We present a simple and straightforward approximate approach to removing resonant artifacts that arise in the material parameters extracted near half-wavelength resonances that arise from transmission/reflection (T/R) measurements on low-loss materials. In order to determine material parameters near one such λ/2 resonance, by means of the 1st-order regressions for the input impedance of the sample-loaded transmission line, we approximate the characteristic impedance of the sample-filled section that is, in turn, dependent either on the relative wave impedance in a coaxial transmission line or on the relative permeability in a rectangular waveguide case. The other material parameters are then found, supplemented with the refractive index obtained from the conventional T/R method. This method applies to both coaxial transmission line and rectangular waveguide measurements. Our approach is validated by use of S-parameters simulated for a low-loss magnetic material, and is also applied to determine the relative permittivity and permeability from S-parameters measured for nylon and lithium-ferrite samples. The results are discussed as compared to those from the well-known Nicolson-Ross-Weir (NRW) method and are experimentally compared to those from the Baker-Jarvis (BJ) method as well.

In this paper, an application of artificial neural network based on multilayer perceptron (MLP) model is presented for predicting the slot size on the radiating patch for improvement of the performance of patch antenna. Several performance affecting parameters like resonance frequencies, gain, directivity, antenna efficiency, and radiation efficiency for dual band frequency are observed with the variation of slot size. For validation of this work, a prototype X-shaped patch antenna is fabricated using glass epoxy substrate and its performance parameters are measured experimentally and have been found in good agreement with ANN and simulated values.

We present a flat lens design that provides focusing with no aberration. By profiling the refractive index of the lens to generate a spherical wavefront at the exit side of the lens, the transmitted fields converge at a specified focal point. The focusing is achieved using primarily the dispersion phenomenon. We show through numerical examples that focusing without aberration can be achieved at a specific frequency and that focusing is possible over a narrow range of frequencies providing that the dispersion is minimal. Additionally, we show that the same principle used to design the lens can be used to design flat reflectors with a focal point focusing.

For the GSOLT calibration algorithm of n-port vector network analyzers (VNA), the sensitivity coefficients for the S-parameters of the n-port device under test (DUT) are developed as functions of the S-parameter deviations of SOLT standards. By introducing the generalized flow graph of the 3n-term error model, analytic formulas for the S-parameter deviations of the n-port DUT with respect to the error terms have been deduced. In addition, expressions for the deviations of the error terms in regard to the nonideal calibration elements are given by a series of matrix operations. Finally, the analytic expressions of the sensitivity coefficients are concluded, which can be used for establishing the type-B uncertainty budget for S-parameter measurements.

This paper proposes a fusion technique of feature vectors that improves the performance of radar target recognition. The proposed method utilizes more information than simple monostatic or bistatic (single receiver) algorithms by combining extracted feature vectors from multiple (two or three) receivers. In order to verify the performance of the proposed method, we use the calculated monostatic and bistatic RCS of three full-scale aircraft and the measured monotatic and bistatic RCS of four scale-model targets. The scattering centers are extracted using one-dimensional FFT-based CLEAN and then used as feature vectors for a neural network classifier. The results show that our method has better performance than algorithms that solely use monostatic or bistatic data.

A low-cost dual-wideband active global navigation satellite system (GNSS) antenna is proposed for vehicle applications. An inverted shorted annular ring (ISAR) and a shorted annular ring (SAR) are used as radiation patches for low-angle multipath mitigation and operated respectively at 1164-1279 MHz and 1559-1610 MHz. To reduce the effect of the mutual coupling between the ISAR and SAR, meanwhile broaden the impedance bandwidth of the ISAR, defected ground structures are etched under the microstrip feed lines of the ISAR. Two trans-directional couplers are adopted to form orthogonal dual-feed networks of the ISAR and SAR for wideband circularly polarized reception. A combiner is adopted to merge two way signals into one way amplified by a wideband low noise amplifier with the proposed DC and RF collinear transmission technology. The experimental results show that the proposed antenna is better than the NovAtel GPS-703-GGG pinwheel antenna in terms of signal reception.

This paper critically reviews the electromagnetic advantages of altering the dielectric substrate section of the antenna as opposed to the conducting elements. Changing the dielectric has been used to improve the bandwidth, efficiency and gain of antennas. Heterogeneous substrates have also been employed to lower the effective permittivity, suppress surface waves for high indexed substrate materials and reduce mutual coupling. In the second half of this paper, 3-D printing has been used to create substrates with reduced material consumption for a lightweight flexible wearable antenna.

