Use of isorefractive media to improve prompt aperture efficiency in a lens IRA

The concept of prompt aperture efficiency is introduced for impulse radiating antennas (IRA's) and the efficiency is analyzed in detail for a specific class of lens IRA's. By using two isorefractive media, one with a low impedance within the aperture of the IRA and one with a high impedance outside the aperture, the power on the TEM transmission line-feed structure of the IRA can be concentrated within the aperture, thereby improving the prompt aperture efficiency beyond what is possible using a single medium.