Inventor of the Costas loop and Costas array
John Peter Costas received bachelor’s and master’s degrees in electrical engineering in 1944 and 1947, respectively. After obtaining a PhD from the Massachusetts Institute of Technology in 1951, Costas joined General Electric as an engineer. At GE, he developed a modified phased-locked loop that recovers the "suppressed" carrier in many digital communications receivers, known as the Costas loop. This invention had a profound effect on wireless receivers and modern digital communications. In the 1960s, Costas played a pivotal role in solving the mystery concerning the poor performance of sonar systems. He discovered that the rapidly time-varying channel made coherent processing inappropriate. His solution involved using a permutation array, now known as a Costas array, which possesses ideal properties to address the problem.