The imaging of targets embedded in a planar layered background media has been an important topic in subsurface and urban sensing. In this paper a fast and efficient tomographic algorithm for the imaging of targets embedded in a multilayered media is presented. The imaging algorithm is based on the first-order Born approximation and exploits the spectral multilayered media Green's function. The exploding reflection model is employed and then the Green's function is expanded in the spectral form to facilitate the easy implementation of the imaging algorithm with fast Fourier transform (FFT). The wave propagation effect due to the presence of the layered subsurface media is automatically taken into account in the imaging formulation through the multilayer media Green's function. The linearization of the inversion scheme and employment of FFT make the imaging algorithm suitable in several applications concerning the diagnostics of large probed domain and allow real-time processing. Representative examples are presented to show the effectiveness and efficiency of the proposed algorithm for radar imaging through multilayered media.

A right-handed circularly polarized (CP) substrate integrated waveguide (SIW)-based square ring-slot antenna array is proposed in this study. The array is composed of four elements and is based on a sequential rotation feeding technique to achieve wideband circularly polarization performance and high polarization purity. The feeding network for the array adopts SIW power divider having phase delay characteristic. In order to validate our design method, the antenna array is fabricated and measured. The measured impedance and axial ratio (AR) bandwidths are 8.5% (VSWR<2) and 6.1% (AR<3 dB), respectively, whereas the impedance and AR bandwidths for the element are 6.5% and 1.5%. It can be observed that this technique has significantly enhanced the AR bandwidth. Moreover, the antenna has a stable CP peak gain more than 12 dBi from 9.15 GHz to 9.5 GHz.

The present paper considers the connection between complex input impedance and the physical dimensions for planar ultra wideband (UWB) antennas. The first time the effect of both the actual radiator width and length for impedance behaviour is comprehensively presented. Also the effect of feed point dimensions on complex impedance is studied. The investigations involve both UWB single-resonant dipoles to cover bandwidth ≥ 500 MHz and a multi-resonant dipole for the entire Federal Communications Commission's (FCC) frequency band of 3.1-10.6 GHz. Lumped-element equivalent circuits are used identically with 3D antenna simulations in order to observe the corresponding impedance behaviour with the studied antennas. The used equivalent circuits consisting of series- and parallel-resonant stages are widely accepted in the open literature. The series-resonant circuit of equivalent is observed to have the analogue to the antenna feeding area. The physical dipole dimensions in terms of a length and width are connected to parallel-resonant part, which mainly determines the antenna input impedance. The resistance of a parallel-resonant stage behaves as the maximum value of real part of dipole impedance with an influence on bandwidth together with the ratio of parallel capacitance C and inductance L. The increase of the antenna physical width has an effect on bandwidth, because of the wider the antenna, the higher the capacitance in the antenna feed. Since the traditional dipoles are used for these studies, the results can be extended in several ways for other antenna types or, for instance, to verify the effect of body tissue, close to a wearable antenna.

The design of a novel low profile antenna is presented in this paper. By a cross-shaped structure shorted to the ground plane through shorting probes, the size reduction is achieved. A top-loading ring-disc is successfully employed to broaden the impedance bandwidth. Moreover, with the uniformly-arranged shorting pins and a circular sleeve structure placed on the ground, a good omnidirectional performance in the horizontal plane is obtained. An antenna prototype has been implemented and characterized. A measured impedance bandwidth for VSWR ≤ 2 of about 135% ranging from 1500 to 7800 MHz is achieved, and a monopole-like radiation pattern is also produced. The height of the proposed antenna is very low with 0.07λ tall. The proposed antenna is very suitable for indoor base station and the UWB applications.

Splitting a cylinder dielectric resonator into four uniform quarters generates a new dielectric resonator antenna(DRA) shape, which is named a quarter volume of cylinder dielectric resonator antenna (QVCDRA) in the paper. On the basis, a novel compactthree-port dielectric resonator antenna with reconfigurable radiation pattern is presented for WLAN systems at 5.2 GHz. A -10 dB impedance bandwidth of 16.20%,covering the frequency range from 4.75 GHz to 5.54 GHz, is obtained with an isolation of lower than -19 dB. The structure consists of three QVCDRAs that arrange evenly around Z axis, and as a result possesses the advantage of compact structure, wide impendence bandand reconfigurable radiation patterns. The volume of the proposed three-port DRA without ground plane is only 0.0216 (is the dielectric wave length at the central operation frequency). The proposed antenna is analyzed in detail. Antenna prototype is fabricated and tested. The simulation and test results are in good agreement.

