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A metafilm consisting of a planar periodic array of electrically small dielectric spheres that are electrically small in spacing is known to support guided waves in certain frequency ranges. In this paper, we examine the effect of slight radius variations between spheres in the array. Such variations may be due to process effects during fabrication, or may be introduced intentionally in order to obtain...
Surface currents due to high power microwaves can damage or interfere with sensitive antennas and electronic devices. Absorbers tend to be thick and heavy, and reactive coatings such as high impedance surfaces alter the scattering properties of a surface, thereby affecting the radiation pattern of nearly antennas. In this paper, a novel metamaterial surface with nonlinear properties is introduced,...
This work presents an extension of Transformation Optics (TO) to control the wavefront of surface waves (SW) through the use of modulated metasurfaces. As the outputs of the conventional TO approach are the metamaterial constitutive parameters able to perform a certain modification of the ray-field path, here the outcomes are the components of the metasurface reactance tensor. This methodology can...
This paper presents two electronically steered phased array approaches allowing to reduce the number of phase shifter bits required to control steering and polarization. The first approach is based on particular combination of the phase shifters arrangement and elements rotation, while the second introduces a different approach with a combination of simplified phasing approach and aperiodic lattice...
A Ku-band wide angle variable linear polarization rotator with high cross-polarization discrimination (XPD) was designed, fabricated and measured. The rotator makes use of two 90° meanderline polarizers and a linear grid to perform the polarization rotation and cross-polarization suppression. The advantage of the present arrangement is that it requires only one rotating mechanism rather than the multiple...
In Kyoto University, we study microwave power transmission (MPT) and solar power satellite (SPS) MPT system. We have an advanced phased array system to make experiments on beam forming with phased array. The advanced phased array system has 256 antenna elements and 5-bit digital phase shifters. We measured and simulated the radiation patterns of the advanced phased array system and compared the measurement...
In this paper a flush-mounted circumferential microstrip array, designed as a sounding rocket telemetry antenna, is reported. The purpose is to comply with the requirements of an international competition for engineering students. Experimental results validate the design approach.
Over the past decade, Earth observing missions which employ spaceborne combined radar & radiometric instruments have been developed and implemented. These instruments include the use of large and complex deployable antennas whose radiation characteristics need to be accurately determined over 4p steradians. Given the size and complexity of these antennas, the performance of the flight units cannot...
Numerically rigorous full-wave electromagnetic analysis of scattering from hailstones based primarily on the method of moments is presented. The analysis employs generalized curved hexahedral volume and surface elements of arbitrary geometrical-mapping orders, current polynomial vector basis functions of arbitrarily high expansion orders, and higher order modeling of inhomogeneous lossy dielectric...
Non-Foster impedance matching circuits for electrically small dipoles and monopoles generally require floating series negative capacitors. A new circuit for this purpose is proposed. The circuit is based on a restricted class of components that admits only positive and negative resistors, capacitors, and gyrators. In particular, no negative capacitors or inductors are needed. Non-Foster 2-port circuits...
This paper investigates the limitation of Negative Impedance Converter (NIC) using Operational Amplifier (Op-Amp). The limitation is theoretical analyzed and then experimentally verified. The results show that, the Op-Amp based NIC has complex input impedance. In addition, the input impedance presents a negative resistance with large magnitude, if a negative small capacitance is desired for matching...
In this paper, an analytic model for the mixed path mode of ionospheric clutter associated with high frequency surface wave radars (HFSWR) operating in an ocean environment is presented. Based on earlier work, an expression for the first-order received electric field after a single scatter from each of the ionosphere and sea surface is derived and reduced to integral form. The integrals are taken...
High efficiency microstrip patch antenna elements developed in the framework of a green radio technology European Union research project are presented. Wide band aperture-coupled stacked-patch configurations with foam substrates are used. The cheap and low losses low dielectric constant foam substrate used leads to a high efficiency and wide bandwidth printed antenna solution. The good agreement between...
This paper presents an experimental comparison between two very different frequency bands: 2–10 GHz and 57–66 GHz. A line of sight indoor environment has been selected, and both bands have been measured under the same conditions and equipment; path loss, delay spread and statistical distributions have been properly compared.
An experimental setup is designed to study transmit beamforming over UWB multiple antenna configurations. We use time-domain spread spectrum channel sounding to simultaneously characterize system impulse responses and prove our capability to carry out high accuracy measurements. By exploiting the high quality impulse response data, we applied multiple input single output (MISO) phase compensation...
This contribution deals with the detection of programme making and special event applications by spectrum sensing. In particular the effect of site specific positioning of spectrum sensors is discussed and is of interest especially to cognitive systems. The procedure of energy detection of the devices is based on a stochastic fading channel performed by ray tracing analysis within an exhibition hall...
Breakdown phenomena were studied when high power microwave pulses radiated to the atmosphere through the split horn antenna. The electrical characteristics of radiated signal such as power and pulse width strongly influence on the breakdown phenomena. This paper provides the information about threshold limitations of the antenna to radiate without breakdown phenomena.
A prediction tool for the transmitted and received power of cellular devices in indoor femtocell environments is presented. Measurements in an office building are performed and compared with the predicted values. An excellent correspondence is obtained, with maximal errors around 3 dB. This research allows predicting exposure doses in indoor femtocell scenarios.
Channel capacity in wireless communications is affected by the signal loss between a pair a transmitter and receiver and is studied here for the simple case of a two-ray model over a lossy half space. This is a classic Sommerfeld problem and has recently been extensively studied by Sarkar et. al. Approximate models often provide rapid solutions but their limitations are as such unknown. In this investigation...
A new method for indoor localization at 60 GHz is proposed. This method is based on the extraction of the TDOA (Time Difference of Arrival), using a MISO system. With this method, unlike conventional TDOA measurements, it is possible to perform communication and localization at the same time by transmitting two identical UWB OFDM signals using two antennas at the TX and extracting TDOA from the interference...
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