Communication Problems for Transient Signals

Abstract

In considering transient electromagnetics, one has to emphasize the successes in the generation of solitary waveforms in the following ranges of time scales

• 1 Nanosecond range. With advances in ultrafast gallium arsenide switches, new possibilities had been opened in the elaboration of ultrabandwidth (UBW) radar operating with single-cycle nanosecond pulses. These impulse waveforms required the fundamental redesign of radiators (e.g., shaping of waveforms by conical antenna (Shen et al., 1988) and receivers (bended L-antenna (Shen et al., 1990)). Moreover, such broadband pulses have stimulated the development of methods of target identification owing to the target’s “ringing,” excited by impulse illumination (Moser et al., 1983).

• 2 Picosecond range. Freely propagating beams of single-cycle picosecond waveforms can provide a potential communication channel. These signals can be generated by high-speed photoconductive switches (Auston et al., 1984), short-lived electric dipoles (Krokel et al., 1989), or frequency-independent optoelectronically pulsed spiral or horn antennas (Pastol et al., 1990). Moreover, such transients are finding steadily increasing applications in microwave transient spectroscopy and millimeter wave generation (Lutz et al., 1989).