Some new focusing properties of time-domain ultra wide band (UWB) focusing array antennas are presented. The large current radiator (LCR) is considered as the UWB antenna element. Each LCR is replaced by a set of infinitesimal dipoles modeling both the near field and the far field patterns of the antenna element and the coupling between the elements. Several antenna arrays with different sizes and number of elements are modeled. It is shown that similar to narrow band antennas, the actual maximum field region shifts from the intended focus region towards the antenna aperture.

In this paper, we propose a microstrip filter balun adopting double-sided parallel-strip line (DSPSL) with a conductor plane inserted in the middle of the substrate. Fed by the DSPSL at input port, two microstrip filters on top and bottom layers are excited simultaneously, with the frequency-independent out-of-phase feature obtained between two output ports. The proposed filter balun exhibits excellent performance with good frequency selectivity because of multiple transmission zeros generated by a new coupling scheme. Finally, a filter balun sample is designed and fabricated, and good agreement is obtained between its measured and simulated S-parameters.

Interference and multipath is one of the current issues in a wireless communication system, with complicated scenarios of environment especially in urban areas with a high number of users. Introducing smart antenna systems at the base station can contribute to reducing interference and improve quality of service. This paper proposes and explores the application of artificial immune system and negative selection algorithm to the prototype of smart antenna, where the proposed smart antenna is a hexagonal structure with 6-elements of the antenna array and working in LTE band at 2.6 GHz. Initial testing was done to define the RSSI value by calculating the average of the signal then comparing RSSI value defined by implementing artificial immune algorithm. To proof and determine actual RSSI signal received, a test in an anechoic chamber is conducted as reference that assumes free interference and multipath then compared to both of results. X-Bee module was used for transmitter and receiver in system at 2.4\,GHz band, and the proposed system prototype with hexagonal structure also used dual ARM microprocessor. Negative selection algorithm is applied in smart antenna programming to define actual values of receiving signal and angle of arrival. Every beam of the antenna were installed with an X-Bee module then connected to microprocessors, with an LED installed at each of the antenna as an indicator of beam switching or angle of arrival signal.

Nowadays low profile passive array planar antennas are being more and more used substituting traditional parabolic antennas in satellite communications. To achieve a good efficiency in printed arrays it is necessary to use a low losses network. A shielded suspended stripline is proposed in this paper. The main aim of this network is to distribute the power among subarrays in an array antenna with minimum losses. Several vertical transitions to subarrays are shown besides some network designs for square arrays at X band.

novel tapered slot antenna (TSA) with 3.5/5.5 GHz dual band-notched characteristics for ultra-wideband (UWB) radios is proposed in this paper. To realize dual band-notched characteristics at the TSA, we employ (a) a pair of nested C-shaped stubs beside the feed line and (b) a broadband microstrip-to-slot-line transition with an Archimedean spiral-shaped slot. The proposed antenna has been successfully simulated, implemented, and measured. An equivalent circuit model of the proposed antenna is also presented to discuss the mechanism of the dual band-notched TSA. The measured data for the optimized case show the bandwidth for the VSWR < 2 to be 9.2 GHz (from 2.4 to 11.6 GHz) with two notched bands of 3.1-4.0 GHz (WiMAX band) and 5.1-6.2 GHz (WLAN band), respectively. The measured electrical parameters of the proposed antenna and its radiation patterns show excellent performance with good pulse handling capabilities. Also, the 3.5/5.5 GHz dual band-notched characteristics are achieved without increasing the size of the single band-notched TSA reported previously.

In this paper, an octave bandwidth Doherty power amplifier (DPA) using a novel combiner is presented. The fundamental bandwidth limitation of the load modulation concept of a conventional Doherty structure is solved based on the proposed combination method. For verification, an octave bandwidth asymmetric Doherty architecture is implemented by using gallium-nitride (GaN) HEMT Cree CGH40010 and CGH40025 devices in the carrier and peaking amplifiers, respectively. The carrier and peaking amplifiers are designed to achieve optimal operation with 25 Ω load and source impedances. The reduced load and source impedances simplify the matching circuits for broadband operation. Key building blocks, including the proposed combiner, carrier and peaking amplifiers as well as the 50/25 Ω input power divider, are outlined. The measurement results represent higher than 37% and 52% drain efficiencies in 6 dB load modulation region across the frequency range from 0.85 to 1.85 GHz and 0.90 to 1.60 GHz, respectively. The implemented Doherty amplifier represents acceptable linearity across the whole operation frequency range. In two-tone signal characterization, the implemented DPA performs with a drain efficiency of 55% and an inter-modulation distortion (IMD) of -30 dBc at an average output power of 41.2 dBm at the center operation frequency of 1.35 GHz. In order to observe wideband signal characterization, a single carrier wideband code-division multiple access (W-CDMA) signal with a peak-to-average power ratio (PAPR) of 6.5 dB is applied and a drain efficiency of 51% with an adjacent-channel leakage ratio (ACLR) of -31 dBc is achieved at an average output power of 38.4 dBm.

