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.

A miniaturized trans-directional (TRD) coupled line coupler comprises series inductors and capacitor loaded coupled lines is proposed in the paper. Series inductors are added to the periodically loaded coupled lines for further miniaturization of volume. A novel equivalent circuit is presented and theoretically analyzed. Test circuits for the miniaturized and conventional 3-dB TRD couplers were designed to operate at 1.6 GHz and fabricated using printed circuit board (PCB) technology. Samples have been measured, and comparisons in terms of volume, schematic simulation results and measurement results between the miniaturized and conventional 3-dB TRD couplers have been made to validate the proposed structure. Results show that the proposed miniaturized TRD coupler achieves a size reduction of 47.6% compared to the conventional TRD coupler with similar performances.

In this article, a compact ultra-wideband (UWB) planar monopole antenna with the triple notched band is proposed. The antenna consists of a semicircular radiating patch and a modified ground plane with two bevels at upper edge. By etching two round shape slots in radiating patch the notch characteristics are achieved at WiMax band (3.3-3.7 GHz) and WLAN band (5.15-5.875 GHz). In order to realize notch band at X-band downlink satellite communication band (7.1-7.76 GHz) a pair of rotated V-shape slot are etched on the ground plane. The measured operating impedance bandwidth of proposed antenna ranges from 2.9 to 10.9 GHz having return loss less than 10 dB with triple notched bands. The proposed antenna exhibits a nearly omnidirectional radiation pattern in the H-plane, and a dipole-like radiation pattern in the E-plane for the ultra-wideband. The effects of each individual slot on band-notch characteristics are also investigated. The measured gain of the proposed triple band notched antenna is relatively stable across the operating frequency band except notched bands and thereby making the proposed antenna suitable for practical UWB applications. Proposed antenna has a compact size of 27x25 mm².

This paper proposes a novel signal processing approach to thermal non-destructive testing by incorporating Gaussian window function onto the linear frequency modulated incident heat flux to achieve better pulse compression properties. The present work highlights a finite element analysis based modeling and simulation technique in order to test the capabilities of the proposed windowing scheme over the conventional frequency modulated thermal wave imaging method. It is shown that by using Gaussian weighted chirp thermal stimulus, high depth resolution can be achieved.

Partial Discharge detection techniques strive to ensure a safe and reliable power network by preventing power failure. In this work, electromagnetic sensing of partial discharge, in air-insulated medium voltage switchgear (Type D24-121114 of Driescher) is considered. The partial discharges are approximated by Gaussian sources. A versatile broadband sensor for detecting two major types of partial discharge was designed and optimized. The antenna has low return loss and high gain over the frequency band of corona discharge, 0.75-0.9 GHz and dry band arching, 1.25-1.4 GHz. The horn antenna is incorporated into the medium voltage switchgear for detecting partial discharges. The analysis of the electromagnetic field distributions generated by partial discharges in switchgear is coupled with the sensing efficiency of the horn antenna. The results indicate a good correlation between the intensity, location and frequency band of partial discharge and their sensing. This study provides the foundation for a dual band detection system of partial discharge in switchgear systems.

A broadband circularly polarized (CP) slot antenna array fed by a coplanar waveguide (CPW) is proposed. A fan-shaped feed line and three L-shaped grounded strips are embedded in the square slot antenna element to enlarge the bandwidth. Simulated results show that the antenna element can obtain a wide impedance bandwidth with -10 dB reflection coefficient covering 1.7-6.3 GHz (about 115% relative bandwidth) and 3 dB axial ratio (AR) bandwidth covering 2.6-5.2 GHz (about 66%). Using four elements with sequential phase feed, the measured impedance bandwidth and axial ratio bandwidth of the antenna array can be enhanced to 105% (1.65-5.35 GHz) and 71.3% (2.3-4.85 GHz), respectively. Good radiation characteristics with the peak gain of 10.8 dBic over the operating band can be obtained.