Radiation properties of wireless-sensor-targeted compact arrays loaded by ground defects

Printed monopoles are suitable radiators for sensor nodes, and straightforward enablers of compact arrays. Arrays offer the advantage of diversity, which is a true enabler of mobile sensor networks. However, compact arrays with closely spaced elements become detuned and lose bandwidth, while mutual coupling hinders diversity. Prior studies described a simple and efficient technique to reduce coupling and regain the bandwidth by inserting a defect on the ground plane of the device; multi-decibel coupling reduction was noted. This work describes the improvement in radiation efficiency and the minimal distortion of the far-field pattern caused by the insertion of the defect. Array performance was studied numerically in terms of broadband total efficiency and far-field pattern.