method - the Method of Moments (MoM) is used for computing the RCS of real size aircraft. The procedure to choose an optimal number of dominant natural resonant frequencies (NRFs) from a pool of NRFs for real size complex target is presented in this paper. The discrimination quantifying function `Risk' is shown to be effective in discriminating F5 aircraft - with and without missile attached underneath. The two targets have been successfully discriminated at all aspects, which is yet another challenge, establishing the aspect independent discrimination capability of the technique.

A radar for decisive target detection and tracking requires wideband, high return loss and high efficiency antenna array. In this paper, a 16 element staked-patch microstrip antenna array is presented at Ku-band with very low reflection coefficient for radar system. An aperture coupled feeding approach for a stack patch antenna is employed for wide bandwidth. A thin and low-loss tangent material, Taconic TLY-5, is used in the design of an antenna array to minimize the surface current loss and dielectric loss. Moreover, the antenna is designed with good impedance match, -30 dB, for high efficiency, by optimizing the stacked patches and utilizing reactive loading from u-slit on patch. For a low reflection coefficient antenna array over a wide bandwidth, an adequate feeding network consists of a compact and meandering stripline with metal-post around it is developed. The stripline configuration with metal-post minimizes crosstalk and lateral leakage. The feeding network developed has low reflection coefficient of -30 dB for the target band. The simulated feeding network loss is also low, 0.5 dB. The overall size of the 16 element array is compact, 295 mm x 30 mm (14λ x 1.425λ). The antenna array performance gives a reflection coefficient of -30 dB in the range of 14-14.5 GHz and total efficiency of 80%. The gain of the array is 21.54 dBi at 14.25 GHz.

In the letter, a compact dual-band Wilkinson power divider terminated with frequency-dependent complex impedance (FDCI) is proposed, for the first time. It is composed of two sections of coupled lines, two shunt transmission lines and a lumped resistor. By using the coupled lines, the FDCI at two bands can be matched. Further, the design equations for the proposed power divider are derived by using the even-odd mode decomposition technology. For verification, a prototype operating at 1.0 GHz and 1.8 GHz was designed, fabricated and measured with different terminal complex impedances at the two bands. The measured results show that the proposed WPD features equal power distribution, good impedance matching/isolation at two frequency bands.

In this article, a compact dual-band antenna system for LTE-M (700-900 MHz) and LTE-2500 dedicated to mobile handsets is presented. The system consists of a dual-band Planar Inverted-F-Antenna (PIFA) for LTE-M and LTE-2500 bands where this designed PIFA is frequency reconfigurable in the LTE-M band. Additionally, another PIFA is designed to cover the LTE-2500 band to enable Multiple-Input-Multiple-Output (MIMO) communication for this band. Frequency reconfiguration between 700 MHz and 900 MHz is performed by a varactor diode biased from the RF port using a decoupling circuit to separate DC and RF signals. The compactness of the system and the good isolation between the two antennas were obtained thanks to the study of the characteristic modes of the mobile phone chassis, where the ideal positions of the antennas can be easily obtained. A prototype of our system was fabricated where good frequency reconfiguration and good MIMO performance (TARC and envelope correlation) were achieved.

A myriad of ultra-wideband (UWB) 180˚ hybrids have been reported that operate at frequencies below 20 GHz. However, parasitics from printed circuit board (PCB) transmission lines become significantly more problematic as the frequency is extended to mm-wave frequencies. Here, abroadside coupled transmission line hybrid is investigated for operation at 12-67 GHz. It is shown that a parasitic time delay for the odd mode exists at the junction between coupled and uncoupled transmission lines. A heterogeneous multi-layer PCB stack-up is leveraged to compensate for the junction parasitics over an ultra-wide bandwidth. Measurements have an insertion loss between 2 and 12 dB across the band, < 1.5 dB amplitude balance, < 10˚ phase balance, and > 19 dB isolation.

In this work, a micro displacement sensor based on dual micro-cavities coupled to a photonic crystal waveguide is proposed. The defects are introduced to create a sharp resonance in the structure which makes it useful for detecting micro displacement changes. The sensing principle is based on the change of the output signal transmission with the change of the displacement of a moving part compared to a fixed part of sensor structure. The proposed structure reached a good sensitivity of 9.52a^-1.

