The generation of ultra-wideband (UWB) pulses is a challenging problem that involves generating pulses with fast rise times on the order of 100 ps and voltages of more than 500 kV. Pulsewidths from 130 ps to a few nanoseconds (ns) are possible. A critical step involves switching high voltages with precision. The use of both gas and oil for the switching medium has been accomplished with varying results. The Air Force Research Laboratory (AFRL) is pursuing both media in the gas-switched H-series of pulsers and in studies of oil switches that promise good performance in compact packages. We are also pursuing solid-state switched systems that have demonstrated the potential for use in compact systems and in transient antenna arrays with steerable beams. This paper reviews recent progress in fast, high voltage switching and UWB transmitter development. These UWB pulsers and antennas have the potential for use in transient radar, target identification, and communications. Index Terms-Brewster angle window, gas switch, high power microwave, impulse radiating antenna, oil switch, photoconductive solid-state switch, radio frequency lens, silicon avalanche shaper, spark gap switch, transient antenna, ultra-wideband. I. BACKGROUND U LTRA-WIDEBAND (UWB) sources and antennas are of interest for a variety of potential applications that range from transient radar systems to communications systems. Predating the recent technology developments of the last several years were a number of important discoveries in the 1980's that led to the first UWB pulsers capable of transmitting high peak field signals through a variety of antennas. The Bournlea pulse generator is a good example of an instrument that is capable of fast rise times and a high repetition rate [1]. Using a CX1599 hydrogen thyratron as its basis, the original Bournlea pulser, made in 1986, could produce a 5-kV pulse with a rise time of 3 ns and a pulse repetition frequency (PRF) Manuscript