John P. Costas (engineer)

John P. Costas (October 25, 1916 – December 29, 2011) was an American electrical engineer and professor known for his significant contributions to communications theory, particularly in the development of modulation and coding techniques. He is best known for his invention of Costas loops, a phase-locked loop circuit used for carrier synchronization in suppressed-carrier communication systems.

Costas earned his BSEE from the University of Rochester in 1937 and his MSEE and ScD degrees from the Massachusetts Institute of Technology (MIT) in 1939 and 1942, respectively. He worked for General Electric from 1942 to 1954, where he began his pioneering work on modulation theory. In 1954, he joined the MIT Lincoln Laboratory, where he continued his research and development efforts until 1967. He subsequently became a professor of electrical engineering at Syracuse University, a position he held until his retirement in 1987.

His invention, the Costas loop, enabled the demodulation of suppressed-carrier signals such as double-sideband suppressed-carrier (DSB-SC) and quadrature amplitude modulation (QAM) without the need for a pilot carrier signal. This advancement significantly improved spectral efficiency and signal integrity in communication systems.

Costas also made contributions to the understanding of frequency-shift keying (FSK) and other modulation schemes. His work laid the foundation for many modern digital communication systems. He was a Fellow of the IEEE (Institute of Electrical and Electronics Engineers) and received numerous awards and honors for his contributions to the field of communications engineering.