Low-Profile Conical Beam Array Antenna Based on Concentric Annular Planar Inverted-F Antenna Elements

Abstract

A planar conical beam array antenna with low profile, high gain, and low side lobe level (SLL) is proposed in this letter. The array is composed of three concentric annular planar inverted-F antenna (APIFA) elements, each of which is excited by uniform distributed feeding points with the same excitation amplitude and phase and thus obtain an axisymmetric conical beam. Shorting pins and cambered slots are employed on the APIFA element to realize impedance matching for a given number of feeding points. Synthesis of conical beam for the array can be flexibly realized by adjusting the excitation amplitudes and phases of the elements. A prototype with a low profile of 0.11 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is designed, fabricated, and measured. Measured results show that the prototype achieves 11.2% (4.71 ∼ 5.27 GHz) -10-dB impedance bandwidth. Within the impedance bandwidth, a stable gain of 11.3 to 12.7 dBi, a stable beam-pointing angle (BPA) of about 15°, and a low SLL of less than -12.5dB is obtained, indicating good conical beam performance.