Abstract: Based on 2.1 m diameter parabolic reflector, the parameters of TEM horn-feed and coplanar-feed IRA were optimized, and the characteristics of these two antennas were compared in this paper. A physical model of IRA was built and the radiation center movement principle of V-shaped dipole was investigated. The analytic radiating solution of these two antennas was got by different approximation measurement. From theoretic calculation and numerical simulation, the field distribution of the reflector aperture was obtained. And with different width of excitation impulse, the radiation waveform of these two antennas exhibited regular transformation. With GW peak power capacity, the TEM horn and coplanar-feed IRA were fabricated. The experiment results agree well with the conclusion achieved above.