Peltz oscillator with injection locking
Oscillator injection locking is an fascinating topic; nevertheless, it appears to be a forgotten circuit idea that may be useful in some purposes.
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This design thought exhibits an software of the built-in Bode functionality inside many fashionable low-cost DSOs such because the Siglent SDS814X HD utilizing the Peltz oscillator as a candidate for investigating injection locking [1], [2], [3].
Determine 1 illustrates the instrument setup and system beneath check (DUT) oscillator schematic with Q1 and Q2 as 2N3904s, L ~ 470 µH, C ~ 10 nF, Rb = 10K, Ri = 100K and Vbias = -1 VDC. This association and element values produce a free operating oscillator frequency of ~75.5 kHz
Determine 1 Mike Wyatt’s notes on producing a Peltz oscillator and injector locking setup the place the association and element values produce a free operating oscillator frequency of ~75.5 kHz.
Evaluation and measurements
As proven in Determine 2, the evaluation from Razavi [2] exhibits the injection locking vary (± Δfo) across the free operating oscillator frequency fo. Notice the locking vary is proportional to the injected present Ii. The element values proven mirror precise measurements from an LCR meter.
Determine 2 Mike Wyatt’s notes on the injection-locked Peltz oscillator displaying the injection locking vary across the free operating oscillator frequency fo.
This evaluation predicts a complete injecting locking vary of two*Δfo, or 2.7 kHz, which agrees nicely with the measured response as proven in Determine 3.
Determine 3 The measured response of the circuit proven in Determine 1 displaying an injection locking vary of roughly 2.7 kHz.
Growing the injection sign will increase the locking vary to three.7 kHz as predicted, and measurement exhibits 3.6 kHz as proven within the second plot in Determine 4.
Determine 4 The measured response of the circuit proven in Determine 1 the place growing the injection sign will increase the locking vary to three.7 kHz.
Notice the measured outcomes present a part reversal as in comparison with the illustration notes (Determine 2) and the Razavi [2] article. This was as a result of creator not defining the preliminary part setup (180o reversed) in settlement with the article and finishing the measurements earlier than realizing such!!
Injection locking use case
Injection locking is an fascinating topic with some makes use of even in at this time’s fashionable circuitry. For instance, I recall an affordable arbitrary waveform generator (AWG) which had a comparatively giant frequency error as a result of low-cost inside crystal oscillator utilized and wished the flexibility to make use of a ten MHz GPS-disciplined sign supply to enhance the AWG waveform frequency accuracy. As a substitute of getting to reconfigure the interior oscillator and butcher up the PCB, a easy collection RC from a repurposed rear AWG BNC connector to the best circuit location solved the issue with no single reduce to the PCB! The AWG would function usually with the interior crystal oscillator reference except an exterior reference sign was utilized, then the oscillator would injection lock to the exterior reference. This was computerized with out want for a change or setting a firmware parameter, easy “old fashioned” method fixing a present-day drawback!
Michael A Wyatt is a life member with IEEE and has continued to take pleasure in electronics ever since his childhood. Mike has an extended profession spanning Honeywell, Northrop Grumman, Insyte/ITT/Exelis/Harris, ViaSat and retiring (semi) with Wyatt Labs. Throughout his profession he collected 32 US Patents and previously revealed just a few EDN Articles together with Finest Concept of the 12 months in 1989.
References
- “EEVblog Electronics Group Discussion board.” Injection Locked Peltz Oscillator with Bode Evaluation, www.eevblog.com/discussion board/initiatives/injection-locked-peltz-oscillator-with-bode-analysis.
- B. Razavi, “A research of injection locking and pulling in oscillators,” in IEEE Journal of Stable-State Circuits, vol. 39, no. 9, pp. 1415-1424, Sept. 2004, doi: 10.1109/JSSC.2004.831608.
- Wyatt, Mike. “Easy 5-Part Oscillator Works beneath 0.8V.” EDN, 3 Feb. 2025, www.edn.com/simple-5-component-oscillator-works-below-0-8v/.
Associated Content material
- Easy 5-component oscillator works beneath 0.8V
- Injection-lock a Wien-bridge oscillator
- Extremely-low distortion oscillator, half 2: the true deal
- The Colpitts oscillator
- Clapp versus Colpitts
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