A near-field probe for subwavelength-focused imaging

A near-field antenna array probe is presented that can produce a subwavelength focal spot at a distance of 0.25lambda. The array is composed of a central fed dipole with loaded secondary dipoles placed less than half a wavelength away on each side. When performing a surface raster scan, the probe return loss can be monitored to detect the presence of small wire loops with subwavelength resolution. An experiment was simulated to scan for two loops placed 0.25lambda away from the probe and separated by 0.4lambda. The array probe was able to clearly resolve both loops while a single dipole probe could not. The minimum resolvable loop separation was 0.3lambda for the array probe and 0.65lambda for the single dipole probe.