Ultra Wideband Short Pulse Electromagnetics 4 Generation of High Power Subnanosecond Pulses Fundamental Physical Considerations for Ultrafast Spark Gap Switching Novel source of Powerful Subnanosecond Microwave Pulses Based on Superradiance Demonstration of Sub Millimeter Radiation Generation from Static Field by a Superluminous Ionization front in Semiconductor Capacitor Array About Mechanism of Wideband Microwave Radiation at Explosion of Condensed High Explosives Calorimetric Spectrometer for Measuring Single Microwave Pulses in Relativistic Microwave Electronics Devices Universal Sensor Using Electro Optic Sensing Principles Wave Equations and Transmission Formulas for the Output of a Receiving Antenna Energy Consideration in Space Time Synthesis of Collimated Pulsed Apertures Intermediate Field of an Impulse Radiating Antenna Aperture Efficiencies of Impulse Radiating Antennas Transient Gain of Antennas Related to the Traditional Continuous Wave (CW) Definition of Gain Ultra Wideband Sources and Antennas Multifunction Impulse Radiating Antennas: Theory and Experiment Antenna Source Integrated Ultra Wideband Electromagnetic Pulses Radiating Device Large Current Radiator for the Short Electromagnetic Pulses Radiation A New Broad Band Resistive Wire Antenna for Ultra Wide Band Applications Transient Behavior of Radiated and Received Fields Associated with a Resistively Loaded Dipole Multichannel Antenna Systems for Radiation of High Power Ultrawideband Pulses Ultra Wideband Duplexers for Low and High Peak Power Applications UWB Short Pulse Sensor for Target Electromagnetic Backscattering Characterization Synthesis of Purely Dielectric Transient Lenses Minimizing Dispersion in a Tem Waveguide Bend by a Layered Approximation of a Graded Dielectric Lens Simulation Modeling and Experimental Studies of High Gain Gallium Arsenide Photoconductive Switches for Ultra Wideband Applications Analysis of Nonlinear Optical Electromagnetic Interactions in Ultrafast Mode Locked Laser Diodes Ultra Wideband Analogue Channels Using Solitions Electronagnetic Impulse Response of Triply Distilled Water Ultrawideband Electromagnetic Pulse Propagation in Triply Distilled Water Pulsed Beam Propagation in Lossless Dispersive Media Spectral Alternatives for the Synthesis of Short Pulse Wavefields in Waveguides Space Time Green Function and Short Pulse Propagation in Different Media Propagation of Ultrawideband Pulsed Radiation in Conducting Medium Passage of Short Pulse Throughout Oscillating Circuit with Dielectric in Condenser UWB Measurements of Canonical Targets and RCS Determination Dual Polarized UWB Radar Measurements of the Sea at 9 GHZ Direct Construction of a  Pulse from Natural Frequencies and Evaluation of the Late Time Residuals A Mixed Time Frequency Scale Analysis of the Hybrid Wavefront Resonance Representation Joint Physical Optics and FDTD Analysis of Microwave Scattering Towards a Theory of Submarine Mast Detection Radio Frequency Interferences Suppression for Noisy Ultra Wide Band SAR Measurements The Problems of Small Base Ultrawideband Radar Time Frequency Analysis and Noise Suppression with Shift Invariant Wavelet Packets Summary of the DARPA Background Clutter Data Collection Experiment Numerical and Measurement Based Study of the Resonance Frequency Technique to Detect Anti Personnel Mines Feasibility Study into the Identification of Landmines Using UWB Radar: An Analysis Using Synthesized Data Ultra Wideband Synthetic Aperture Radar for Mine Field Detection Modification of the Aperture Synthesizing Method for Underground Sounding Data Processing Time Focusing of Electromagnetic Sounding in Conductive Media Using Similarities between Wave and Diffusion Propagation. In the tradition of the previous three conferences the proceedings of the 4th Ultra Wideband Short Pulse Electromagnetics Conference explores topics including pulse generation and detection; broadband electronic systems; antennas theory design experiments and systems; pulse propagation; scattering theory; signal processing; and buried targets detection and identification.