This paper presents analytical formulas, based on the "thin wire model", for calculating the ELF (Extremely Low Frequency) sub-sea electromagnetic field produced by a submarine power cable. Two different models are studied: the first and simpler one (already present in literature) is based on the infinite sea model while the second and more realistic one, that we propose, takes into account of the seabed presence with the sea considered having finite depth. The shielding effect produced by cable sheath and armouring is taken into account by means of suitable shielding factors. Some examples of application of the two models are shown and the relevant results are compared between them.

A cavity backed conformal broadband compact hexagonal patch antenna is proposed that is fed using a co-axial probe. This horizontally mounted shorted antenna yields vertical polarization. The antenna yields 9.52% bandwidth centered around 1.05 GHz. The simulated results of electrical parameters of this antenna are in good agreement with measured ones. This vertically polarized antenna can be used for IFF airborne applications.

This paper discusses the application of computational electromagnetics (CEM) for electromagnetic compatibility (EMC) problems of integrated circuits (ICs). It is known that the application of CEM is versatile in solving a wide range of problems. This paper focuses on the electromagnetic study of quad flat non-lead (QFN) packaged ICs, one monolithic microwave integrated circuit (MMIC) and another radio frequency integrated circuit (RFIC), from the individual chip to system in package (SiP). Full-wave electromagnetic technique is conducted in the modelling and simulation. Both chips are found producing radiated emissions in horizontal directions as omnidirectional antennas at working frequencies and then directional at resonance frequencies.

Fractal antennas have undergone dramatic changes since they were first considered for wireless systems. Numerous advancements are developed both in the area of fractal shaped elements and fractal antenna array technology for fractal electrodynamics. This paper makes an attempt of applying the concept of fractal antenna array technology in the RF regime to optical antenna array technology in the optical regime using nonlinear array concepts. The paper further discusses on the enhancement of nonlinear array characteristics of fractal optical antenna arrays using nonlinearities in coupled antennas and arrays in a conceptual manner.

This paper presents the design and analysis of permanent magnet (PM) thrust bearing made up of three ring pairs for five degrees of freedom of the inner rings (rotor rings). The arrangement pattern of rings in PM bearing is considered in two ways: conventional structure and Halbach structure. The simplified three dimensional (3D) mathematical models employing Coulombian approach and vector method are used to design the bearing. MATLAB codes are written to evaluate the axial force, stiffness and moments in both the structures for five degrees of freedom, thereby the effect of axial, radial and angular displacements of the rotor on the aforementioned characteristics is addressed. The results of the mathematical model are validated by the results of 3D Finite Element Analysis (FEA) and experiments. It is observed that, the conventional structure seems to be more sensitive to the angular displacement, as the percentage decrease in force and stiffness is more with respect to angular displacement than the Halbach structure. The effect of angular displacement of the rotor on the performance of bearing in both the structures is crucial.

A novel shaped of printed monopole antenna with a koch fractal technique is presented in this paper. The ultra-wide bandwidth (UWB) antenna is composed of a modified ground plane with two independently elements as cross and Egyptian arc shapes to improve the antenna bandwidth. PIN diode is used to connect or disconnect the circular arc between two bands to switch frequencies from 500 to 2500 MHz and from 4 to 10 GHz. This implemented antenna effectively support personal communication system (PCS 1.85-1.99) GHz, universal mobile telecommunication system (UMTS 1.92-2.17) GHz, wireless local area network (WLAN), which usually operate in the 2.4 GHz (2.4-2.484 GHz) and 5.2/5.8 GHz (5.15-5.35 GHz/5.725-5.825 GHz) bands, mobile worldwide interoperability for microwave access and WiMAX, which operate in the range from 2.305 to 2.360 GHz, from 2.5 to 2.69 GHz and from 5.25 to 5.85 GHz bands. The properties of the antenna as reflection coefficient, efficiency, radiation patterns and gain are simulated and approved by the experimental results.

In this paper, a compact microstrip wideband bandpass filter (BPF) based on square ring loaded resonator (SRLR) is proposed. The SRLR is formed by loading a pair of bent open-stubs outside the diagonal corners of a square ring, which generates three split degenerated modes. The first two split modes form a dominant wideband passband. By introducing another pair of loaded open-stubs, the third split mode is moved into the passband to achieve an extra bandwidth for the wideband passband. Measured results show that this proposed BPF has a 3 dB fractional bandwidth of 69%, and the insertion loss of the BPF is less than 1.0 dB.

