Floyd M. Gardner (1929 – 2021) was a well-known expert and author in the area of phase lock loops (PLLs).
The first, second, and third editions of his book Phaselock Techniques[1][2][3] have been highly influential and remain a well-recognized reference among electrical engineers specializing in areas involving PLLs.
In 1980, Gardner was elected IEEE Fellow "for contributions to the understanding and applications of phase lock loops.
[2]: 70 [3]: 187–188 A rigorous approach to solving the Gardner problem and exact analytical values for the lock-in range were suggested by N. Kuznetsov et al.[7][8][9] He wrote an IEEE paper[10] dedicated to the description, the mathematical modeling, and the characterization of the widely used Charge-Pump Phase-Locked Loops (see references below).
This paper constitutes a major tutorial for scientists and designers who want to discover this widely used mixed-signal system.