Flexible, Conformal, Endfire Radiating, Electrically Small Antennas on a Conducting Cylinder With a Small Radius

A design of a flexible, uniplanar, vertically polarized, Yagi-configured, electrically small antenna (ESA) that can be conformally mounted on a conducting cylinder with a small radius for endfire radiation is presented. To create a Yagi-configured antenna with both an electrically small size and uniplanar configuration, an interdigital structure is utilized to divide the top-hat of the driven monopole into two parts, and a C-shaped slot is etched at the top-hat of the reflecting monopole to significantly lower its resonant frequency. The ESA's stable radiation performance characteristics were maintained when it was mounted on small conducting cylinders with different radii. A 6-element array prototype that entirely encircles a conducting cylinder with only a 50 mm radius was fabricated and measured. The measured results, which are in good agreement with their simulated values, demonstrate that, with a low profile (0.035λ_L) and electrically small size (ka = 0.82), the proposed vertically polarized antenna can operate in a frequency range centered at 1.7 GHz, and exhibits an 8.2% impedance bandwidth and a 6.4 dBi peak realized gain. Because it has the advantages of electrically small size and flexibility to conform to the conducting cylinder with small radius, it should be very attractive for many miniaturized aircraft in the future.