Design of a near-field-focused substrate integrated planar array antenna

A X-band multi-layer near-field-focused antenna (NFFA) is developed on the basis of substrate integrated waveguide (SIW) technology and fabricated through PCB process. Several metallic vias with different diameters, which are equivalent to open-ended air-filled circular waveguides, are fabricated to form phase shifters and radiating elements at the same time. They are fed by an SIW wideband feeding network underneath these radiating elements to achieve a compact configuration. Between the radiating and feeding layers, there exists a separated matching layer to achieve a good reflection characteristic. As an example, a 4×4 NFFA prototype is fabricated and measure. The maximum intensity of the electric field is at 150 mm. The measured results are in good agreement with the simulated ones near the focal distance.