Franks L. Signal theory 2ed 1981

Textbook in PDF format

The book was a great help when I was in grad school and when I was involved with technical work on signal analysis and synchronization circuits for communication systems. Proakis's bible (Digital Communication) touches on this in his chapter on signal characterization, Franks goes more in depth. Signal theory was cutting edge back in the day, presently they have been disseminated into other books and consider legacy topics. Using vector spaces, norm and inner product was not talked about in earlier books on Signal Detection (see Whalen's classic work) now they are standard intro sections for detection and estimation theory. Cyclostationary processes was introduced, later his PhD student wrote a book on this class of signals. The sections on representing bandpass signals and systems is still relevant today and unfortunately lost to some engineers working in the field