1. An antenna array assembly, comprising:
a ground plate;
a linear array of patch radiator elements disposed in a spaced parallel relationship with a first face of the ground plate; and
a first and second elongate passive radiator each comprising one or more substantially planar conductive parts disposed to be generally upstanding in relation to the first face of the ground plate and being electrically isolated from the ground plate, the first and second elongate passive radiators being disposed symmetrically on either side of the linear array and parallel to a centre line of the linear array, on the same side of the ground plate as the linear array;
a third and fourth elongate passive radiator each comprising one or more substantially planar conductive parts disposed to be generally upstanding in relation to to the first face of the ground plate and being electrically isolated from the ground plate, the third and fourth elongate passive radiators being disposed symmetrically on either side of the linear array and parallel to the centre line of the linear array, on the same side of the ground plate as the linear array, and further from the linear array than are the first and second elongate passive radiators,
wherein a width of each of the first and second elongate passive radiators measured in a direction pointing away from the first face of the ground plate is greater than a width of each of the third and fourth elongate passive radiators measured in a direction pointing away from the first face of the ground plate, and
wherein each of the each of the third and fourth elongate passive radiators is spaced from the first face of the ground plate by a first distance such that each of the third and fourth elongate passive radiators projects further from the ground plate than does each of the first and second elongate passive radiators.

2. An antenna array assembly according to claim 1, wherein the width of each of the first and second elongate passive radiators is in the range 0.4 to 0.6 wavelengths at a operating frequency of the antenna array assembly and the width of each of the third and fourth elongate passive radiators is in the range 0.2 to 0.4 wavelengths at a operating frequency of the antenna array assembly.
3. An antenna array assembly according to claim 1, wherein the width of each of the first and second elongate passive radiators is substantially half a wavelength at at least one operating frequency of the antenna array assembly and the width of each of the third and fourth elongate passive radiators is substantially a quarter wavelength at at least one operating frequency of the antenna array assembly.
4. An antenna array assembly according to any preceding claim, each of the first and second elongate passive radiators is disposed 0.4 to 0.6 wavelengths away from the centre line of the linear array of patch radiator elements at a operating frequency of the antenna array assembly and each of the third and fourth elongate passive radiators is disposed 0.8 to 1.2 wavelengths away from the centre line of the linear array of patch radiator elements at at least one operating frequency of the antenna array assembly.
5. An antenna array assembly according to any preceding claim, each of the first and second elongate passive radiators is disposed substantially half a wavelength away from the centre line of the linear array of patch radiator elements at at least one operating frequency of the antenna array assembly and each of the third and fourth elongate passive radiators is disposed substantially one wavelength away from the centre line of the linear array of patch radiator elements.

6. An antenna array assembly according to any preceding claim
comprising a fifth and sixth elongate passive radiator each comprising one or
more substantially planar conductive parts disposed to be generally upstanding
in relation to the first face of the ground plate and being electrically isolated
from the ground plate, the fifth and sixth elongate passive radiators being
disposed symmetrically on either side of the linear array and parallel to the
centre line of the linear array, on the same side of the ground plate as the linear
array, and further from the linear array than are the first and second elongate
passive radiators,
wherein each of the each of the fifth and sixth elongate passive radiators is spaced from the first face of the ground plate by a second distance such that each of the first and second elongate passive radiators projects further from the ground plate than does each of the fifth and sixth elongate passive radiators.
7. An antenna array assembly according to claim 6, wherein each of the fifth and sixth elongate passive radiators has a width in the range 0.2 to 0.4 wavelengths at at least one operating frequency of the antenna array assembly.
8. An antenna array assembly according to claim 6, wherein each of the fifth and sixth elongate passive radiators has a width of substantially a quarter wavelength at at least one operating frequency of the antenna array assembly.
9. An antenna array assembly according to any preceding claim, wherein at least some of the respective substantially planar conductive parts of the first and second elongate passive radiators are arranged in a respective zigzag arrangement in a cross-section taken in a plane parallel to the first face of the ground plane,
10. An antenna array assembly according to claim 9, wherein each of the first and second elongate passive radiators is inclined towards the linear

array of patch radiator elements by an angle of less than 10 degrees from perpendicular to the first face of the ground plate.
11. An antenna array assembly according to claim 9, wherein each of the third and fourth elongate passive radiators is inclined towards the linear array of patch radiator elements by an angle of less than 10 degrees to from perpendicular to the first face of the ground plate.
12. An antenna array assembly according to any preceding claim, comprising a first and second elongate conductive wall each being disposed symmetrically on either side of the linear array and parallel to the centre line of the linear array, on the same side of the ground plate as the linear array, and closer to the linear array than are the first and second elongate passive radiators, wherein the first and second elongate conductive walls are electrically connected to the first face of the ground plate and are substantially perpendicular to the first face of the ground plate, protruding from the ground plate by less than a quarter of a wavelength at at least one operating frequency of the antenna array assembly.
13. An antenna array assembly according to any preceding claim, wherein the ground plate comprises a base plate to which the first and second elongate passive radiators are mounted and a raised section disposed between the base plate and the patch radiator elements comprising at least part of the first face of the ground plate.
14. An antenna array assembly according to any preceding claim, wherein the first and second elongate passive radiators are mounted on the ground plate by insulating fixings.
15. An antenna array assembly according to any preceding claim, wherein each patch radiator element comprises a first planar part disposed in a

spaced parallel relationship to the first face of the ground plate and a second planar part disposed in a spaced parallel relationship to the first planar part, on the side of the first planar part away from the first face of the ground plate.
16. An antenna array assembly according to any preceding claim,
wherein each patch radiator element is configured to radiate at orthogonal
polarisations substantially +/- 45 degrees to the centre line of the linear array.
17. An antenna array assembly according to any preceding claim, wherein the third and fourth elongate passive radiators are attached to a radome covering the antenna array assembly.
18. An antenna array assembly according to any preceding claim, wherein the edge of each of the third and fourth elongate passive radiators closest to the first face of the ground plate are substantially the same distance from the first face of the ground plate as are the edges of the first and second elongate passive radiators furthest from the first face of the first face of the ground plate.
19. An antenna array assembly according to any preceding claims, wherein each of the first and second elongate passive radiators is composed of a series of sections, each comprising one or more substantially planar conductive parts, wherein a gap is provided between each section of 0.2 to 0.4 wavelengths at at least one operating frequency of the antenna array assembly.
20. An antenna array assembly according to any preceding claims, wherein each of the first and second elongate passive radiators is composed of a series of sections, each comprising one or more substantially planar conductive parts, wherein a gap is provided between each section of substantially a quarter wavelength at at least one operating frequency of the antenna array assembly

21. An antenna array assembly according to claim 19 or claim 20, wherein each section has a length measured in a direction parallel to the centre line of the linear array in the range 0.4 to 0.6 wavelengths at at least one operating frequency of the antenna array assembly.
22. An antenna array assembly according to claim 19 or claim 20, wherein each section has a length measured in a direction parallel to the centre line of the linear array of substantially a half wavelength at at least one operating frequency of the antenna array assembly.