Calibrating radars and tracking space objects
Some of such technologies enable a technique for calibrating a radar based on using—A—an elemental antenna, which can be embedded on a housing hosting a set of antenna elements, or—B—an antenna mounted to a reflector ( 108 ). Some of such technologies enable a radar site containing a first ID phased array ( 112 ) and a second ID phased array ( 112 ), where the first ID phased array sends a set of signals and receives a set of reflections based on the set of signals, and the second ID phased array receives the set of reflections.
1. A radar calibration method comprising:
transmitting a signal from each of a plurality of phased array antennas and measuring a transmission phase for each transmitted signal as it is received at one or more calibration antennas, wherein one transmission phase is measured for each phased array antenna-calibration antenna combination;
receiving, from each of the one or more calibration antennas, a signal at each of the plurality of phased array antennas, and measuring a receive phase for each received signal at each of the plurality of phased array antennas, wherein one receive phase is measured for each phased array antenna-calibration antenna combination;
adjusting each measured transmission phase and each measured receive phase by a phase offset associated with a corresponding one of the one or more calibration antennas, where the phase offset associated with each one of the one or more calibration antennas is greater than or equal to zero;
calculating a single transmission phase correction for each of the plurality of phased array antennas, wherein the single transmission phase correction for a given one of the phased array antennas is based on a weighted average of the offset adjusted, measured transmission phases associated with the given one of the phased array antennas and the one or more calibration antennas;
calculating a single receive phase correction for each of the plurality of phased array antennas, wherein the single receive phase correction for a given one of the phased array antennas is based on a weighted average of the offset adjusted, measured receive phases associated with the given one of the phased array antennas and the one or more calibration antennas; and
storing the single transmission phase correction for each of the plurality of phased array antennas and the single receive phase correction for each of the plurality of phased array antennas for adjusting the phase of the plurality of phased array antennas during radar operations.
2. The method of claim 1 further comprising:
measuring a free-space phase offset for each phased array antenna-calibration antenna pair; and
further adjusting the measured transmission phase for each phased array antenna-calibration antenna pair and adjusting the measured receive phase for each phased array antenna-calibration antenna pair by the free-space offset measured for the corresponding phased array antenna-calibration antenna pair.
3. The method of claim 1 , wherein the plurality of phased array antennas are linearly aligned relative to each other.
4. The method of claim 3 , wherein the one or more calibration antennas are embedded on a surface of a radar reflector.
5. The method of claim 4 , wherein the number of calibration antennas is greater than 1, and wherein the calibration antennas are spaced apart from the plurality of phased array antennas.
6. The method of claim 5 , wherein the calibration antennas are linearly aligned and evenly dispersed relative to the plurality of phased array antennas.
7. The method of claim 6 , wherein the phase offset associated with each of the calibration antennas, other than a first one of the calibration antennas, is calculated relative to the phase offset of the first one of the calibration antennas and any calibration antennas located between that calibration antenna and the first calibration antenna.
8. The method of claim 7 , wherein the phase offset of the first one of the calibration antennas is zero.
9. The method of claim 7 , wherein calculating the phase offset of a given one of the calibration antennas, other than the first one of the calibration antennas comprises:
identifying a subset of the plurality of phased array antennas based on weighting factors associated with each of the phased array antennas in the subset, the given calibration antenna and the first calibration antenna or another calibration antenna adjacent to and between the given calibration antenna and the first calibration antenna;
transmit a signal from each of the phased array antennas in the subset, and measure a transmit phase at the given calibration antenna and the first or adjacent calibration antenna, and calculate a transmit phase difference value for each of the phased array antennas in the subset by subtracting the corresponding transmit phase measured at the given calibration antenna and the corresponding transmit phase measured at the first or adjacent calibration antenna; and
calculate a phase offset for the given calibration antenna based on a weighted average of the transmit phase difference values associated with the phased array antennas in the subset.
10. The method of claim 8 , wherein adjusting each measured transmission phase and each measured receive phase by a phase offset associated with a corresponding one of the calibration antennas comprises:
adding to each measured transmission phase and each measured receive phase the calculated phase offset of the corresponding one of the calibration antennas plus the calculated phase offset of any and all calibration antennas located between the corresponding one of the calibration antennas and the first calibration antenna.