Professor James Spilker: 1933-2019
James Spilker gained a degree, Masters and PhD in electrical engineering from Stanford University (1955-58). He joined the Lockheed Research Labs and during the 1960s wrote a number of papers on signal timing technology. These made the precision tracking of satellites, which is necessary for GPS, possible. He then worked for Ford Aerospace where he designed and implemented the payload for the world’s first military satellite communications system. Bradford Parkinson asked him to join him at Stanford in the 1970s, where Spilker contributed to the original GPS architecture and designed the GPS civil signal (L1 c/A code).
In 1973 Spilker co-founded Stanford Telecommunications Inc., which was selected by Parkinson to recommend the GPS signal structure for CDMA (code division multiple access). This was accepted by the US Air Force and became the civilian signal that is now used by 4 billion receivers. Spilker’s delay lock loop process for tracking CDMA signals was the key component that enabled the system and is essential to GPS accuracy. His team also developed and built the receiver that processed the first GPS satellite systems and operated a special on-orbit GPS satellite receiver that demodulates millions of signal bits to verify operation in the radiation belts.
Stanford Telecommunications Inc. was successfully sold in 1999, allowing Spilker to return to Stanford University to share with students, faculty and the world his professional knowledge and entrepreneurial experiences and further the progress of GPS and PNT.
Between 2001-05 he was an adjunct professor of engineering at Stanford University. In 2005, he co-founded the Stanford University Center for Position, Navigation and Time, and became the co-founder and executive chairman of AOSense Corporation in 2006. He was a lead designer in developing the L5 civilian signal, first launched in 2011. This provides higher accuracy and is more resistant to interference from space weather. He co-invented the split spectrum mode (binary offset carrier or BOC) that allows civilian and military signals to use separate areas of the spectrum. He also developed adaptive vector tracking for simultaneously tracking ranging signals from multiple satellites. This system maintains accuracy and has an improved performance against interference.
Vector tracking will be critical to handling GPS satellite navigation expansion in the future. Spilker won the AIAA Sommerfield Book Award for Global Positioning System: Theory and Applications (1996), considered the standard reference for GPS. His recognitions include the Kepler Award (1999) and the IEEE Thomas Edison Medal (2015).