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Injection locking: Where Christiaan Huygens meets the modern world...


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I designed the synthesizer and VCO for the DSP on an integrated circuits used in disk drives (circa 1995).  These designs went into WD, Seagate, and Quantum disk drives.  The VCO was slaved to the synthesizer (which was slaved to a crystal oscillator) and was designed to be adjusted according to where the read head was on the rotating disk (inside radius slower than when at the outside edge of the disk).

What we discovered was that as you dial the VCO near the frequency of the synthesizer, it just locked in and would not budge until you pushed it well past the reference frequency given by the synthesizer.  Wow...we were scratching our heads.  Somebody on the team discovered that we were not the first do notice this issue.

Christiaan Huygens also discovered that when clocks mounted on the same beam while closely regulated, will synchronize themselves.  In modern times, we call this "injection locking."

This bit of insight was exciting for me...being the son of a watchmaker.

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5 hours ago, LittleWatchShop said:

never made it work.

First of all you need a medium that transmits resonance. The UCLA video cheats hugely with the board sliding in the same vector plane as the metronome pendulums. 

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