A Spherically Conformal Transmit-Array Antenna with High Gain and Steerable Beams

This paper presents a spherically conformal transmit-array (SCTA) antenna with high gain and 1D steerable beam, which is very favorable for high-speed aircraft applications. The SCTA consists of 5×5 uniform-sized transmit-subarrays (TSA) with five distinct beam directions; and each TSA contains 6×6 square loop as the unit cells of the multi-layer frequency selective surface. When the TSAs are illuminated by a mechanically rotated feed source, the SCTA synthesizes a high-directivity beam according to the TSAs’ directions. To achieve good aerodynamic characteristics, a novel spherical topology with strategic array arrangement is proposed. Then, detailed derivations and analyses are conducted to calculate the transmission phases of all the unit cells. To validate the designs, a prototype of the SCTA was fabricated and measured. Experimental results show the designed SCTA achieves a high gain of about 20 dBi and a 1D beam scanning range of ±15°, making it very suitable for aircraft-based wireless communication applications or radar systems.