Abstract: An exponential impedance matching method is used to optimize the structure of constant impedance TEM horn used in ultra-wide spectrum radiation system. Both the constant impedance TEM horn and the ridged TEM horn have been fabricated and tested under Gaussian pulses of about 1 ns duration. The simulation and experiment results indicate that the radiation factor on the principal axis has been improved by the introduction of ridge. When the reflector impulse radiation antenna (IRA) is fed by a ridged TEM horn, the distribution of the electric fields peak intensity on the reflector is intensified, and the symmetry of electric field on the reflector and the radiation factor of the reflector IRA are improved.