The present invention relates to a compact slot antenna formed, in a multilayer substrate comprising, in order, at least one first conductive layer, a first dielectric layer, a second conductive layer, a second dielectric layer and a third conductive layer, of a first slot-line realized in the second conductive layer, said first slot-line being connected to the supply of the antenna, of a second and a third slot-lines realized respectively in the first and in the third conductive layers, the second and third slot-lines each being delimited by two conductive strips of which a first extremity, supply side, is interconnected by a via passing through a window realized in the second conductive layer and a second extremity connected to the second conductive layer, both conductive strips on the side of the second extremity being, either in open circuit, or in short circuit, the electrical length of the first, second and third slot-lines being a function of the wavelength at the operating frequency of the antenna.