Enhancing Antenna Radiation Gain with an Improved Half-Fisheye Lens

An improved half-fisheye lens (HFL) is designed for high-gain lens antennas applications. To control the profile height of the lens and reduce its refractive index, the HFL is axially compressed, and its refractive index distribution modified. Additionally, to achieve plane wave emission under practical feeding conditions and relieve the impedance mismatch at the interface between the HFL and free space, a transition layer with a specific shape and refractive index distribution is designed at the interface. When feeding with a standard horn antenna, the improved HFL achieves a radiation gain improvement of 1.8 dB compared to the conventional HFL, while reducing the maximum refractive index from 2 to 1.6.