In this paper, a simple-fed, low profile, 9×10 elements quasi-lumped planar antenna array is presented. The proposed resonator employs a quasi-lumped element resonator that uses interdigital capacitor (IDC) in parallel with a straight strip inductor shorted across the capacitor. The array elements were designed and then excited by a feed network of four coaxial probes situated at the bottom plane but separated from the ground plane using a plastic material. The entire array is divided into four sub-array lattices of 5×5 elements and excited by a coaxial probe located at the centre of the sub-arrays antenna structure, thus exciting the centre resonator who in turn excites the neighbouring elements via proximity coupling. The probes are connected based on Wilkinson power divider principle to provide in-phase excitation. An explicit method is introduced to quickly obtain the array factor (AF) characteristics for such proximity coupled rectangular planar array. Radiation pattern and the array factor are presented, and are further compared with those obtained by the simulation and experimental results. The proposed antenna comprises 9×10 elements array, each of which is 5.8×5.6 sq. mm in size, and the entire antenna structure is about 120×80 sq. mm.
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