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A broadband circularly polarized microstrip antenna using an artificial ground (AG) structure is presented. In this paper, the effect of the ground plane is discussed on the bandwidth of S11 and axial ratio (AR).
High impedance surfaces (HIS) as substrates are studied as an efficient way of designing low profile antennas. HIS of printed dogbone elements on a grounded substrate was previously used for improving the radiation performance of a printed folded dipole on top of it. Furthermore, it was demonstrated that the HIS comprising dogbones can also be used as an antenna itself, thanks to the leaky waves it...
Position and orientation measurements have been demonstrated, recently, using low-frequency magnetoquasistatic fields and complex image theory for distances up to 50 m [1]. The key motivation for using magnetoquasistatic fields is to enable accurate estimation of an object's position and orientation when near weakly conducting dielectric obstacles, e.g., groups of people. An example application is...
In this paper, a metasurface structure is designed specifically for a 60 GHz on-chip antenna implementation. The design concept, characteristics and fabrication are discussed and the simulation results are well compared with the measurement. Then, the advantage of using metasurface integrated with both active loads and Varactors to enhance the tunability is explored.
We present an analytical model to study the reflection properties of a multilayered wire media loaded with 2-D arrays of thin imperfect conductors. Based on charge conservation, generalized additional boundary conditions (ABCs) for the interface of two uniaxial wire mediums loaded with thin arbitrary imperfect conductors at the junction are derived. It is observed that by proper selection of the structural...
We measured and characterized the radar response of twenty-five vehicles to evaluate the quality of surrogate test targets. The vehicles are selected form a broad range of vehicle classes and include several that are frequently struck in rear-end collisions as determined by the U.S. National Crash Database [1]. Each vehicle's response is measured with a wideband, millimeter wave, instrumentation radar...
A multiband metamaterial operating in the 0 THz to 2 THz range was designed with two high refractive index values. The dimension of the slab of the metamaterial is 300 um by 300um and the thickness is 17.45 um. Twenty five resonant metallic structures were placed in the substrate material, with a gap of 1.2 um between each unit. Results show enhanced dielectric response as well as suppressed diamagnetic...
We analyze the effects of mutual coupling and spatial correlation on the performance of multi-user MIMO systems having a large number of antenna elements at the base station (‘large-scale’ MIMO or ‘massive’ MIMO). We show that these effects set a practical limit on the maximum number of antennas that can be packed into any given physical base station size, above which no further spectral efficiency...
In this contribution, a new algorithm derived based on a two-layer evidence framework is applied to estimating parameters in the generic stochastic channel models from measurement data. Different from conventional high-resolution parameter estimation algorithms, e.g. the space-alternating generalized expectation-maximization (SAGE), the method proposed is applicable to extracting both the parameters...
Metamaterials have been previously studied for their ability to tailor the dispersive IR emissivity of a surface. Here, we investigate a metamaterial structure based on an electromagnetic band-gap surface for use as near-IR emitters with custom polarization selectivity. A genetic algorithm is successfully employed to optimize a metamaterial structure to exhibit maximum circularly polarized emissivity...
In this work the beam-scanning capability of a gradient index fishnet array, which is designed to operate at 22.5 GHz, is investigated. The results are discussed based on unit cell simulations and far-field measurements. The gradient is realized by changing the permittivity of a dielectric layer in each unit cell element resulting a tuning of the magnetic resonance frequency. Hence, an effective differential...
This paper discusses the approach to make use of the four towers in the existing Sectionalized Loran Transmitting (SLT) antennas. Various configurations have been investigated to operate at lower frequency with reasonable behavior. Upward radiation is desired so horizontal polarization is used. A High Impedance Surface (HIS) is introduced between the antenna and the ground plane to improve performance...
A laboratory-fabrication of embroidered antennas for ultra high frequency (UHF) radio frequency identification (RFID) tags is presented. The embroidered antenna patterns are formed from conductive thread using software controlled embroidery machine. Measurements of fully assembled embroidered UHF RFID tag verify that competitive tag performance can be achieved with the presented fabrication method.
Study of ground wave propagation in the high frequency range is presented. It is shown that the received electric field increases with the transmitting antenna height h, when h exceeds a certain critical height that is a function of the earth's conductivity and the applied wavelength. Numerical results are given for poorly conducting, well conducting and highly conduction earth.
This paper presents the results of an investigation into a compact circularly polarized (CP) antenna for operation at 400MHz. The antenna consists of an array of four folded shorted patch (S-P) elements constructed using multilayer printed circuit board (PCB) technology. The overall dimensions of the antenna are 0.2λ0 X 0.2λ0 X 0.05λ0. The design may be applicable for CP antenna systems on micro-satellites...
In this paper, the characteristics and possible applications of a new antenna substrate material which is developed using paraffin wax is discussed. The substrate is a low loss material and helps to achieve high performance antennas for various applications. This type of low cost substrate material can be molded into different shapes and forms. They can be used as antenna substrate materials in various...
A novel spiral antenna with miniature configuration is proposed by introducing lumped resistive loading along the spiral arms. A transmission-line model incorporating the loss resistance is introduced to help study the method. Numerical simulation examples have been demonstrated that antenna size could be reduced significantly while maintaining the axial ratio characteristics. A partly loading structure...
This paper presents a novel method for determining the power available to a passive radio-frequency identification (RFID) tag, the Power Conversion Gain (PCG). The power conversion gain of a tag combines the tag's antenna pattern with its charge pump efficiency to give the system designer the tag's output power as a function of angle and maximum received input power. This metric is more useful for...
Magneto-dielectric material is developed for the design of electrically small monopole antenna at the VHF band. It has very promising property of permeability and permittivity to realize antenna height reduction factor of less than 1/4. The designed electrically small magneto-dielectric coated VHF monopole antenna, with its height of 250 mm, can operate at 71.14 MHz with good matching to 50Ω SMA connector.
Effect of loading a simple monopole antenna with magneto-dielectric material is investigated. The advantages in loading the antenna with magneto-dielectric material over loading with either dielectric or magnetic material for antenna miniaturization applications is demonstrated. To better compare the effects of different material loading, the shift in resonant frequency and the corresponding change...
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