We challenge the perception that we live in a “proper world,” where complex random signals can always be assumed to be proper (also called circularly symmetric). Rather, we stress the fact that the analytic signal constructed from a nonstationary real signal is in general improper, which means that its complementary correlation function is nonzero. We explore the consequences of this finding in...

Article history: Available online 18 May 2012

Given a unitary operator A representing a physical quantity of interest, we employ concepts from group representation theory to define two natural signal energy densities for A. The first is invariant to A and proves useful when the effect of A is to be ignored; the second is covariant to A and measures the “A” content of signals. We also consider joint densities for multiple operators and, in ...

in this paper, a ground early warning receiver is introduced and explained for the reception and monitoring of signal from a space-borne synthetic aperture radar. this receiver can be used for various electronic warfare applications and implemented in two sectors of time parameter detector and frequency parameter detector. it can measure power, bandwidth, central frequency, pulse width, pulse r...