Geolocation of radio frequency devices using spaceborne phased arrays
A communication system has a phased antenna array configured to communicate via a plurality of beams with a wireless device, such as user equipment (e.g., a smart phone). The plurality of beams defines a field of view of the phased antenna array, the field of view having a plurality of cells and each of the plurality of beams is associated with one of the plurality of cells within the field of view. A processing device detects the wireless device within the field of view and determines a coarse geographic location of the wireless device within the field of view of the wireless device when the wireless device is within the field of view, or within a cell. The system further determines a fine geographic location for the wireless device based on frequency offset (due to Doppler) and signal flight time.
1. A satellite communication system, comprising:
one or more low Earth orbit (LEO) satellites having a phased antenna array configured to provide a plurality of beams for communication within a field of view, the field of view having a plurality of cells and each of the plurality of beams is associated with one of the plurality of cells within the field of view; and
one or more delay compensators configured to perform delay compensation on signals relative to a beam center for each respective beam of the plurality of beams;
wherein the phased antenna array is configured to receive a signal from a wireless device via one of the plurality of beams and is configured to detect that the signal is within a specific one of the plurality of cells within the field of view based upon the delay compensation; and
wherein the one or more LEO satellites include:
a central processor configured to take data from individual beams of the plurality of beams and package the data into a combined signal; and
a communication antenna separate from the phased antenna array, the communication antenna configured to transmit the combined signal to a ground station separate from the wireless device.
2. The satellite communication system of claim 1 , wherein the one or more delay compensators are part of a ground processor located remote from the one or more LEO satellites.
3. The satellite communication system of claim 1 , further comprising a beamformer that is configured to isolate the signal to the specific one of the plurality of cells within the field of view.
4. The satellite communication system of claim 1 , further comprising one or more processing devices configured to determine a coarse geographic location of the wireless device within the field of view.
5. The satellite communication system of claim 4 , wherein the one or more processing devices are further configured to determine a fine geographic location of the wireless device based on at least one of iso-Doppler or iso-delay of the received signal.
6. The satellite communication system of claim 1 , wherein the delay compensation is performed so as to obtain an approximately constant or a fixed delay.
7. The satellite communication system of claim 1 , wherein the one or more LEO satellites is a constellation of a plurality of satellites having the phased antenna array.
8. A method for satellite communication, the method comprising:
providing, via one or more low Earth orbit (LEO) satellites having a phased antenna array, a plurality of beams for communication within a field of view, the field of view having a plurality of cells and each of the plurality of beams is associated with one of the plurality of cells within the field of view;
receiving, by the phased antenna array, signals from one or more wireless devices via one or more of the plurality of beams;
performing, by one or more delay compensators, delay compensation on the signals relative to a beam center for respective beams of the plurality of beams;
detecting that one or more of the signals are within specific ones of the plurality of cells within the field of view based upon the delay compensation;
combining data from individual beams of the plurality of beams into a combined signal; and
transmitting, via a communication antenna separate from the phased antenna array, the combined signal to a ground station separate from the wireless device.
9. The method of claim 8 , further comprising isolating, via a beamformer, the signals to the specific ones of the plurality of cells within the field of view.
10. The method of claim 8 , further comprising determining a coarse geographic location of at least one of the wireless devices within the field of view.
11. The method of claim 10 , further comprising determining a fine geographic location of the at least one wireless device based on at least one of iso-Doppler or iso-delay of the received signals.