The lower bounds on Q for lossy electric and magnetic dipole antennas

Best,; Yaghjian,

doi:10.1109/lawp.2004.838822

Cited by 39 publications

(24 citation statements)

References 6 publications

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“…In reality, eddy currents cause the current to bunch around the wire's surface, which increases the loss resistance of both multi-turn and single-turn loops [26]. This makes it difficult to accurately estimate the radiation efficiency of wire antennas using conventional methods [11][12][13].…”

Section: A Capacitively Loaded Te10 Antenna (Magnetic Dipole)mentioning

confidence: 99%

“…To date, the most common method of analytically estimating tradeoffs between radiation efficiency and size is to consider common antenna types (e.g. capacitively loaded loop, inductively loaded dipole), and then approximate the current distribution to calculate the radiated and dissipated power [11][12][13]. However, this approach is not general.…”

Section: Introductionmentioning

confidence: 99%

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Fundamental Efficiency Limits for Small Metallic Antennas

Pfeiffer

2017

IEEE Trans. Antennas Propagat.

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-Both the radiation efficiency and bandwidth of electrically small antennas are dramatically reduced as the size decreases. Fundamental limitations on the bandwidth of small antennas have been thoroughly treated in the past. However, upper bounds on radiation efficiency have not been established even though it is also of significant importance. Here, radiation from a thin metallic shell is rigorously analyzed to establish fundamental limits on the radiation efficiency of resonant, electrically small antennas in terms of the size and the metal conductivity. Metallic losses are systematically introduced into the circuit model proposed by Chu, and several resonant antennas with maximum radiation efficiencies are analyzed. Resonant electric and magnetic dipole antennas both have maximum radiation efficiencies near 100% until the size is reduced below a critical value, at which point the efficiency scales as electrical size to the fourth power ሺሺሻ ሻ. It is also shown that a helix antenna that resonantly couples the TM10 mode to the TE10 mode has a maximum radiation efficiency, and is about twice that of a resonant dipole or loop antenna. The closed form expressions reported here provide valuable insight into the design of small antennas with optimal efficiencies.

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Section: A Capacitively Loaded Te10 Antenna (Magnetic Dipole)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Fundamental Efficiency Limits for Small Metallic Antennas

Pfeiffer

2017

IEEE Trans. Antennas Propagat.

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“…[9] The reasons for the decreased efficiency of the antenna fabricated using direct transfer patterning is the additional substrate loss, and the lower skin depth due to the higher frequency of operation. [22] Although manual fabrication offers improved performance, manually bending wires is a time consuming and potentially expensive process. Silver ink printing achieves comparable Q 's, but significantly lower efficiency than direct transfer patterned devices since the conductivity of the ink is only 30% that of copper.…”

Section: Communicationmentioning

confidence: 99%

Direct Transfer Patterning of Electrically Small Antennas onto Three‐Dimensionally Contoured Substrates

Pfeiffer

Forrest

et al. 2012

Advanced Materials

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“…As for implantable applications, the closer the antenna is to the skin, the less the signal attenuates within the tissue. Therefore, higher frequencies can be used to avoid the limitations on the radiation efficiency η for electrically small antennas (ESA; if the antenna electrical size ka < 0.5, it can be considered electrically small [13]). The most efficient bands would be the ISM 2.45 GHz for a few cm deep implants and 5.8 GHz for the subcutaneous [11].…”

Section: A Operating Frequency Choicementioning

confidence: 99%

“…Typically, to compensate for the antenna detuning, an extended bandwidth BW is preferred. However, it undermines the radiation efficiency, as BW ∝ ka/η [13].…”

Section: B Improving Efficiency Of In-body Antennasmentioning

confidence: 99%

Long-Range Antenna Systems for In-Body Biotelemetry: Design Methodology and Characterization Approach

2017

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Abstract-Long-range in-body biomedical telemetry enables monitoring of physiological parameters while maintaining mobility and freedom of movement. This emerging technology creates new applications in medicine, clinical research, wellness, and defense. Current in-body biotelemetry devices operate within about a meter around a user that limits their applicability. Here we examine the variety of approaches that, combined, can significantly extend the operating range. The radiation efficiency is constrained by attenuation and reflection losses in tissues. First, choosing an optimal operating frequency can minimize the losses. A specific antenna design is then required to decouple the antenna from a body. Two successful antenna design approaches are reviewed: (1) using loop antennas and (2) dielectrically loaded microstrip antennas. On-body matching layers and repeaters can be used to further improve power transmission. Finally, we present the radiation characterization method for in-body antennas in spherical phantoms with a direct illumination technique using an analog fiber optic link.

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The lower bounds on Q for lossy electric and magnetic dipole antennas

Cited by 39 publications

References 6 publications

Fundamental Efficiency Limits for Small Metallic Antennas

Fundamental Efficiency Limits for Small Metallic Antennas

Direct Transfer Patterning of Electrically Small Antennas onto Three‐Dimensionally Contoured Substrates

Long-Range Antenna Systems for In-Body Biotelemetry: Design Methodology and Characterization Approach

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