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(LOW) (wavelength lambda(LOW)) and at high frequency f(HIGH) (wavelength lambda(HIGH)); 2) a small antenna volume of less than 0.01 lambda(3)(LOW); 3) a small antenna height on the order of lambda(LOW)/100; 4) a small conducting antenna footprint of 0.62 lambda(LOW) x 0.49 lambda(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(LOW) using an equal-amplitude/inphase excitation mode. This is also shown to be true at f(HIGH). Thirdly, each of the obtained CP broadside beams at f(LOW) and f(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 degrees to theta = +30 degrees at f(LOW) and theta = -40 degrees to theta = +25 degrees at f(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(LOW) and 1.4 dB at f(HIGH).