Slot Resonators for Characterization of Dielectrics at Microwave Frequencies

Open planar resonators like single and stacked microstrip resonators were used in the past for the measurement of dielectric constants and thicknesses of lossy and lossless dielectrics at microwave frequencies [1–3]. With a large width, the microstrip resonator effectively acts as a planar antenna in which case the fringing field is significant for the two slots at the two ends of the resonator and the resonator Q-factor is low. One of the limitations of the microstrip resonator is its spatial resolution which is determined by the size of the resonator. It is envisaged that this problem can be overcome by the use of planar slot resonators, Fig.1. Furthermore, compared to the microstrip-fed microstrip resonator, a microstrip-fed planar slot resonator would provide a better isolation between the feed and the material under test

Directional emission of light from a nano-optical Yagi-Uda antenna

The plasmon resonance of metal nanoparticles can enhance and direct light from optical emitters in much the same way that radio frequency (RF) antennas enhance and direct the emission from electrical circuits. In the RF regime, a typical antenna design for high directivity is the Yagi-Uda antenna, which basically consists of a one-dimensional array of antenna elements driven by a single feed element. Here, we present the experimental demonstration of directional light emission from a nano-optical Yagi-Uda antenna composed of an array of appropriately tuned gold nanorods. Our results indicate that nano-optical antenna arrays are a simple but efficient tool for the spatial control of light emission.Comment: 4 pages, including 4 figure

Channel gain for a wrist-to-arm scenario in the 55-65 GHz frequency band

Wireless communication on the body is expected to become more important in the future. This communication will in certain scenarios benefit from higher frequencies of operation and their associated smaller antennas and potentially higher bandwidths. One of these scenarios is communication between a wristband and wearable sensors on the arm. In order to investigate the feasibility of such a scenario, propagation at 55â65 GHz along the arm is measured for two configurations. First, for increasing separation distances along the arm, and second for a transmitter is rotationally placed around the wrist. Two channel gain models are fitted to the data and used to obtain a channel gain exponent in the first configuration and loss per angle of rotation in the second configuration. These models are relevant inputs for the design of future wearable wireless systems

Enabling connectivity for tactical networks in mountainous areas by aerial relays

A general modeling framework for realistic performance evaluations of tactical mobile ad-hoc networks deployed in mountainous areas is presented. The framework is easily extensible, and can be eventually automated. It can be also used to generate data for other network simulators. The framework utilizes the freely downloadable high resolution 3D terrain data to define time dependent trajectories of network nodes. The node speeds and directions are linked to the terrain profile which extends the previously proposed mobility models. The path-loss analysis along the node trajectories revealed the need for aerial relays to enable full network connectivity at all times. The network consisting of 5 cluster heads and a single stationary relay is considered as a case study. The relay location and its antenna height are optimized to achieve the line-of-sight connectivity over the whole mission duration. The antenna radiation pattern at the relay is incorporated in the analysis. The resulting star network topology is used by the cluster heads to broadcast their packets to all other cluster heads. Several relaying schemes including the amplify-and-forward and the decode-and-forward relaying are studied together with the go-back-N retransmissions to achieve the reliable data transfer

The feasibility of using electromagnetic waves in determining membrane failure through concrete

Concrete flat roof defects such as water leakage present a significant and common problem in large buildings, particularly in tropical countries, where rainfall is high. To monitor this condition, effective non-destructive test methods are required to detect problems at an early stage, especially hidden defects within the concrete roof, which are critical. This paper presents the potential use of electromagnetic (EM) waves for determining possible leakage of the concrete flat roof as a result of failure of the waterproof membrane layer. This study was assessed, experimentally by investigation of the propagation of EM waves through the roof and their interaction with water. Novel Microwave sensors described in the paper operate in the 6 GHz to 12 GHz frequency range using a Marconi 6200A microwave test set. A range of existing methods was reviewed and analysed. Results of experimental tests confirmed that microwaves could be used as an alternative non-destructive method for identifying water ingress caused by membrane failure into the concrete roof surface

Studies in RF power communication, SAR, and temperature elevation in wireless implantable neural interfaces

Implantable neural interfaces are designed to provide a high spatial and temporal precision control signal implementing high degree of freedom real-time prosthetic systems. The development of a Radio Frequency (RF) wireless neural interface has the potential to expand the number of applications as well as extend the robustness and longevity compared to wired neural interfaces. However, it is well known that RF signal is absorbed by the body and can result in tissue heating. In this work, numerical studies with analytical validations are performed to provide an assessment of power, heating and specific absorption rate (SAR) associated with the wireless RF transmitting within the human head. The receiving antenna on the neural interface is designed with different geometries and modeled at a range of implanted depths within the brain in order to estimate the maximum receiving power without violating SAR and tissue temperature elevation safety regulations. Based on the size of the designed antenna, sets of frequencies between 1 GHz to 4 GHz have been investigated. As expected the simulations demonstrate that longer receiving antennas (dipole) and lower working frequencies result in greater power availability prior to violating SAR regulations. For a 15 mm dipole antenna operating at 1.24 GHz on the surface of the brain, 730 uW of power could be harvested at the Federal Communications Commission (FCC) SAR violation limit. At approximately 5 cm inside the head, this same antenna would receive 190 uW of power prior to violating SAR regulations. Finally, the 3-D bio-heat simulation results show that for all evaluated antennas and frequency combinations we reach FCC SAR limits well before 1 °C. It is clear that powering neural interfaces via RF is possible, but ultra-low power circuit designs combined with advanced simulation will be required to develop a functional antenna that meets all system requirements. © 2013 Zhao et al

Channel Characteristics of MIMO-WLAN Communications at 60GHz for Various Corridors

[[abstract]]A comparison of 4 × 4 multiple-input multiple-output wireless local area network wireless communication characteristics for six different geometrical shapes is investigated. These six shapes include the straight shape corridor with rectangular cross section, the straight shape corridor with arched cross section, the curved shape corridor with rectangular cross section, the curved shape corridor with arched cross section, the L-shape corridor, and the T-shape corridor. The impulse responses of these corridors are computed by applying shooting and bouncing ray/image (SBR/Image) techniques along with inverse Fourier transform. By using the impulse response of these multipath channels, the mean excess delay, root mean square (RMS) delay spread for these six corridors can be obtained. Numerical results show that the capacity for the rectangular cross section corridors is smaller than those for the arched cross section corridors regardless of the shapes. And the RMS delay spreads for the T-and the L-shape corridors are greater than the other corridors.[[notice]]補正完畢[[incitationindex]]SCI[[incitationindex]]EI[[booktype]]紙本[[booktype]]電子