Timed Arrays

1TIMED AND PHASED ARRAY ANTENNAS

This chapter briefly introduces antenna arrays and the difference between phased and timed arrays. Not long after the invention of antenna arrays, researchers experimented with moving the main beam by modifying the phase of the signals fed at the elements [1]. Manual beamsteering eventually led to the invention of the phased array where the main beam was electronically steered to a desired direction by applying a pre-calculated phase to all the elements [2]. Phase is a narrow band concept, though. Today’s applications of antenna arrays require high data rates and wide bandwidths. The term “timed arrays” applies to several classes of antenna arrays that are becoming more important with the development of new technologies that must be designed, analyzed, and tested in the time domain, rather than the steady-state, time harmonic forms used with phased arrays. One author defined timed arrays as [3]“…timed-domain equivalent of phased arrays, where each radiating element is excited by pulsed instead of narrowband signals.” This book adds adaptive arrays, reconfigurable arrays, and other time-dependent arrays to that definition of timed arrays.

1.1 LARGE ANTENNAS

Large antennas collect more electromagnetic radiation than small antennas. They have the potential to detect very faint signals—the reason they are popular for radio astronomy and radar. Consequently, an antenna has gain that magnifies the received or transmitted signal in the direction ...