A slot antenna consists of a metal surface, usually a flat plate, with a hole or slot cut out. When the plate is driven as an antenna by a driving frequency, the slot radiates electromagnetic waves in similar way to a dipole antenna. The shape and size of the slot, as well as the driving frequency, determine the radiation distribution pattern. Slot antennas are often used instead of line antennas when greater control of the radiation pattern is required. Slot antennas are often found in standard desktop microwave sources used for research purposes.
A slot antenna's main advantages are its size, design simplicity, robustness, and convenient adaptation to mass production using PC board technology.
The slot antenna was invented in 1938 by Alan Blumlein, while working for EMI. He invented it in order to produce a practical type of antenna for VHF television broadcasting that would have horizontal polarization, an omni-directional horizontal radiation pattern and a narrow vertical radiation pattern