ADAU1701 Lock-in amplifier

karolina_1 on Sep 17, 2018

Hi,

I would like to design a "Lock-in amplifier" using ADAU1701 DSP chip. Lock-in uses a technique known as phase sensitive detection to single out the component of the signal at a specific frequency. Signals at other frequencies are rejected through software (DSP lock-in) filtering. Would it be possible to design a lock-in amplifier using ADAU170?

I was thinking to use ADAU1701 DSP chip, with SigmaStudio graphical development tool in order to design Lock-in amplifier as shown in the figure. I added noise, to the input signal of interest(500Hz), the reference signal is also 500 Hz, two multipliers have been used as mixers for IQ demodulation(after multiplication of signals, we should get DC(0Hz) signal and 1000Hz signal because its output will be two signals with f1-f2 and f1+f2 frequencies), Hilbert transform was used to the output signal and its 90 phase shifted version. After demodulation, it goes through the filter in order to filter out 2f frequency and etc.

I was thinking to buy EVAL-ADAU1701MINIZ, together with USBi control interface board. If there is a better alternative, I would be glad to know.

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amiclaus
Dec 20, 2018 +1 verified
Hello,

For more information about the usage alternatives of this audio processor please post your question to the appropriate section: https://ez.analog.com/audio/

Thank you,

Antoniu

+1 amiclaus

on Dec 20, 2018 4:21 PM
Hello,

For more information about the usage alternatives of this audio processor please post your question to the appropriate section: https://ez.analog.com/audio/

Thank you,

Antoniu
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0 bestekemaloglu on Dec 2, 2021 12:22 PM

Hello there. I am Beste. I'm a university student. Is there any other function that we can use to get phase in lock-in circuit other than hilbert transform? Also, apart from this circuit, can we draw a lock-in circuit using different elements?Thank you from now. Have a good day.
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0 mthoren_adi

on Dec 4, 2021 4:18 PM in reply to bestekemaloglu
Hi Beste,

What hardware / software are you using in your lock-in circuit?

It looks like the Hilbert was used above in SigmaStudio because the signal generator did not have quadrature outputs (sine / cosine.) If you are using SigmaStudio and the ADAU1701 specifically, you might ask in:

https://ez.analog.com/dsp/sigmadsp/

If you're looking for general information on lock-in techniques, do a web search on "lock-in detection", there are lots of application notes.

This is an old thread, if you have any follow-on questions, please start a new one and refer back to this one if you want.

-Mark
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0 bestekemaloglu on Dec 6, 2021 11:04 AM in reply to mthoren_adi

Thank you Mark. If I have any other questions, I will ask.
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0 bestekemaloglu on Dec 15, 2021 5:15 AM in reply to mthoren_adi

Hello Mark. The circuit I built and the output I got are as in the image. I am using the Adau1701 board. When the input signal and the reference signal have the same frequency value, we need to obtain a flat signal. I cannot see such a signal on the oscilloscope when I equalize it. What should I do for it?
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