Antenna systems with beam forming and beam steering capabilities for HF skywave radars

Radiation characteristics of linearly phased, periodic, planar dipole arrays, which can be used as transmitting/receiving antenna systems for HF skywave radars, are investigated. Rectangular, triangular and trapezoidal arrays are proposed in obtaining different beam shapes in the desired directions. Beam steering is achieved by adjusting the inter-element phase increments coherently. The effects of vertical array-tilt with a desired take-off angle (TOA) a are presented by a number of radiation pattern examples. The ground effect is investigated using the image theory by assuming the Earth s surface as perfectly electric conductor (PEC). Radiated fields are obtained using Floquet wave representations plus the synthetic aperture approach. Validation is done against element-by-element summation representations