A balun, generally including a substrate, a microstrip conductor, and a parallel strip conductor is described, where a characteristic impedance of the balun is substantially constant at each cross-sectional point along a length of the balun. A transverse electromagnetic horn antenna can transmit and receive ultra-wide band pulses, and includes a first metal conductor and a second metal conductor, where a characteristic impedance of the first and second conductor varies over a length of the antenna in a controlled means.