Analysis of Bandwidth and Field-of-View Improvement Techniques for Satellite Communication Phased Arrays in Ka Band

Kurzfassung

Satellite communication with LEO-constellations and for the purpose of mobile applications, like in avionic, require antennas with the ability to track the relative movement of satellites. Phased arrays offer this ability without necessitating mechanical rotation. Microstrip patch antennas offer multiple advantages for the application in such arrays, but typically achieve only a narrow impedance bandwidth. Thus, their application in broadband communication is difficult. Furthermore, planar arrays exhibit a limited field-of-view that reduces the tracking capability of the array. This thesis investigates the increase of bandwidth for receiver patch antennas in the ITU Ka downlink band from 17.7 GHz to 21.2 GHz. Stacked patches and a quadrature hybrid coupler are employed to design a dual circularly polarized patch antenna, which is manufactured and measured. The antenna fulfills both a −10 dB limit for the S-parameters and a 3 dB limit for the axial ratio from 18.62 GHz to 20.86 GHz. This corresponds to a bandwidth of 11.3 %. Compared to a patch antenna used as starting point and already available at DLR, the bandwidth is improved by 50 %. Moreover, conformal array architectures are analyzed for their ability to increase the field-of-view. Selected 1-dimensional conformal architectures are compared. Good results are obtained for faceted architectures with three or four facets. By using a truncated pyramid architecture, the field-of-view is increased from ±42° for planar architectures to ±70° for all azimuth directions. The axial ratio in the steered beam is strongly improved compared to planar arrays.