This paper analyzes the variation trend of transmission coefficients of two electromagnetic interference filters with different structures in different temperature environments. Considering the influence of mutual-inductance between capacitors and temperature on parasitic parameters, we construct a wideband equivalent circuit model of electromagnetic interference filter and calculate the coefficient of the parameter as a function of temperature by measuring the parasitic parameters of common mode chokes (CMC) in different temperature environments. Because the wide range of selected temperature changes, it is necessary to divide the entire temperature range into two temperature segments and calculate the temperature coefficients respectively to ensure the accuracy of the data. Through the simulation and experiment, we have obtained the variation trend of the transmission coefficient of two kinds of structural electromagnetic interference filters under different temperature environments, and the trend shows that the attenuation performance of the filter rises first and then decreases with the increase of temperature, which verifies that the temperature will affect the performance of the filter.

Coupling in electronic devices may be a threat for the security of the information they process. Indeed, a current flowing into a conductor may radiate an electromagnetic field that will couple onto other conductors creating parasitic signals. If this current conveys sensitive information, its confidentiality may not be guaranteed. Moreover, depending on the amplitude of these parasitic signals, dysfunction may occur. It is thus valuable to assess the coupling effects in order to evaluate the probability that a current or a voltage reaches a given magnitude. This relevant quantity may be an input for a risk analysis process. In this study, we will focus on the study of couplings in reverberant cavities, and especially into the chassis of desktop computers. We will highlight that the Random Coupling Model (RCM) may be applied to determine statistical quantities related to induced currents or voltages between several ports placed inside a reverberant environment. Comparisons with experimental data, for several system configurations, show that the application of this model is relevant and allows to rapidly obtain the percentiles of the induced currents. At first, the coupling between two monopoles is studied, and then the coupling between printed circuit boards that are stacked together is investigated. Finally, the effect of adding broadband absorbers in casings is assessed.

A new approach to mitigate pilot contamination in massive MIMO systems is proposed in this paper. We consider two cells from the first tier of copilot cells of a cellular network where the base stations (BSs) are equipped with uniform linear arrays with hybrid beamforming adopted. We consider one cell as the cell of interest containing a typical desired user, and the other cell contains an interfering user sending data and contaminating pilot signals to the BS of the cell of interest. We derive a closed-form expression for the desired user's achievable rate as a function of the interfering user's angle of arrival (AoA). We model the ray propagation from the interfering user to the BS of the cell of interest and its related AoA as Gaussian distribution. Based on the model, we derive closed-form expressions for the pilot contamination level in the cell of interest, and for the desired user's data path gain estimation error due to pilot contamination. A perfect agreement is found between theoretical and Monte Carlo simulation results which show that when the interfering user's AoA is increased the pilot contamination level is significantly minimized, the desired user's data path gain estimation error also minimized, and hence its data rate is significantly increased. Moreover, we show in our analysis that the interfering user's AoA can be effectively controlled and increased by reducing the copilot cells' radius.

In this paper, the performance of a compact, multiband, and dual side printed microstrip patch antenna is introduced. The proposed antenna configuration is designed using a nested triangular patch and defected ground structure (DGS). A simple rectangular DGS is constituted in the ground plane, which helps to enhance the multiband characteristics of the antenna with its size. The proposed design exhibits compact size, better radiation, and reflection characteristics over a multiband frequency ranging from 1 GHz to 6 GHz. These entire bands are allied with various wireless communication services, such as GSM 1400 MHz and 1900 MHz, ISM, WLAN, Bluetooth, LTE, Wi-Fi, and GPS applications. The receiving Triangular Nested Patch (TNP) antenna offers omnidirectional radiation with 4.45 dBi gain and maximum return loss -34.31 dB at 3.75 GHz. Moreover, extraction of parameters has been presented in this paper with the variation of feed width and ground length. The proposed design shows the enhancement of gain and improved return loss. A comparative analysis has also been shown with the four different antennas parameters. Furthermore, this paper also presents the compact structure to cover efficient frequency ranging from 1400 MHz to 5.8 GHz for radiofrequency energy harvesting applications.

Nowadays compact terminal is one of the general requirements of modern wireless communication systems. The size of antenna limits further reduction of the structure size. To reduce size, a compact planar antenna based on Printed Circuit Board (PCB) is presented in this paper. This antenna has a new small-scale radiation coupling structure with a small hole and a matching element. This structure makes the ground structure of the circuit become an effective radiator through resonant coupling. This compact design avoids an independent big size radiator and the coupling structure over one quarter wavelength. Meanwhile, it can make the circuit have a good antenna matching effect at specific frequency by adjusting the lumped capacitance. Through the simulation and experiment, the design of antenna in 2.4 GHz ISM band is verified. The measurement results show that the antenna has 1.82 dBi gain and 151˚ beamwidth. It can be used in the compact wireless communication devices with advantages of low profile, adjustable frequency, and compact size.

