Limits on the radiation Q of electrically small antennas restricted to oblong bounding regions

Foltz, Heinrich; McLean, James

doi:10.1109/aps.1999.789365

Cited by 29 publications

(24 citation statements)

References 5 publications

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“…He showed that the dipole modes have the lowest Q-factor and that the Q-factor of antennas can be reduced by letting the antenna excite a combination of electric (transverse magnetic TM) and magnetic (transverse electric TE) modes. Mode expansions have dominated the research on physical bounds since Chu's work, see e.g., [18,19,24,25,27,29,48,60,61,77,83,85,88,91,105,110,119] and the historical expose in [115]. The mode expansion approach to physical limitations provides simple analytic formulas for the lower bound on the Q-factor for single modes [18,85].…”

Section: Background and Overviewmentioning

confidence: 99%

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Physical Bounds of Antennas

Gustafsson¹,

Tayli²,

Cismasu³

2016

Handbook of Antenna Technologies

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Design of small antennas is challenging because fundamental physics limits the performance. Physical bounds provide basic restrictions on the antenna performance solely expressed in the available antenna design space. These limits offer antenna designers a-priori information about the feasibility of antenna designs and a figure of merit for different designs. Here, an overview of physical bounds on antennas and the development from circumscribing spheres to arbitrary shaped regions and embedded antennas are presented. The underlying assumptions for the methods based on circuit models, mode expansions, forward scattering, and current optimization are illustrated and their pros and cons are discussed. The physical bounds are compared with numerical data for several antennas.

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Section: Background and Overviewmentioning

confidence: 99%

“…In small antenna theory, matching bandwidth and the efficiency are two performance parameters often considered for analysis, e.g., [14,18,24,25,27,29,48,60,61,77,85,88,91,105,110,116,119]. The radiation pattern and the polarization are also of importance in some studies [40,43,44].…”

Section: Introductionmentioning

confidence: 99%

Physical Bounds of Antennas

Gustafsson¹,

Tayli²,

Cismasu³

2016

Handbook of Antenna Technologies

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“…Mode expansions have dominated the research on physical bounds since these expansions were introduced by Chu, see e.g., [18,24,25,27,48,61,77,85,88,91,105,110,119] and the historical expose in [115]. In particular Collin & Rothschild [18] used spherical mode expansions and analytic evaluation of (3.8) to derive closed form expressions of the Q-factor for spherical modes of arbitrary order, e.g.,…”

Section: Circuit Models and Mode Expansionsmentioning

confidence: 99%

“…Physical bounds on antennas are often derived using the electromagnetic fields that surround the antenna [18,24,25,27,61,77,85,105,110,115,119]. Consider an antenna confined to the region Ω as depicted in Fig.…”

Section: Stored Electric and Magnetic Energiesmentioning

confidence: 99%

“…This has encouraged researchers to extend the mode expansions to non-spherical regions. Collin and Rothschild [18] used cylindrical waves to derive bounds for infinite cylinders and Foltz & McLean [25] and Sten, Koivisto, and Hujanen [105] used expansions in spheroidal coordinates to derive bounds for antennas confined to spheroidal volumes. However, it turns out to be difficult to extend the results from spherical regions using mode expansions.…”

Section: Circuit Models and Mode Expansionsmentioning

confidence: 99%

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Physical Bounds of Antennas

Gustafsson¹,

Tayli²,

Cismasu³

2015

Handbook of Antenna Technologies

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Conformal Printing of Electrically Small Antennas on Three‐Dimensional Surfaces

et al. 2011

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Increasingly stringent design constraints imposed by compact wireless devices for telecommunications, defense, and aerospace systems require the miniaturization of antennas. Unlike most electronic components, which benefi t from decreased size, antennas suffer limitations in gain, effi ciency, system range, and bandwidth when their size is reduced below a quarter-wavelength. The electrical size of the antenna is measured by its ka value, where k is the wavenumber ( k = 2 π / λ , λ = wavelength at the operating frequency) and a is the radius of the smallest sphere that circumscribes the antenna. Antennas are considered to be electrically small when ka ≤ 0.5. Recent attention has been directed towards producing radiofrequency identifi cation (RFID) antennas by screen-printing, [ 1 ] inkjet printing, [ 2 ] and liquid metalfi lled microfl uidics [3][4][5] in simple motifs, such as dipoles and loops. However, these fabrication techniques are limited in both spatial resolution and dimensionality; yielding planar antennas that occupy a large area relative to the achieved performance.Omnidirectional printing of metallic nanoparticle inks offers an attractive alternative for meeting the demanding form factors of 3D electrically small antennas (ESAs). We have previously demonstrated that fl exible, stretchable, and spanning silver microelectrodes with features as small as ∼ 2 μ m can be patterned both in and out-of-plane (e.g., spanning arches) on fl at substrates by this approach. [ 6 ] Here, for the fi rst time, we demonstrate the conformal printing of silver nanoparticle inks on curvilinear surfaces to create electrically conductive meander lines. When interconnected with a feed line and ground plane, the resulting 3D ESAs exhibit performance properties that nearly match those predicted theoretically for these optimized designs.Antennas act as effective transducers between free space and guided waves over a range of frequencies, known as their impedance bandwidth. The impedance of most small antennas can be approximated by a single resistor-inductor-capacitor (RLC) circuit, and their bandwidth is inversely proportional to their radiation quality factor ( Q ), defi ned as the ratio of energy stored to energy radiated. [ 7 ] Because of this inverse relationship, a low Q serves to increase bandwidth, and therefore the data rate over a given wireless channel. However, a fundamental relation exists between the antenna size and Q . [ 8 , 9 ] As the maximum dimension decreases below a wavelength, the bound on the minimum attainable Q rapidly increases, a phenomenon commonly referred to as Chu's limit -an important fi gure of merit for antenna performance. While Thal recently derived a more accurate bounding limit, [ 10 ] both limits depend on the electrical size of the antenna. For decades, researchers have sought antenna designs that approach these fundamental lower limits. However, prior efforts, such as those based on genetic algorithms [ 11 , 12 ] lack fl exibility, since their output cannot be modifi ed in a straightfor...

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Limits on the radiation Q of electrically small antennas restricted to oblong bounding regions

Cited by 29 publications

References 5 publications

Physical Bounds of Antennas

Physical Bounds of Antennas

Physical Bounds of Antennas

Conformal Printing of Electrically Small Antennas on Three‐Dimensional Surfaces

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