Johannes A. Greefkes

Biography

Johannes Anton Greefkes was born in Amsterdam in 1912. He attended public school in Amsterdam and took his first job as a power engineering supervisor with N.V. Vos and Sons. After five years with Vos, he joined the Telecommunications branch of Philips, Eindhoven, in 1938. He helped develop Philips' first carrier telephony system, which was installed between Sydney and Maitland, Australia. During the war years, he was engaged on several advanced developments: SSB radio relay links, echo suppressors, and carrier telephony, notably the successful modular 48-channel system known as the STR7, which was installed in the Netherlands in the late forties.

With Frank de Jager, he collaborated in the field of signal processing for speech transmission led, inter alia, to their joint receipt of the Veder Award in 1958 for their work on the narrow-band transmission of speech with low signal-to-noise ratios (Frena system). Their other joint work has included a valuable contribution to the invention of delta modulation and the development of a digitally controlled form of the latter (DCDM), a special feature of which is syllabically controlled compansion, and which was employed on an increasing scale.

Greefkes remained in charge of code modulation research at the Philips Labs until he reached the company's retirement age in 1982 and joined the staff of the Eindhoven Technological University.

Greefkes was a Fellow of the IEEE.