In this paper, a dual-band dual-polarized magneto-electric (ME) dipole antenna with a dual-layer structure is proposed. The antenna consists of a dual-layer magneto-electric dipole, a Γ-shaped feeding line, and a rectangular box-shaped reflector. The dual-layer magneto-electric dipole is able to generate two resonant frequencies. Both simulated and measured results show that the antenna can obtain two wide impedance bandwidths of 47.5% (1.70-2.76 GHz) in lower frequency band and 30.2% (4.50-6.10 GHz) in higher frequency band with the reflection coefficients lower than -10 dB for both input ports. The isolation between ports is greater than 25 dB in the corresponding frequency band. The gains of the measured antenna are 8.5-9.7 dBi in the low frequency band and 7.5-8.5 dBi in the high frequency band, respectively.

A novel multifrequency printed monopole antenna applied to GSM, WLAN, and WiMAX standards in laptop devices is developed. The novelty of the proposed monopole antenna is the simple design without using any reactive components, expensive substrate, or any additional hardware to operate in multi-band frequencies for laptop applications. It is noteworthy that the dimensions of the proposed antenna structure is only 0.105λ × 0.05λ, at lower resonating frequency 1.8 GHz, thus attaining a height of only 9 mm above the system ground. This antenna mainly incorporates an `F'-shaped strip and a `C'-shaped strip together printed on an FR-4 substrate. The coaxial feeding results in the generation of three bands with measured impedance bandwidth spanned in the range of (1.74-1.87 GHz) in lower band (f_l), (2.40-2.50 GHz) in a medium band (f_m), and (5.12-6.06 GHz) in upper band (f_u). Furthermore, the aforementioned antenna exhibits excellent radiation performances including gain around 4-5 dBi followed by efficiency greater than 80% in all the operating bands. The simulated and measured results are found in good agreement which demonstrates the applicability of proposed antenna for GSM1800/WLAN/WiMAX applications in laptop devices.

In this communication, a compact two-port multiple input multiple output (MIMO) antenna with high isolation is presented for multiband applications. The size of the proposed structure is 0.15λ₀x 0.27λ₀ (λ₀, measured at lower frequency, is 2.95 GHz), and the antenna elements are separated by a distance of 0.04λ₀. The truncated partial ground offers good impedance performance with a fractional bandwidth of 136.5% from 2.95 to 15.65 GHz and covers the uninterrupted ultra-wideband (UWB), X and Ku band applications. High isolation of more than 25 dB is attained by placing parasitic elements between the antennas in a precise manner. The proposed structure is simulated, fabricated, tested, and verified practically. The radiation efficiency is more than 90% of the entire band. The peak gain values vary from 1.2 to 6.8 dB in the desired band, and its maximum value is 6.8 dB at 11.6 GHz. Diversity performance is also studied. The proposed structure offers an envelope correlation coefficient (ECC) of less than 0.04, diversity gain (DG) of greater than 9.996 dB, total active reflection coefficient (TARC) of below -10 dB, mean effective gain (MEG) of around -3 dB, and channel capacity losses (CCL) values are below 0.2 bits/sec/Hz. The measured and simulation results are in good concord.

A reconfigurable cylindrical dielectric resonator antenna with polarization diversity is proposed for S-band and C-band in this paper. An annular slot is used as the feeding aperture, which can not only excite two orthogonal modes (HEM^x_11δ and HEM^y_11δ) of the cylindrical dielectric resonator at 3.2 GHz, but also produce a 90˚ phase difference. Two switches, whose locations are carefully optimized, are used to control HEM^x_11δ being a phase-lagging or phase-leading component. Thus the antenna can achieve either left- or right-hand circular polarization (LHCP or RHCP) in S band, depending on the switch states. The higher order mode of HEM_21δ is also excited at 4.7 GHz for linear polarization (LP), regardless of the switch states. With the advantages of compact structure, simple biasing network and easy fabrication, this antenna can be widely applied to wireless communication systems, especially for polarization diversity applications.