Antenna Arrays in the Time Domain: An introduction to timed arrays

The term phased array comes from the time-harmonic/steady-state analysis of antenna arrays. These arrays use phase shifters to electronically steer the main beam. Phase shifters cause beam squint and pulse dispersion for wide-band signals, so time-delay units are needed to correct these errors. Adaptive and reconfigurable arrays also have time-dependent responses. In addition, time-dependent spurious signals arise due to nonlinearities in amplifiers. This article presents several time-varying issues related to antenna arrays that should not be modeled by the time-harmonic representation of an array. Future antenna arrays will be wideband and time varying, so antenna arrays will have to be designed in the time domain.