[time-nuts] FW: Injection locking

Murray Greenman Murray.Greenman at rakon.com
Tue Feb 2 20:04:40 UTC 2010

-----Original Message-----
From: Murray Greenman 
Sent: Wednesday, 3 February 2010 9:00 a.m.
To: 'time-nuts at febo.com'
Subject: Injection locking


Bruce's collection would be a good place to start. Thanks Bruce. Most of
the examples relate to microwave applications, where often there is no
alternative, but the approach works well on HF and VHF as well, and more
importantly, can be achieved with existing oscillators with little
modification. The IL technique works with ratios from 20:1 to 1:20 or
more, and works well with the GPSDO as a reference.

My experience is mostly with locking HF crystal oscillators. It works
with overtone as well as fundamental oscillators. With an overtone
oscillator you can couple into the mode suppression choke. With a tuned
tank Pierce oscillator you can couple into the output tank. With a
Colpitts, inject into the emitter, collector, or bottom of the crystal.
I have made an excellent 10MHz CMOS gate oscillator with 2MHz injection
into a varicap acting as one of the crystal load caps (output side).

Kit VK2LL and others have used 10MHz injection to lock the 20MHz
reference in common Icom HF transceivers.

Arguably the father of the Injection Locking technique would be Vasil
Uzunoglu, and I have some references for articles by him. The most
readable article is "Synchronous Oscillator outperforms the PLL" (from
EDN 1999) http://www.edn.com/contents/images/46326.pdf. It shows how to
emitter-lock a conventional Colpitts oscillator. The secret here is to
get the bias correct. The test and measurement techniques he uses are a
good way to assess performance. Robert Adler (inventor of the TV
remote!) also explored the IL technique.


US Patent 4,355,404 "Carrier Recovery Network for QPSK Modems employing
Synchronized Oscillators", Uzunoglu 1982
US Patent 6,580,330 "Injection Locked Oscillator Automatic Frequency
Centering method and Apparatus", Katznelson & Petrovic 2003 (has a good
list of background papers to read)
"A study of locking oscillators..." Proc IEEE R Adler 1973

That should keep you busy for a while!

Murray ZL1BPU

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