ECE Research Seminar: Designing the Phase Locked Loop FM Stereo Demodulator

Abstract

During the second and third summer of my graduate electrical engineering studies at Illinois Institute of Technology, I worked in the small research department of Warwick Electronics in Niles, Illinois, then one of the largest manufacturers of consumer electronics in the world. My supervisor, William Padgett, was interested in applications of the phase locked loop (PLL) in FM radio design, and he asked me to investigate applying a PLL to the recovery of the stereo subcarrier in a FM stereo demodulator. This work resulted in a published paper, a patented design, and, shortly thereafter, the first PLL-based FM Stereo Demodulator integrated circuit that has been used in almost every FM stereo radio produced since 1971. This presentation describes the FM stereo composite audio signal, historically how it is generated and demodulated, the problems encountered using a PLL to synchronize the 38 kHz subcarrier, the underlying mechanisms causing the problems, and their solutions. This shows that it is possible that an engineering student can do important work while an intern.

Biography

Jeffrey N. Denenberg has more than 30 years of experience in the electronics, communications, and computer industries. He has also been active in engineering education, teaching graduate and undergraduate engineering and computer science courses at several schools (including five years at Illinois Tech before relocating to New England) and at Fairfield University for more than 25 years. He received his B.S. in electrical engineering from Northwestern University in 1966 and an M.S. in electrical engineering and a Ph.D. in electrical engineering from Illinois Tech in 1968 and 1970, respectively. Denenberg holds 20 patents covering a wide variety of technical areas. Most of his inventions have been used in commercial products. Denenberg has published many technical papers and has been a contributing author for two books. He is a senior life member of the Institute of Electrical and Electronics Engineering, has been awarded the ITT Corporation Inventor of the Year, and is a BEI Fellow of the School of Engineering at Fairfield University.