Experimental Studies of Scale - Model and Full - Scale IRAs Mounted on Parachutes

We investigate here a number of variations of the Para-IRA, which is an Impulse Radiating Antenna configured for parachute delivery. We consider first two scale models of the Para-IRA with aluminum reflectors, and then we consider a full-scale version built from fabric. In the scale models, we first investigate the effect of using a large F/D ratio in an IRA. We then investigate the effect of using a trimmed reflector, with portions of the reflector removed that contribute destructively to the radiated field. Two scale model antennas with aluminum reflectors were built with F/D = 1.0 and with radius = 46 cm (18 in.). These antennas were configured with so-called “non-floppy” feed arms, which are contained entirely within the aperture. One antenna had a complete circular reflector, and the other had a trimmed reflector. Experimental data from these two designs are compared to data from earlier designs. We also built and tested a fabric version of the Para-IRA, which had a number of improvements over earlier versions.