Effects of a surrounding conducting medium on antenna analysis

Moore, R. K.

doi:10.1109/tap.1963.1138043

Cited by 56 publications

(42 citation statements)

References 10 publications

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“…However, even in air, when the antenna is placed near an interfering obstacle or the altitude from the Earth's surface is low, the operation may be severely disturbed (height gain). Power is lost as heat and the effectiveness is reduced when the antenna is near the surface [21,24]. Most of us have observed that the relocation of the device or a slight movement of the radio antenna makes the situation better in most cases.…”

Section: Discussionmentioning

confidence: 99%

“…Even the determination of the origin (central or end) may lead to confusing solutions in the conducting medium, and the modifications in antenna patterns become more pronounced due to a different viewpoint, unlike in air, where the coordinates of the origin in the proximity of an antenna yield the same result. The phase shift and the attenuation due to the contribution from one end of the antenna relative to that from the other end are not significant [21]. Boreholes are most typically waterfilled, and a water layer might influence the impedance and power delivery of an antenna.…”

Section: Discussionmentioning

confidence: 99%

“…In Fig. (3d), the conductive medium around the antenna broadens the pattern (brown curve) and reduces the directivity [21]. Strictly speaking, the broadening effect is not a major problem at the EMRE frequencies.…”

Section: Borehole Antenna Characteristicsmentioning

confidence: 96%

“…Thus, it is not meaningful to estimate the values of antenna parameters (e.g. antenna pattern, gain, directivity) in a dissipative medium, or the distance from the source must be included in the definitions of these parameters [21].…”

Section: Borehole Antenna Characteristicsmentioning

confidence: 99%

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Borehole Antenna Considerations in the EMRE System: Frequency Band 312.5-2500 kHz

Korpisalo¹

2013

TOGEOJ

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Abstract:The ElectroMagnetic Radiofrequency Echoing (EMRE) system is utilized in radiofrequency imaging (RIM) measurements between two deep boreholes. It is based on radiowave attenuation, making it possible to reconstruct the attenuation distribution of the borehole section (tomogram). The main parts of the EMRE system are a continuous wave (CW) transmitter and superheterodyne-type receiver. The insulated dipole antennas are the transducers between the device and environment, or together they form a transmission line. The system is bistatic because the antennas are placed in separate boreholes.When an antenna is situated in a dissipative medium, e.g. in a deep borehole, its performance becomes highly environmentally sensitive. Direct measurements of the feed-point current and radiative characteristics are impossible, and numerical models must therefore be used to investigate the borehole effects. A generalized transmission line model of an insulated antenna is a simple and useful way to examine the antenna-related properties. A drawback is that the borehole water must be excluded from the models due to the high wave number of water. The commercial simulation package FEKO is a numerical modelling package and a powerful tool when constructing more realistic antenna and borehole models. FEKO models and transmission line models (WKG, CHEN) were compared and the results coincided in the frequency band of 312.5-2500 kHz. According to the FEKO studies, the influence of borehole water and the location of the antenna in the borehole, i.e. centric or eccentric, did not appear to have a significant effect. The scattering parameter s 11 , the ratio of forward and returned power, is a useful antenna parameter to estimate the power level that is radiated from the antenna to the surrounding rock. According to the FEKO models, the highest measurement frequency (2500 kHz) of the EMRE system seems to suffer the most under the borehole conditions due to the low values of s 11 (~-2dB). The performance level of the system determines the maximum distances (translumination distance) at which the signals are still detectable. According to the results using a simplified measurement geometry, the EMRE system can operate at distances of <1000 m when the host rock has resistivities of >10 000 Ωm and the lowest frequency of 312.5 kHz is used. At minor distances of 400-600 m, the system operates well at all frequencies.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Borehole Antenna Characteristicsmentioning

confidence: 96%

Section: Borehole Antenna Characteristicsmentioning

confidence: 99%

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Borehole Antenna Considerations in the EMRE System: Frequency Band 312.5-2500 kHz

Korpisalo¹

2013

TOGEOJ

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“…where d (m) is the distance at which |H| is taken or measured, δ (m) is the skin depth, R r (Ω) is the radiation resistance and i i (A) is the input current [94]. 2.…”

Section: Ref Structure/ Achievementsmentioning

confidence: 99%

A Review on Wireless Power Transfer in Free Space and Conducting Lossy Media

Alrawashdeh¹

2017

JJCIT

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State‐space models and stored electromagnetic energy for antennas in dispersive and heterogeneous media

Gustafsson

Ehrenborg

2017

Radio Science

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Accurate and efficient evaluation of the stored energy is essential for Q factors, physical bounds, and antenna current optimization. Here it is shown that the stored energy can be estimated from quadratic forms based on a state‐space representation derived from the electric and magnetic field integral equations. The derived expressions are valid for small antennas embedded in temporally dispersive and inhomogeneous media. The quadratic forms also provide simple single frequency formulas for the corresponding Q factors. Numerical examples comparing the different Q factors are presented for dipole and meander line antennas in conductive, Debye, and Lorentz media for homogeneous and inhomogeneous media. The computed Q factors are also verified with the Q factor obtained from the stored energy in Brune synthesized circuit models.

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Effects of a surrounding conducting medium on antenna analysis

Cited by 56 publications

References 10 publications

Borehole Antenna Considerations in the EMRE System: Frequency Band 312.5-2500 kHz

Borehole Antenna Considerations in the EMRE System: Frequency Band 312.5-2500 kHz

A Review on Wireless Power Transfer in Free Space and Conducting Lossy Media

State‐space models and stored electromagnetic energy for antennas in dispersive and heterogeneous media

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