Determining a bearing to a radio beacon

A method of determining a bearing to a radio beacon, the method comprising:

• receiving, at each antenna system of an arrangement of radio antennas, a direct-sequence spread-spectrum radio signal, transmitted by a radio beacon, wherein the arrangement of radio antennas comprises a non-directional antenna system and one or more directional antenna systems, the non-directional antenna system having a receiving pattern that is omni-directional in a first plane, and each directional antenna system having a respective receiving pattern that is directional in a respective direction in the first plane;
• generating, for each antenna system, a respective digital signal from an electrical signal output by the antenna system in response to the radio signal;
• for each of the one or more directional antenna systems, performing a coherent despreading operation by coherently intercorrelating the digital signal from the directional antenna system with at least a portion of the digital signal from the non-directional antenna system to determine a correlation value for the directional antenna system;
• and
• processing the one or more determined correlation values to determine a bearing to the radio beacon relative to the arrangement of radio antennas.

A non-transitory computer-readable medium storing computer software for use in determining a bearing to a radio beacon, the computer software comprising instructions which, when executed on a processing system comprising one or more processors, cause the processing system to:

• receive at least one respective digital signal representative of at least a portion of a direct-sequence spread-spectrum radio signal, transmitted by a radio beacon and received at each antenna system of an arrangement of radio antennas, wherein the arrangement of radio antennas comprises a non-directional antenna system and one or more directional antenna systems, the non-directional antenna system having a receiving pattern that is omni-directional in a first plane, and each directional antenna system having a respective receiving pattern that is directional in a respective direction in the first plane;
• for each of the one or more directional antenna systems, perform a coherent despreading operation by coherently intercorrelating the digital signal from the directional antenna system with at least a portion of the digital signal from the non-directional antenna system to determine a correlation value for the directional antenna system;
• and
• output the one or more determined correlation values for further processing to determine a bearing to the radio beacon relative to the arrangement of radio antennas.