Scanning range extension by combining arrays with lenses

Sammanfattning: Array antennas, and more specifically phased array antennas, are widely used in radar detection and communication systems because of their excellent beam scanning ability and simple control. Generally speaking, the scanning function can be realized in two ways: mechanically or electronically. Mechanical steering is done by rotating the whole structure, so there is a certain delay. The electronic scanning is done by controlling the relative relationship between the input signals of different array elements. Electronical scanning is then faster and easy to integrate with other circuits, which makes it an interesting solution to these applications. However, the disadvantage of electronic steering is that the scanning angle range is limited, which is generally within the range of ±60° . Beyond this range, the performance of the antenna will decrease considerably. One way to improve the antenna gain or expand the scanning range of the array antenna is to combine the array antenna with a dielectric radome. This thesis mainly studies how to adjust the shape of the dielectric radome with a center frequency of 28GHz to expand the beam scanning range of the two-dimensional array composed of rectangular waveguide ports. The inner and outer profiles of the dielectric lens follows the conics equation, and the shape of the lens can be controlled by adjusting different parameters. In this thesis, I adjust the lens shape according to three different objectives: 1. Increase the gain of the array antenna at the small scanning angle (0° ∼ 30°). The adjusted lens model increases the gain in this range by about 0.5 dBi; 2. Improve the gain of the array antenna at the large scanning angle (60° ∼ 80°). The final lens model increases the gain of the array antenna at the scanning angle of 70° and 80° by about 0.5 dBi and 1 dBi respectively; and 3. Improve the directivity of the array antenna in the range of 0° ∼ 70° . The final dielectric lens model improves the directivity in the broadside direction by about 1 dBi, and increases about 0.6 dBi when the scanning angle is 60° ;