High‐gain printed monopole arrays with low‐complexity corporate‐feed network

Printed monopole antennas fed by microstrip lines can provide a wide bandwidth and can be employed as terminal antennas in RF circuits. In the same perspective, the authors propose a novel planar array in which N + 1 parasitic monopoles, properly placed in a linear array where only N directly‐fed monopoles are used, allow a broadside radiation and a gain value close to that of a standard printed array composed of 2 N + 1 directly‐fed elements. To verify the validity of the proposed design, prototype arrays for the S and C bands, composed of five‐ and nine‐monopoles, are simulated, fabricated and tested. In addition, it is demonstrated that a flat metal sheet placed at 0.25 λ 0 from the array board can further increase the directivity of about 3 dB; as a result, the measured gain is ∼10 dB for the five‐monopole array and 14 dB for the nine‐monopole array. Owing to their large fractional bandwidth (30%) and high gain, these monopole arrays may work as external antennas for high‐data‐rate point‐to‐point transmissions or for C‐band radar sensors.