Bandwidth improvements using ground slots for compact UWB microstrip-fed antennas

The paper studies the method of using a ground slot for bandwidth improvement of compact ultra-wide band (UWB) antennas with microstrip line feed. Slots of different shapes such as triangular, rectangular, partially circular and hexagonal, placed on the ground plane under the feed line of the radiator are studied for impedance matching. The effects of the slots on the performances of the antennas, in terms of impedance bandwidth, radiation pattern, gain, and efficiency, are studied. Results of simulation tests show that a ground slot with proper dimensions placed under the feed line can improve the impedance matching and hence increase the bandwidth without affecting much the performance of the antenna. Results of studies also show that, by using a hexagonal slot on the ground plane under the feed line, a patch antenna with a compact size of 35mm × 23mm can achieve a bandwidth of 3.1-16.3 GHz for S 11 < -10 dB. Moreover, it has a stable omnidirectional radiation pattern across the whole bandwidth and achieves an average gain of 2.8 dBi and an average efficiency of about 88% across the UWB.published_or_final_versio

Compact MIMO antenna for portable devices in UWB applications

A compact multiple-input-multiple-output (MIMO) antenna with a small size of 26× 40mm2 is proposed for portable ultrawideband (UWB) applications. The antenna consists of two planar-monopole (PM) antenna elements with microstrip-fed printed on one side of the substrate and placed perpendicularly to each other to achieve good isolation. To enhance isolation and increase impedance bandwidth, two long protruding ground stubs are added to the ground plane on the other side and a short ground strip is used to connect the ground planes of the two PMs together to form a common ground. Simulation and measurement are used to study the antenna performance in terms of reflection coefficients at the two input ports, coupling between the two input ports, radiation pattern, realized peak gain, efficiency and envelope correlation coefficient for pattern diversity. Results show that the MIMO antenna has an impedance bandwidth of larger than 3.1-10.6 GHz, low mutual coupling of less than-15 dB, and a low envelope correlation coefficient of less than 0.2 across the frequency band, making it a good candidate for portable UWB applications. © 2013 IEEE.published_or_final_versio

Polaronic effect in the x-ray absorption spectra of La1-x Ca x MnO3 manganites.

X-ray absorption spectroscopy (XAS) is performed to study changes in the electronic structures of colossal magnetoresistance (CMR) and charged ordered (CO) La1-x Ca x MnO3 manganites with respect to temperature. The pre-edge features in O and Mn K-edge XAS spectra, which are highly sensitive to the local distortion of MnO6 octahedral, exhibit contrasting temperature dependence between CMR and CO samples. The seemingly counter-intuitive XAS temperature dependence can be reconciled in the context of polarons. These results help identify the most relevant orbital states associated with polarons and highlight the crucial role played by polarons in understanding the electronic structures of manganites

Procurement innovation: perspectives from Chinese international construction companies

The international construction business is witnessing a trend that companies deliver projects through the adoption of innovative procurement systems (e.g. Building Operate Transfer, Public Private Partnership). By devising innovative procurement systems, it is possible to realise construction projects that are difficult for traditional procurement methods, to develop competitive advantages for companies, and ultimately, to deliver value to the society. Notably, Chinese companies are making impressive inroads into the international construction market through enhancing their competitiveness. However, little we know about how Chinese international construction companies (CICCs) perceive procurement innovation and how it relates to their recent success. This research aims to capture their perspectives towards procurement innovation by interviewing nine key decision-makers of CICCs and experts in this area. It is found that CICCs are gradually adopting procurement innovation as a competitive strategy. Unlike the traditional life-or-death competition, competing through procurement innovation can make more projects possible; the emergence of CICCs, in particular their strengths, can be encouraged to deliver more projects and value in the international construction market. This research not only provides CICCs with insights into the procurement innovations in the construction sector, but also enables other companies to know CICCs with which they might compete or collaborate in the near future.published_or_final_versio

Design of a printed multiband MIMO antenna

A multiband MIMO antenna using planar technology is proposed for next generation mobile communication system. The antenna consists of two symmetrical monopole elements printed in parallel to each other at the upper and lower corners of a printed-circuit board (PCB) with a size 50×110 mm2 which is similar to the side of a mobile phone. The two monopoles have two branch strips to generate two frequency bands. By using a parasitic element in each monopole, a much enhanced bandwidth in the upper band can be obtained. A lumped-impedance network is designed to enhance matching at the input ports for the two antenna elements. Computer simulation is used to study, design and optimize the antenna. Results indicate that the proposed MIMO antenna has a very bandwidth enough to cover the LTE (lower band), DCS1800, PCS1900, UMTS-2100, Wibro Band, 2.4G-WLAN, and Wimax (upper band) systems. To enhance the isolation between the two monopole elements within the desirable frequency bands, a slit is cut in the middle on the PCB ground. The MIMO antenna a very low profile and low cost which makes the design very attractive for mobile phone applications. © 2013 EurAAP.published_or_final_versio