A compact planar monopole UWB antenna with quadruple band-notched characteristics is analyzed and presented. By introducing a C-shaped slot, nested C-shaped slot in the radiating patch and U-shaped slot in the feed line, quadruple band-notched characteristics are achieved at frequencies of 2.5, 3.7, 5.8 and 8.2 GHz. The proposed antenna has been fabricated and tested. Measured impedance bandwidth of the antenna is 2.35-12 GHz, which covers Bluetooth and UWB band, for VSWR < 2 and also has four stop bands of 2.44-2.77, 3.42-3.97, 5.45-5.98 and 8-8.68 GHz, for VSWR > 2, for rejecting 2.5/3.5 GHz WiMAX, WLAN and ITU 8 GHz band signals, respectively. The average gain of this antenna is 4.30 dBi with a variation of ±1.8 dBi over the whole impedance bandwidth. Significant gain reduction over the rejected band is also observed. The antenna shows good omnidirectional radiation patterns in the passband with a compact size of 40 mm × 34 mm.

This paper discusses the electromagnetic characteristics of a stratified metamaterial structure placed in fractional dimension space. Reflection and transmission coefficients for plane wave incident on multilayered structure in D-dimensional space are computed. Transfer matrix method is used to study the behaviour of different planer multilayered periodic metamaterial structures. The results are compared for integer and fractal dimensional spaces for both the cases of normal and oblique incidences. Classical results are recovered for integer dimensions. This work provides solution for examining the electromagnetic fields and waves in multilayered structures at fractal interfaces.

In order to enhance the capacity of an optical-interconnect link with a single wavelength carrier, multimode spatial-division multiplexing (SDM) technology has been attracted lots of attention. For a mode-multiplexed optical-interconnect link, the functionality elements become quite different from the conventional ones because multiple modes are involved. In this paper we give a review and discussion on multimode photonic integrated devices for mode-multiplexed optical-interconnect. First light propagation and mode conversion in tapered waveguides as well as bent waveguides is discussed. Recent progresses on mode converter-(de)multiplexers are then reviewed. The requirement of some functionality devices used for mode-multiplexed optical-interconnects is also discussed. In particular, the fabrication tolerance is analyzed in detail for our hybrid demultiplexer, which enables mode-/polarization-division-(de)multiplexing simultaneously.

This paper presents a technical which improves energy efficiency of AC rotating machines by using Grain Oriented (GO) steel at stator core instead of Non Oriented (NO) steel. The losses of GO steel are less important only if the magnetic flux circulates along the rolling direction; consequently it is rarely used in AC machines where the magnetic flux rotates. By stacking many shifted GO laminations of AC machine stator, the flux pass from one lamination to another, and the core losses are reduced. A lot of experimentations have been done with unidirectional field, rotating field and with real induction machines. They show important improvements with GO shifted steel. The efficiency difference between a classical 10kW induction machine and a modified machine with GO stator is more than 2 points. Moreover, the no-load current and so the reactive power are smaller. This technical creates environmental and financial gains.

A special class of metamaterials known as hyperbolic media allow the propagation of large classes of novel monochromatic and pulsed localized waves. Illustrative explicit solutions are given of ``accelerating'' oblique Airy beams, as well as nondiffracting and nondispersive spatiotemporally localized ``all-speed'' X-shaped and MacKinnon-type waves.

In this paper, a 42 GHz frequency synthesizer fabricated with 0.13 μm SiGe BiCMOS technology is presented, which consists of an integer-N fourth-order type-II phase locked loop (PLL) with a LC tank VCO and a frequency doubler. The core PLL has three-stage current mode logic(CML) and five stage true single phase clock (TSPC) logic in the frequency divider. Meanwhile, a novel balanced common-base structure is used in the frequency doubler design to widen the bandwidth and improve the fundamental rejection. The doubler shows a 41% fractional 3 dB bandwidths with a fundamental rejection better than 25.7 dB. The synthesizer has a maximum output power of 0 dBm with a DC power consumption of 60 mW. The worst phase noise at 100 kHz, 1 MHz and 10 MHz offset frequencies from the carrier is -71 dBc/Hz, -83 dBc/Hz and -102.4 dBc/Hz, respectively.

The far-field pattern symmetry of the cavity backed planar spiral antenna is analyzed. We discover that the back radiation of the planar spiral and the cavity effects degrade the pattern symmetry. To improve the pattern symmetry, an improved method to reduce the back radiation is proposed. Then a novel antenna configuration is designed. The center section of the planar spiral is replaced with a conical spiral. So the back radiation at higher frequency band can be restrained. The broadside gain, axial ratio and pattern symmetry are compared. The results show that this novel configuration can achieve better far-field symmetry at a wider band.

This paper investigates the effects on received mutual coupling of λ/2 dipole arrays placed near real-earth. As a rule of thumb, estimation of mutual coupling can be divided in two regions of antenna height that is very near ground 0 < h < λ and fairly freespace region h ≥ λ. The receiving antenna mutual coupling remains fairly unaffected from ground conductivity, when antenna height h ≥ λ. Both vertical and horizontal polarization cases showed the same trend. Investigation of effects of nearness of good-ground to the array on DOA estimation revealed that for azimuth DOA estimation, the proposed method of removing mutual coupling works well even for near ground.