There is provided an apparatus comprising an antenna (105) configured to receive a signal from a global navigation satellite system, wherein the antenna includes a first feed and a second feed; a hybrid coupler (110) including a first hybrid input, a second hybrid input, a first hybrid output, a second hybrid output, and wherein the first hybrid output is shifted in phase by 90 degrees relative to the second hybrid output; a variable phase shifter (150) including a shifter input and a shifter output, hybrid output; and a combiner (155) including a first combiner input, a second combiner input, and a combiner output, wherein the first combiner input is coupled to the shifter output, and the second combiner input is coupled to the second hybrid output, and wherein the combiner output is provided to detection circuitry (197).