Frequency-Reconfigurable Antenna using Metasurface

A frequency-reconfigurable antenna designed using metasurface (MS) to operate at around 5 GHz is proposed and studied. The frequency-reconfigurable metasurfaced (FRMS) antenna is composed of a simple circular patch antenna and a circular MS with the same diameter of 40 mm (0.67 λ) and implemented using planar technology. The MS is placed directly atop the patch antenna, making the FRMS antenna very compact and low profile with a thickness of only 3.048 mm (0.05 λ). The MS consists of rectangular-loop unit cells placed periodically in the vertical and horizontal directions. Simulation results show that the operating frequency of the antenna can be tuned by physically rotating the MS around the center with respect to the patch antenna. The MS placed atop the patch antenna behaves like a dielectric substrate and rotating the MS changes the equivalent relative permittivity of the substrate and hence the operating frequency of the FRMS antenna. Measured results show that the antenna has a tuning range from 4.76 to 5.51 GHz, a fractional tuning range of 14.6%, radiation efficiency and a realized peak gain of more than 80% and 5 dBi, respectively, across the tuning range. © 2013 IEEE.published_or_final_versio

Dual-band MIMO antenna using double-T structure for WLAN applications

Session - Interactive 2.3: Multi-Band AntennasThe Conference program's website is located at http://www.iwat2014.org/index.php/program/detailed-programA dual-band multiple-input-multiple-output (MIMO) antenna is proposed for the wireless-local-area-network (WLAN) applications in the 2.4-GHz and 5.2-GHz bands. The antenna consists of two double-T monopole elements with microstrip-fed and symmetrically placed on a substrate. To enhance isolation between the two monopole elements, three slots are cut on the ground plane on the other side of the substrate. The longer slot is used for better isolation in the 2.4-GHz band, while the two shorter slots are used for the 5.2-GHz band. Simulation and measurement are used to study the antenna performance in terms of S parameters, radiation patterns, realized gain, efficiency, and envelope correlation coefficient. Results show that the MIMO antenna has the two operation bands of 2.20-2.75 GHz and 5.09-5.50 GHz with mutual coupling of less than -15 dB and envelope correlation coefficient of less than 0.1, making it a good candidate for WLAN applications.published_or_final_versio

Isolation improvement using CMRC for MIMO antennas

In this paper, a compact microstrip resonant cell (CMRC) is proposed to improve isolation of antenna elements in the design of multiple-input multiple-output (MIMO) antennas. The MIMO antenna used for studies consists of two symmetrical L-shaped planar inverted-F antenna (PIFA) elements placed at a distance of 16.2 mm on a printed-circuit board (PCB). A single-layer CMRC is etched on the PCB between the PIFA elements to improve isolation between them. Computer simulation is used to study and design the MIMO antenna. Results show that the CMRC can increase isolation between the two PIFA elements by 10 dB in the 2.4-GHz WLAN band. The envelope correlation coefficient (ECC) is about 0.0005 to 0.0035 over the frequency band.postprin

Sharpening Competitive Edge through Procurement Innovation: Perspectives from Chinese International Construction Companies

The international construction business is witnessing a trend towards the delivery of projects through the adoption of innovative procurement systems, which allow companies to gain competitive advantages and to potentially deliver enhanced value to society. Notably, Chinese companies are making steady inroads into the international construction market by enhancing competitiveness. However, we know little about the extent to which Chinese international construction companies (CICCs) perceive procurement innovation and how this factor may relate to their recent success. This research aims to fill the void based on interviews with nine CICC key decision‐makers and experts in this area, and the capturing of their perspectives. It is found that CICCs are gradually adopting procurement innovation as a competitive strategy. Although procurement innovation is conducive to competitive advantage in the long run, CICCs have to pay the cost of entering the new market. Thus a “wait‐and‐see” attitude exists in respect of a long term vision. Unlike the traditional win‐lose competitive bidding system, competing through procurement innovation can lead to larger, more suitable market presence. By succinctly describing the CICC story in the international market this research not only provides CICCs themselves with insights into current procurement innovations existing within the construction sector, but also enables other companies to understand the nature of CICCs with which they might compete or collaborate in the near future.postprin

Systemic lupus erythematosus (SLE) is associated with telomerase activation

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