Floyd M. Gardner


Floyd M. Gardner is well-known expert and author in the area of PLL's. The first, second, and third editions of his book Phaselock Techniques have been highly influential and remains a well-recognized reference among electrical engineers specializing in areas involving PLL's. In 1980, F. Gardner was elected IEEE Fellow "for contributions to the understanding and applications of phase lock loops".

Garner's conjecture on charge-pump phase-lock loops

He has written a remarkable IEEE paper dedicated to the description, the mathematical modelling and the characterization of the widely used Charge-Pump Phase-Lock Loops. This paper constitutes a major tutorial for scientists and designers who want to discover this very widely used mixed-signal system. In this paper Floyd M. Gardner derived a linear mathematical model of CP-PLL and, based on its analysis, conjectured that transient response of practical charge-pump PLL's can be expected to be nearly the same as the response of the equivalent classical PLL.

Gardner's problem on the lock-in range

Floyd M. Gardner introduced a lock-in range concept for PLLs and posed the problem on its formalization. In the 1st edition of his book he introduced a lock-in frequency concept for the PLL in
the following way: If, for some reason, the frequency difference between input and VCO is less than the loop bandwidth, the loop will lock up almost instantaneously without slipping cycles. The maximum frequency difference for which this fast acquisition is possible is called the lock-in frequency. Later, in the 2nd and 3rd edition of his book, Gardner noted that despite its vague reality, lock-in range is a useful concept and there is no natural way to define exactly any unique lock-in frequency.

Some well-cited papers