Range focus lens

A test fixture for an electromagnetic test range comprising:

• a movable supporting structure;
• an electromagnetic radiation antenna mounted on said structure;
• a dielectric plane wave lens mounted on said structure in a fixed, spaced relation to said antenna, said lens being formed of a uniformly foamed plastic having a dielectric constant in the range of 1.05 to 1.5;
• a radiation-absorbing layer adjacent only the side of said lens adapted to face a test object;
• and
• radiation-absorbing material surrounding the radiation path between said antenna and said lens.

An electromagnetic test range comprising:

• a source of electromagnetic radiation;
• a test device;
• a dielectric plane wave lens between said source and said device, said lens being formed of a uniformly foamed plastic having a dielectric constant in the range of 1.05 to 1.5 and positioned to direct a plane wave to said device;
• first radiation-absorbing means surrounding the path between said source and said device for minimizing reflections and amplitude distortion;
• and
• second radiation-absorbing means adjacent said lens on the side of said test device only, said second absorbing means adapted to substantially eliminate wave re-reflections.

The method of testing electromagnetic devices under far-field conditions on an antenna range comprising:

• generating a test signal having a spherical wavefront at a first point,
• employing interception means to intercept said signal at a second point and convert same to a planar wavefront;
• intercepting the converted wavefront with the antenna to be tested;
• providing first radiation-absorbing means adjacent the path of said signal adapted to minimize amplitude distortion and reflection;
• said interception means comprising a plane wave lens constructed of a uniformly-foamed plastic having a dielectric constant in the range of 1.05 to 1.5;
• providing second radiation-absorbing means only on the side of said lens facing said tested antenna to absorb signals reflected from said antenna;
• and
• measuring predetermined properties of said device.