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

A circularly polarized (CP), small, beam-steerable antenna is realized using bent metalines. The antenna has the following features: 1) dual-band operation at low frequency
$f_{\mathrm {LOW}}$
(wavelength
$\lambda _{\mathrm {LOW}}$
) and at high frequency
$f_{\mathrm {HIGH}}$
(wavelength
$\lambda _{\mathrm {HIGH}}$
); 2) a small antenna volume of less than
$0.01\lambda _{\mathrm {LOW}}^{3}$
; 3) a small antenna height on the order of
$\lambda _{\mathrm {LOW}}$
/100; 4) a small conducting antenna footprint of
$0.62\lambda _{\mathrm {LOW}}\times 0.49\lambda _{\mathrm {LOW}}$
; and 5) a phased array antenna consisting of minimum array elements (two elements). Firstly, the antenna characteristics of straight and bent metalines are briefly summarized. Secondly, it is shown that an array antenna composed of two bent metalines forms a CP broadside beam at
$f_{\mathrm {LOW}}$
using an equal-amplitude/in-phase excitation mode. This is also shown to be true at
$f_{\mathrm {HIGH}}$
. Thirdly, each of the obtained CP broadside beams at
$f_{\mathrm {LOW}}$
and
$f_{\mathrm {HIGH}}$
is steered within the H-plane. The array antenna is found to have a CP beam that is steerable across a region of
$\theta = - 40^{\circ }$
to
$\theta = + 30^{\circ }$
at
$f_{\mathrm {LOW}}$
and
$\theta = - 40^{\circ }$
to
$\theta = + 25^{\circ }$
at
$f_{\mathrm {HIGH}}$
, with an axial ratio of less than 3 dB. During the beam steering, the gain deviation from its maximum value is found to be small: 1.7 dB at
$f_{\mathrm {LOW}}$
and 1.4 dB at
$f_{\mathrm {HIGH}}$
.