Near Field Focusing Using Phase Conjugating Impedance Loaded Wire Lens

The properties of a lumped loaded wire array as a means for near field focusing using phase conjugation is studied. The constructive role of phase conjugation in the near field image formation is justified both analytically and numerically. The generation of phase conjugated energy and how this is influenced by lumped impedance loading of the wires constituting the lens is discussed. In particular it is shown that inductive loading of the constituent lens wire elements is essential for subwavelength focusing since this leads to the creation of a phase conjugated near field predominantly determined by a convolution of the array current distribution with the real part of the Greens function which oscillates at a subwavelength scale. The characteristic resolution of the lens in terms of the full width at half maximum is shown to be ~ λ/7 for a single source and better than λ/4 for two dipole sources at λ/10 source-lens separation distance.