Phased Array antennas are satellite’s Holy Grail
September 17, 2020
The normal buyers of Phased Array satellite antennas are usually the military or public-service operators, or aircraft, train or bus operators. Their budgets can afford the thousands of dollars for a single installation. But if the plans of SpaceX (and rivals OneWeb and Project Kuiper) are to have any mass-market consumer impact, these costs must come crashing down to around $100 or less.
On September 8th the US Patent Office granted Space Exploration Technologies (the full name of SpaceX) a Patent (Number: 10,770,790) and inventor – and SpaceX staffer – Alireza Mahanfar to cover “uni-dimensional steering of phased array antennas” as far as the ground-based device is concerned. The Patent application was made in February 2018.
The challenge for SpaceX’s Starlink system is that its Low Earth Orbiting (LEO) satellites are moving very quickly across the sky and the receiver has to be able to ‘move’ very quickly to pick up the following satellite as the first drops over the horizon.
The design calls for multiple receiving elements which can be pointed in a particular direction electronically.
The full Patent grant in its summary, says: “In accordance with one embodiment of the present disclosure, a phased array antenna system configured for communication with a satellite that emits or receives radio frequency (RF) signals and has a repeating ground track in a first direction is provided. The antenna system includes: a phased array antenna including a plurality of antenna elements distributed in a plurality of M columns oriented in the first direction and a plurality of N rows extending in a second direction normal to the first direction, and a plurality of fixed phase shifters aligned for phase offsets between antenna elements in the first direction; and a gain-enhancement system configured for gain enhancement in the second direction of radio frequency signals received by and emitted from the phased array antenna.”
In essence, the device focuses not on the whole sky but one orbital plane (where their satellites are operating). By leveraging their beam forming in such a way that they only talk to a single arc of sky, thus increasing RF signal strength.