Mixer Vref and sin wave

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alma_284856
Level 3
Level 3
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Hi everyone,

I am struggling using the Mixer correctly.

My goal is to mix a sin Wave (Fin =À low freq 10Hz) with carrier frequency 20kHz (LO internal) and get an output amplitude of around 2Vpp.

overall.png

I have with me an old freesoc mini with a 5LP CY8C5868LTI-LP039 (VDD=3.3V).

I used a WaveDAC, set my range to 4.080V, put an offset at 1.024V to be able to get something around 2Vpp

DAC.png

The mixer is configured as below: Multiply up, internal LO 20Khz

mix.png

I would have thought to get something like this:

wish.png

But I can't get anything nice.

First of all, my sinus has a lot of ripple at the frequency of the carrier.

Then my output is centered at 1.024V but the amplitude is not constant:

output.png

I could not find anything about the mixer that is not out of date like this https://www.cypress.com/documentation/code-examples/ce95337-analog-signal-mixer-psoc-35lp

Do you have any idea where the problem could be? When the mixer multiply by +1 or -1 it need to have the Vref plus also the top Vmax and Vmin of the Fin no?

Thank you all.

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1 Solution
Vasanth
Moderator
Moderator
Moderator
250 sign-ins 500 solutions authored First question asked

Hi,

I could recreate the issue at my end. I resolved the issue by buffering the WaveDAC output as shown below. Resultant waveforms are also provided below.

Circuit modification:

pastedImage_0.png

Resultant Waveform after modification:

pastedImage_1.png

Best Regards,
Vasanth

View solution in original post

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3 Replies
Vasanth
Moderator
Moderator
Moderator
250 sign-ins 500 solutions authored First question asked

Hi,

I could recreate the issue at my end. I resolved the issue by buffering the WaveDAC output as shown below. Resultant waveforms are also provided below.

Circuit modification:

pastedImage_0.png

Resultant Waveform after modification:

pastedImage_1.png

Best Regards,
Vasanth

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Vasanth,

Isn't

pastedImage_0.png

the same this as:

pastedImage_1.png

???

Len

Len
"Engineering is an Art. The Art of Compromise."
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Hi Len,

Yes, both are the same. We can use VDAC 0 -4.080 (Buffered) in the range selection to enable buffering internal to the component.

Best Regards,
Vasanth

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