Variable Impedance Feed Structure for Impulse Radiating Antenna

We present in this work, an alternative design for the TEM feeding structure of the Impulse Radiating Antenna (IRA). The variation here proposed consists of a set of TEM feeders whose impedance changes as a function of the radial distance measured from the focal point towards the parabolic reflector. This changes the aperture of the electric field at the aperture of the reflector, in a factor given as the square root of the ratio between the terminal impedance and the initial impedance, hence changing the amplitude of the radiated field in the same proportion. The second benefit of this design is that it allows the adaption of low-impedance voltage generators to the IRA. The drawback of this design is that it limits the low frequency content of the radiated pulse [1], but this will not impact the performance of small reflectors, which are unable of radiating low frequency components. For the specific case of the present paper, we propose an exponentially varying TEM impedance as follows [2]