A wide band low profile dual-pol "Thumbtack" array
A dual-pol array of 15×15 “Thumbtack” elements was built and tested for 0.5-2.0 GHz demonstration. The array is 3 in. (7.6 cm) thick, a bout 1/8 wavelength at the low end of the band, characterized by a high impedance (~300 ohms) aperture, matching to free space's wave impedance (377 ohms) directly without a long flare as in a Vivaldi notch. The array has a square lattice of 3 in. (7.6 cm) spacing, and the “Thumbtack” element has a coincident and stationary phase center. The thin and planar structure produces ver y low X-pol, typically 30 dB down at bore-sight, and 15 dB at 45° of axis along the diagonal cut. The array was designed fo r applications that require na nosecond rise time, ultra low X-pol and non-dispersive phase response. These unique features make it possible to produce sharp images for IED detection, FOP EN SAR, see-through-the wa ll radars, a nd other EW missions.