Slot antenna

A slot antenna comprising a dielectric substrate, a high-frequency signal transmission line formed on one surface of said dielectric substrate and having an open end, and a ground layer formed on the other surface of said dielectric substrate, said ground layer having a slot at a position opposed to the open end of said transmission line, wherein

• a dielectric plate for impedance matching is laminated on the surface of said ground layer on the side where said slot is formed so as to cover said slot, and
• wherein the length ML (mm) from the open end of said transmission line to a portion corresponding to the center of said slot, and the length SL (mm) of said slot in a direction at right angles with the direction in which said transmission line extends, satisfy the conditions represented by the following formulas (2) and (3):
• 62.7/(f·∈2½)≦ML≦125/(f·∈2½) (2)
• 171/[(f·[(∈1+∈2)/2]½]≦SL≦250/(f·[(∈1+∈2)/2]½] (3)
• where ∈1 is a dielectric constant of the dielectric plate for impedance matching, and ∈2 is a dielectric constant of the dielectric substrate, and f is a frequency (GHz) of the transmitted signals.