APPROACH/DESIGN OF HIGH GAIN BROADBAND ANTENNAS; FAST-RISETIME APPLICATIONS

THE RADIATION OF A NARROW BEAM OF ELECTROMAGNETIC FIELDS OVER A BROAD SPECTRUM OF FREQUENCIES CONTAINED IN A FAST PULSE IS AN IMPORTANT PROBLEM IN ANTENNA THEORY. IMPULSE RADIATING ANTENNAS (IRAS) ARE OF INTEREST IN THIS SOLICITATION. WE PROPOSE TO STUDY A RADIATING TEM HORN AND A REFLECTOR ANTENNA FED BY A TEM HORN, TO BROADCAST THE FAST-RISETIME PULSE. ONE BEGINS WITH AN APERTURE FORMULATION OF THE ANTENNA RADIATION, BY SPECIFYING THE TANGENTIAL ELECTRIC FIELD ON THE APERTURE. THIS APERTURE FIELD PRESCRIPTION WILL BE DETERMINED IN BOTH CASES BY DETAILED CALCULATIONS. FOR AN APERTURE ILLUMINATION THAT IS LIKE A STEP FUNCTION, THE RESULTING FAR FIELD IS IMPULSE-LIKE. THE WIDTH OF THE IMPULSE BECOMES VERY NARROW AS ONE APPROACHES THE PRESCRIBED DIRECTION OF FOCUS. PRACTICAL CONSIDERATIONS OF FEED, IMPEDANCE, BREAKDOWN STRENGTHS WILL BE CONSIDERED IN OUR DESIGN STUDY OF THESE TWO CANDIDATE ANTENNAS.