Peltz oscillator with injection locking
Oscillator injection locking is an attention-grabbing topic; nevertheless, it appears to be a forgotten circuit idea that may be useful in some purposes.
Wow the engineering world along with your distinctive design: Design Concepts Submission Information
This design thought reveals an software of the built-in Bode functionality inside many trendy 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 gadget below 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 working 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 working oscillator frequency of ~75.5 kHz.
Evaluation and measurements
As proven in Determine 2, the evaluation from Razavi [2] reveals the injection locking vary (± Δfo) across the free working oscillator frequency fo. Be aware 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 working oscillator frequency fo.
This evaluation predicts a complete injecting locking vary of two*Δfo, or 2.7 kHz, which agrees properly 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 reveals 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.
Be aware the measured outcomes present a section reversal as in comparison with the illustration notes (Determine 2) and the Razavi [2] article. This was because of the creator not defining the preliminary section setup (180o reversed) in settlement with the article and finishing the measurements earlier than realizing such!!
Injection locking use case
Injection locking is an attention-grabbing topic with some makes use of even in at the moment’s trendy circuitry. For instance, I recall a reasonable arbitrary waveform generator (AWG) which had a comparatively giant frequency error because of the low-cost inside crystal oscillator utilized and needed the power to make use of a ten MHz GPS-disciplined sign supply to enhance the AWG waveform frequency accuracy. As an alternative 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 proper circuit location solved the issue with no single reduce to the PCB! The AWG would function usually with the interior crystal oscillator reference until 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” approach fixing a present-day downside!
Michael A Wyatt is a life member with IEEE and has continued to get pleasure from electronics ever since his childhood. Mike has a protracted profession spanning Honeywell, Northrop Grumman, Insyte/ITT/Exelis/Harris, ViaSat and retiring (semi) with Wyatt Labs. Throughout his profession he amassed 32 US Patents and previously printed a number of EDN Articles together with Greatest Thought of the 12 months in 1989.
References
- “EEVblog Electronics Neighborhood 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 Strong-State Circuits, vol. 39, no. 9, pp. 1415-1424, Sept. 2004, doi: 10.1109/JSSC.2004.831608.
- Wyatt, Mike. “Easy 5-Element Oscillator Works under 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 under 0.8V
- Injection-lock a Wien-bridge oscillator
- Extremely-low distortion oscillator, half 2: the actual deal
- The Colpitts oscillator
- Clapp versus Colpitts
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The put up Investigating injection locking with DSO Bode operate appeared first on EDN.
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