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Showing 1 to 20 of 21 for “"electrically small antennas"”.
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Design and Analysis of Circularly Polarized Electrically Small Antennas
… applications, circular polarization in antennas is needed for efficient communication. In this thesis, the miniaturization technique known as T-top loading is utilized on two novel antenna designs. One design is an electrically small, circularly polarized planar cross dipole and the …
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Characteristic Modes for Impedance Matching and Broadbanding of Electrically Small Antennas
Antennas smaller than a quarter wavelength are fundamentally constrained in a variety of ways. One of the more problematic limitations is that the antenna's bandwidth declines sharply as the size of the antenna decreases. Myriad studies have sought antennas that perform close to the fundamental …
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Investigation of electrically small antennas designed for directive radiation from transient signaling
Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2027-05-01
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Design and analysis of direction-of-arrival estimation systems using electrically small antenna arrays
… whose interelement phase di erence is very small or even negligible. Traditionally, direction- nding systems have been quite large to ensure a re- solvable phase delay between elements. Since the direction- nding arrays presented here are much less reliant on interelement phase delay, their …
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The utilisation of commercial off the shelf carbon nanotube fibre in individual metamaterial antennas to enable a reduction in operating frequencies
… of metamaterial research, can be used to produce electrically small antennasWe find that basic improvements to metamaterial antenna designs enable low broadcast frequencies utilising standard bulk metals. However, the increased surface area of the carbon nanotube fibre enables further reductions …
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Time-Variant Components to Improve Bandwidth and Noise Performance of Antennas
… Thus, the design of low-noise devices (such as antennas, amplifiers, and filters) is essential to increase the communication range. Also, it is well known that the noise performance of a receiving radio is primarily determined by the frontend including the antenna, filter, and a low-noise …
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Investigation of Low Profile Antenna Designs for Use in Hand-Held Radios
Antennas in hand-held radios must be compact and unobtrusive. Electrically small and low-profile antennas experience high input reactance, low input resistance, and low radiation efficiency.Further degradation of radiation efficiency occurs in hand-held radios due to size-reduced ground planes, …
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Synthesis Imaging with Vector Sensor Arrays
… in conducting these observations. Parabolic antennas, which are commonly used for radio astronomy, would need to be impractically large to obtain high angular resolution at frequencies below roughly 100 MHz. Instead, to observe frequencies between 10 MHz and 100 MHz, observatories use …
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A Nonlinear Technique for Bandwidth Improvement in Narrowband Antennas
Electrically small, low profile antennas have become the new frontier in wireless communication research. With the pressure to miniaturize wireless communication devices, engineers are turning to small low profile antennas as a way to reduce their antennas and hence their devices. Ideally, one …
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Precision hot-melt freeform 3D printing for monolithic multilayer microfluidics
… The problem of fabricating networks of small tubes in diverse media is ubiquitous, yet there is still no “black box” that laboratories can buy to turn microfluidic designs into microfluidic chips. 3D printing predates soft lithography, yet only recently have 3D printing methods been …
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A Prototype Platform for Array Feed Development
… spatial filtering by placing an array of electrically small antennas at the focal plane of a parabolic reflector. This thesis documents the design and characterization of a prototype array feed and RF receiver that were used to demonstrate the spatial filtering principle. The array …
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Time-varying Small Antennas for Wideband Applications
… to achieve a high-rate data transmission through electrically small antennas. However, the overall transmission bandwidth is limited by the antenna size. As a well-known physical limitation, maximum achievable bandwidth of a small antenna is governed by the fundamental limit which defines a lower …
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An analysis of the bandwidth oscillations caused by finite ground planes using characteristic mode theory
… the impedance bandwidth for planar inverted-F antennas (PIFAs) changes as the rectangular ground plane changes length. Although previous research has characterized these changes, it has failed to adequately explain why the bandwidth and pattern changes occur. This thesis explains why these …
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Novel Metamaterial Blueprints and Elements for Electromagnetic Applications
… the radiation from horizontal wire and patch antennas in the presence of such substrates. Fundamental characteristics such as return loss and radiation pattern of the antennas are investigated in detail. Finally, transformation optics is also applied to design cylindrical impedance-matched …
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Electrically-Small Antenna Performance Enhancement for Near-Field Detuning Environments
… enhancement of low-profile omnidirectional, electrically-small antennas has evolved from the design and construction of AM transmitter towers eighty years ago to current market demand for battery-powered personal communication devices. Electrically-small antenna theory developed with …
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An investigation of series LC resonant circuits within a sleeve balun to achieve wideband operation
In antenna measurements, it is not recommended to connect a balanced antenna directly to the coaxial cable feed. A balun is required to prevent surface current from flowing onto the outer shield of the feed cable. Balun chokes like the sleeve balun, also known as bazooka balun or quarter-wavelength …
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Electromagnetic Exposure In A Phantom In the Near and Far Fields of Wire and Planar Antennas
… (EM) exposure from wireless devices and antennas. The metric that quantifies the exposure level is called the Specific Absorption Rate (SAR). Wireless devices must satisfy the regulatory standards before being marketed. In the past, researchers have primarily focused on investigating the …
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Wideband Low-Profile Antenna Arrays: Fundamental Limits and Practical Implementations
… a growing need for high performance, compact antennas. Low-profile wideband phased arrays are of particular interest, and have recently been shown to be capable of extremely large bandwidths. However, the size, weight, and cost of phased arrays still makes them impractical for many …
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Wave Engineering in Time Modulated, Nonlinear, and Anisotropic Metamaterials
… Specifically, at RF I will show that small periodic temporal modulation of nonlinear matching network can enhance the radiation of electrically small antennas by boosting unbalanced energy exchange between the wave and the modulating pump. I will show how large modulation ratios can be …
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Analysis and design of compact low profile antennas for fixed volume applications
Item withdrawn by Mark Zulauf (zulauf@illinois.edu) on 2013-01-10T20:26:15Z Item was in collections: University of Illinois Theses & Dissertations (ID: 1) No. of bitstreams: 1 VanNiekerk_Carlo.pdf: 26003010 bytes, checksum: 915d921e86907a553b17985392559c1a (MD5)
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