Reduced beamwidth antenna

1. An antenna system having a reduced beamwidth, comprising:

an evanescent field generator that generates an evanescent field, resulting in the restoration of high spatial frequency components to a far field radio frequency (RF) signal received at the antenna system;

a negative refractive index lens assembly that focuses the evanescent field onto a focal plane; and

an RF detector assembly located in the focal plane, that detects the amplified evanescent field.

2. The system of claim 1 , the evanescent field generator comprising a plate with a plurality of apertures arranged in a grid as to spatially sample the far field RF signal, where the diameter and effective path length of each of the plurality of apertures being selected to apply a desired complex gain to the far field RF signal at the aperture.

3. The system of claim 2 , at least one of the plurality of apertures being filled with a dielectric material as to provide the selected effective path length at the at least one aperture.

4. The system of claim 1 , the RF detector assembly comprising an array of fractional wavelength RF antennas to create a multiple-beam beamformer.

5. The system of claim 1 , the negative refractive index lens assembly comprising:

a first array of planar lenses, aligned along a first direction as to focus the evanescent field into respective intermediate fields; and

a second array of planar lens, aligned along a second direction as to focus the intermediate fields into a single focal point having a width less than a wavelength of the RF signal.

6. The system of claim 5 , wherein each planar lens of the first and second arrays of planar lenses comprises a circuit board with at least one transmission line.

7. The system of claim 1 , further comprising a signal preconditioning element that directs RF energy to the evanescent field generator.

8. A method for detecting a far field RF signal, comprising:

spatially filtering a far field RF signal to restore high spatial frequency components to the far field RF signal to produce an evanescent field;

focusing the evanescent field onto a focal plane; and

detecting the focused evanescent field in the focal plane.

9. The method of claim 8 , wherein focusing the evanescent field onto the focal plane comprises focusing the evanescent field at a negative refractive index lens.

10. The method of claim 8 , wherein filtering a far field RF signal comprises directing the far field RF signal at a mask comprising a plurality of apertures, where the diameter and effective path length of each of the plurality of apertures is selected to apply a desired transfer function to the far field RF signal.

11. The method of claim 8 , wherein focusing the evanescent field comprises focusing the evanescent field to an intermediate field along a transverse axis at a first lens assembly and focusing the intermediate field to a focal point in the focal plane at a second lens assembly.