Abstract: A miniature anechoic changer for testing antennas capable of producing radio frequency energy with a planar wavefront substantially uniform and free of distortion is shown. The chamber is comprised of a source antenna located in the near field of the test antenna radiating radio frequency energy having a wavefront with an amplitude having a distribution pattern that approximates (SIN X)/X and a lens having a focal point mounted such that the focal point of the lens is located in the center of the source antenna. As the source antenna radiates energy the energy passing through the lens is converted from a spherical wavefront to a planar wavefront substantially uniform and free of distortion.

Abstract: A circulator for duplexing microwave signals is shown to consist of a pair of folded magic-T hybrid junctions with a nonreciprocal phase shift section disposed between the parallel ports of such junctions, the nonreciprocal phase shift section being made up of U-shaped ferrites supported between the insides of H-plane walls in a rectangular waveguide and U-shaped permanent magnets adjustably supported on the outsides of the H-plane walls so that the magnetic flux in the U-shaped ferrites may be changed as required.