Abstract
A metaloop antenna (1FD-MetaLPA), made of C-type metaatoms and having a single feed point, F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> ', is created to radiate a left-hand circularly polarized (LHCP) axial beam at a frequency of f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LH-1FD</sub> = 2.55 GHz and a right-hand circularly polarized (RHCP) axial beam at a frequency of f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RH-1FD</sub> = 3.45 GHz. It is revealed that the maximum gains at f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LH-1FD</sub> and f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RH-1FD</sub> are unbalanced. Subsequently, a number of C-type metaatoms are replaced by N-type metaatoms. The replacement generates a balanced gain of 7.1 dBi with an LHCP gain bandwidth of 7.7% and an RHCP gain bandwidth of 8.3%. The radiation efficiency under the balanced gain is 75% at f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LH-1FD</sub> and 29% at f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RH-1FD</sub> . Next, a large metaloop antenna that radiates a conical beam and has a feed point, F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">O</sub> , is concentrically added to the outside of the gain-balanced 1FD-MetaLPA. This antenna system is designated as the MetaLPA-plus. It is found that the MetaLPA-plus radiates an LHCP tilted beam at f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LH-1FD</sub> and an RHCP tilted beam at f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RH-1FD</sub> . The angle of depression (tilt angle) using equal amplitude excitation is θ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> = 20 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> at f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LH-1FD</sub> and θ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> = 15 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> at f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RH-1FD</sub> . These tilted CP radiation beams are rotated around the antenna axis with change in the excitation phases at points F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> ' and F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">O</sub> . During the beam-steering, the gain for an LHCP wave is nearly constant, with a value between 5 dBi and 6.5 dBi. This also holds true for an RHCP wave.
Highlights
A loop antenna, abbreviated as LPAnT, is a resonant antenna and radiates a linearly polarized (LP) wave [1], [2]
It is found that when the loop length is one guided wavelength (1λg), an LPAnT located in the x-y plane forms an axial beam within the ±z hemispheres
This paper presents an antenna system, abbreviated as the MetaLPA-plus, that is an application of the round
Summary
A loop antenna, abbreviated as LPAnT, is a resonant antenna and radiates a linearly polarized (LP) wave [1], [2]. The presented MetaLPA-plus has a lowprofile structure (the antenna height is on the order of λ0/100) and radiates a CP tilted beam that can be rotated (steered) around the antenna axis at two design frequencies.
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