Because the oversized, ultra short-range and arbitrary-shape goals cannot be imaged by Fourier transform algorithm, a Boundary Element Method(BEM) is presented for short-range millimeter wave holographic imaging.Through the discrete boundary integral equation, the discrete electromagnetic fields on the source surface and holographic surface are obtained. They are linked by a transfer matrix. Finally, the discrete electromagnetic fields obtain target holographic image. Due to the complexity of the transfer matrix, the Distributed Source Boundary Point Method (DSBPM) is introduced to calculate it, which greatly simplifies the calculation process. The simulation experiments of three-dimensional hemisphere imaging show the sensitivity of the imaging algorithm to test error, and regularization method has been proposed. The actual measurement of the four small metal balls verifies the validity of the imaging algorithm for large target imaging. The imaging results show that holographic imaging of the boundary element method can obtain high resolution and high amplitude accuracy.

A systematic method for the efficient design of narrowband filters founded on the extraordinary transmission via single fishnet structures (SFSs) is presented in this paper.~Essentially, due to its strong resonant behavior, this phenomenon is proven suitable for the implementation of high-$Q$ devices.~The new design formulas are derived through the combination of full-wave numerical simulations and curve fitting algorithms. Also, adequate mathematical criteria are defined for the evaluation of the filters' linear performance, indicating that the transmitted electromagnetic waves remain practically undistorted in the frequency band of interest. Then, by exploiting the previously developed relations, proper correction factors are introduced in the existing SFS equivalent circuit expressions, which hardly increase the overall computational complexity. This quantitative modification leads to an enhanced characterization of SFSs, as key components for diverse applications. Finally, several limitations as well as possible ways of extending the featured algorithm to more complicated structures and higher frequency bands are briefly discussed.

Radar features from higher order motions of a wind turbine undergoing rotation are studied. Mathematical models for the motions are proposed and used to simulate the joint time-frequency (JTF) and inverse synthetic radar aperture (ISAR) characteristics of the motions. The motions are studied for an isolated turbine as well as for a turbine rotating above a ground. Selected motions are corroborated by laboratory model measurements.

This paper presents a one-wavelength loop antenna fed by an inductively coupled loop for on-body applications. An equivalent circuit for the inductively coupled loop antenna is proposed to synthesize the antenna system with a microchip. The designed tag is printed on a PVC substrate and placed close to a four-layer stratified elliptical cylinder human model. The card-type tag measures 85.5 × 54 × 0.76 mm³ and is suitable for use on a student ID card for a broad range of applications. The impedance bandwidth of the inductively coupled loop tag antenna is 60 MHz (880-940 MHz, 6.6%), which covers the operating UHF bands in U.S. and Taiwan. The measured reading distance ranges from 2.7 to 5.7 meters when placed at different positions on the chest of a human body in the open site.

We present the dispersion and local-error analysis of the twenty-seven point local field expansion (LFE-27) formula for obtaining highly accurate semi-analytical solutions of the Helmholtz equation in a 3D homogeneous medium. Compact finite-difference (FD) stencils are the cornerstones in frequency-domain FD methods. They produce block tri-diagonal matrices which require much less computing resources compared to other non-compact stencils. LFE-27 is a 3D compact FD-like stencil used in the method of connected local fields (CLF) [1]. In this paper, we show that LFE-27 possesses such good numerical quality that it is accurate to the sixth order. Our analyses are based on the relative error studies of numerical phase and group velocities. The classical second-order FD formula requires more than twenty sampling points per wavelength to achieve less than 1% relative error in both phase and group velocities, whereas LFE-27 needs only three points per wavelength to match the same performance.

A Neural Network is a simplified mathematical model based on Biological Neural Network, which can be considered as an extension of conventional data processing technique. In this paper, an Artificial Neural Network (ANN) based simple approach is proposed as forward side for the design of a Circular Fractal Antenna (CFA) and analysis as reverse side of problem. Proposed antenna is simulated up to 2nd iteration using method of moment based IE3D software. Antenna is fabricated on Roger RT 5880 Duroid substrate (High frequency material) for validation of simulated, measured and ANN results. The main advantage of using ANN is that a properly trained neural network completely bypasses the complex iterative process for the design and analysis of this antenna. Results obtained by using artificial neural networks are in accordance with the simulated and measured results.

Imaging techniques based on time reversal method are particularly suitable for detection of targets embedded in a strongly scattering media. Generally in time reversal imaging technique we need to know the Green's function of the medium and the exact locations of the transmitter and receiver antennas. We introduce a target imaging method in which imaging is made with an arbitrary placement of the transmitting or receiving antennas. Numerical simulations are used to illustrate the capabilities of the proposed algorithms in different scenarios. We use the two-dimensional finite difference time domain method in our simulations. The numerical simulations are done for a typical through-the-wall scenario. We also present results in which the same method is used for tracking targets behind the wall.