Wide-Scan Focal Plane Arrays for mmWave Point-to-Multipoint Communications

A new antenna system concept is presented where a wide-scan focal plane array antenna is used to achieve point-to-multipoint communication. The focal plane of a parabolic toroid reflector is populated with several antenna arrays, the positions of which determine the directions of the beams. This concept is investigated for beams pointed towards 0° (broadside) and 28° in azimuth. Each array allows for scanning an additional ±1° in azimuth and elevation. This allows for compensation of twist and sway of the antenna mast. Several array configurations are compared in terms of directivity and scan loss for such a system at E-band. It is found that an 8-by-8 array with an inter-element spacing of 0.7λ0 results in an optimal directivity with a scan loss lower than 1dB when scanning ±1° in azimuth and elevation. For the 0° beam direction the directivity is 45.5dBi and for the 28° beam direction the directivity is 44.4dBi, showing the wide angle scanning properties of this system. An experimental system is built at K-band and measurements are performed showing this system in action. In the measurements an array of 8-by-8 is used with an inter-element spacing of 0.5λ0 . The scan loss when scanning ±2° in azimuth and elevation is below 1dB. The directivity is 37.0dBi and 35.4dBi for the 0° and 28° beam directions, respectively. The spillover losses and aperture efficiencies are also found, as well as a relative metric for the transmitted power and the effective isotropic radiated power for both the E-band and K-band systems.