Topic

# Loop antenna

About: Loop antenna is a research topic. Over the lifetime, 14808 publications have been published within this topic receiving 185972 citations.

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01 Dec 1947

TL;DR: In this paper, a simple formula for the more fundamental properties of small antennas and their behavior in a simple circuit is given for 1-Mc operation in typical circuits, which indicates a loss of about 35 db for the I.R.E. standard capacitive antenna, 43 db for a large loop occupying a volume of 1 meter square by 0.5 meter axial length, and 64 db for an antenna loop of 1/5 these dimensions.

Abstract: A capacitor or inductor operating as a small antenna is theoretically capable of intercepting a certain amount of power, independent of its size, on the assumption of tuning without circuit loss. The practical efficiency relative to this ideal is limited by the "radiation power factor" of the antenna as compared with the power factor and bandwidth of the antenna tuning. The radiation power factor of either kind of antenna is somewhat greater than (1/6π) (Ab/l2) in which Ab is the cylindrical volume occupied by the antenna, and l is the radianlength (defined as 1/2π wavelength) at the operating frequency. The efficiency is further limited by the closeness of coupling of the antenna with its tuner. Other simple formulas are given for the more fundamental properties of small antennas and their behavior in a simple circuit. Examples for 1-Mc. operation in typical circuits indicate a loss of about 35 db for the I.R.E. standard capacitive antenna, 43 db for a large loop occupying a volume of 1 meter square by 0.5 meter axial length, and 64 db for a loop of 1/5 these dimensions.

1,249 citations

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TL;DR: In this paper, an exact method for the calculation of the minimum radiation Q of a general antenna was derived, which is more straightforward than those previously published, and has implications on both the bandwidth and efficiency of antennas which fall into this category.

Abstract: An exact method, which is more straightforward than those previously published, is derived for the calculation of the minimum radiation Q of a general antenna. This expression agrees with the previously published and widely cited approximate expression in the extreme lower limit of electrical size. However, for the upper end of the range of electrical size which is considered electrically small, the exact expression given here is significantly different from the approximate expression. This result has implications on both the bandwidth and efficiency limitations of antennas which fall into this category.

978 citations

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TL;DR: In this article, the multiband behavior of the fractal Sierpinski (1915) antenna is described and compared to the well-known single-band bow-tie antenna.

Abstract: The multiband behavior of the fractal Sierpinski (1915) antenna is described. Due to its mainly triangular shape, the antenna is compared to the well-known single-band bow-tie antenna. Both experimental and numerical results show that the self-similarity properties of the fractal shape are translated into its electromagnetic behavior. A deeper physical insight on such a behavior is achieved by means of the computed current densities over the antenna surface, which also display some similarity properties through the bands.

754 citations

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01 Aug 1959

TL;DR: In this paper, the radiansphere is defined as the boundary between the near field and the far field of a small antenna, and the power that can be intercepted by a hypothetical isotropic antenna is that which flows through the radianphere or its cross section, the "radiancircle."

Abstract: The "radiansphere" is the boundary between the near field and the far field of a small antenna. Its radius is one radianlength (?/2?), at which distance the three terms of the field are equal in magnitude. A "small" antenna is one somewhat smaller than the radiansphere, but it has a "sphere of influence" occupying the radiansphere. The power that theoretically can be intercepted by a hypothetical isotropic antenna is that which flows through the radiansphere or its cross section, the "radiancircle." From a small electric dipole, the far field of radiation is identified as a retarded magnetic field. Between two such dipoles, the far mutual impedance is that of mutual inductance, expressed in terms of space properties and the radiansphere. A small coil wound on a perfect spherical magnetic core is conceived as an ideal small antenna. Its radiation power factor is equal to the ratio of its volume over that of the radiansphere. A fraction of this ratio is obtainable in various forms of small antennas (C or L) occupying a comparable amount of space. A radiation shield, in the form of a conducting shell the size of the radiansphere, enables separate measurement of radiation resistance and loss resistance.

593 citations

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15 Jan 2007

TL;DR: An antenna for a communications device having configurable elements controlled to modify an antenna impedance and/or an antenna resonant frequency to improve performance of the communications device is described in this article, where the antenna impedance is controlled to substantially match to an output impedance of a power amplifier that supplies the antenna with a signal for transmission.

Abstract: An antenna for a communications device having configurable elements controlled to modify an antenna impedance and/or an antenna resonant frequency to improve performance of the communications device The antenna impedance is controlled to substantially match to an output impedance of a power amplifier that supplies the antenna with a signal for transmission The antenna resonant frequency is controlled to overcome the effects of various operating conditions that can detune the antenna or in response to an operable frequency band

574 citations