Compound Metaloop Antenna for Circularly Polarized Beam Steering

Abstract

A metaloop antenna (1FD-MetaLPA), made of C-type metaatoms and having a single feed point, F L ', is created to radiate a left-hand circularly polarized (LHCP) axial beam at a frequency of f LH-1FD = 2.55 GHz and a right-hand circularly polarized (RHCP) axial beam at a frequency of f RH-1FD = 3.45 GHz. It is revealed that the maximum gains at f LH-1FD and f RH-1FD 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 LH-1FD and 29% at f RH-1FD . Next, a large metaloop antenna that radiates a conical beam and has a feed point, F O , 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 LH-1FD and an RHCP tilted beam at f RH-1FD . The angle of depression (tilt angle) using equal amplitude excitation is  max = 20 o at f LH-1FD and  max = 15 o at f RH-1FD . These tilted CP radiation beams are rotated around the antenna axis with change in the excitation phases at points F L ' and F O . During the beamsteering, 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. INDEX TERMSCircularly polarized wave, Dual band operation, Loop antenna, Metaatoms, Steerable beam.

Isolated Gain Enhancement for Dual-Band C-Metaloop Antennas Using a Coplanar Compound Method

“…In contrast, increasing the small gain for the C-RoMLA at f N in [18] is performed without using a parasitic element above the loop; this is done by increasing the antenna arm length. However, the increase in the arm length causes complex antenna design and high fabrication cost; in addition, another gain at fH changes with additional arm length.…”

“…Note that IsoGE provides more freedom than the non-IsoGE in the design of CP communication systems. Table I summarizes the gain enhancement (relative to the initial gain) of the prior CP metamaterial antennas [16], [18], [19], [20], [21], where G LH and G RH denote the LHCP and RHCP gains, respectively. The antenna structure using C-type meta-atoms [16], [18], [19], [21] acts as a dual-band antenna, and the antenna structure using quasi-N-type meta-atoms [20] also acts as a dual-band antenna.…”

“…Table I summarizes the gain enhancement (relative to the initial gain) of the prior CP metamaterial antennas [16], [18], [19], [20], [21], where G LH and G RH denote the LHCP and RHCP gains, respectively. The antenna structure using C-type meta-atoms [16], [18], [19], [21] acts as a dual-band antenna, and the antenna structure using quasi-N-type meta-atoms [20] also acts as a dual-band antenna. On the other hand, the antenna structure using N-type meta-atoms [19] acts as a single-band antenna.…”

A Small Metaline Array Antenna for Circularly Polarized Dual-Band Beam-Steering

“…Also, we recall that these tilted CP beams are designed for single frequency band operation. With the advancement of modern communication systems, antennas whose CP beam direction is electrically controlled have been receiving attention as beam-steerable antennas [20]- [26]. In addition, modern communication systems have been accelerating development of dual-frequency CP operation antennas from the viewpoint of increasing communication capability [20].…”

Theoretical Consideration of Axial Ratio Deterioration in CP Loop-Shaped Antennas

“…[9][11][13]. C2: As the arm width, w, for the loop antennas in Figs.1(a) and (b) becomes wider, the attenuation constant, , increases.…”