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# PSoC 5, 3 & 1 MCU

New Contributor II

## Downmixing above 4 MHz with PSoC 5LP

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Dear Cypress Community,

I am using an evaluation board for PSoC 5LP (CY8CKIT-059) and trying to downmix a signal.

My aim is to downmix a noisy signal that contains a very small sine wave (1mVpp) whose frequency is known, e.g., 10 MHz. The DC value I would get after the mixing+filtering tells me if that sinewave is present in the signal or not.

I was able to achieve this only for sine waves of max. 4 MHz using the mixer component of 5LP.

Question: Is it possible to mix with a frequency higher than 4 MHz so that I can downmix a 10 or 15 MHz signal?

I ask this because I do not want to include/pay a separate (I-Q) demodulator in my design.

Cheers,

Matija.

1 Solution
Honored Contributor II

## Re: Downmixing above 4 MHz with PSoC 5LP

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Technically, PSoC5 doesn't have analog capability in 10-15MHz frequency range.

I suggest using a simple Tayloe mixer to downsample incoming sine signal. See, for example this YouTube video (closer to the end)

https://youtu.be/JuuKF1RFvBM

There are many other links for Tayloe detector schematic. See.e.g:

http://www.norcalqrp.org/files/Tayloe_mixer_x3a.pdf

https://www.arrl.org/files/file/Technology/tis/info/pdf/020708qex013.pdf

Basically, it is 4x fast analog switch, which is controlled by a pair of quadrature signals I and Q. The output is practically a DC voltage and can be amplified by slow opamps in psoc. Knowing the amplitudes of the quadrature signals, one can calculate the phase of the incoming sine signal.

The analog switch is cheap (\$1). So all it needs is to generate a pair of digital quadrature signals I and Q at 10MHz, alongside with the source sine.

If the phase of the incoming signal is fixed (for example it is being provided by local signal generator), then Tayloe mixer simplifies even further, as Q component is not needed, and 4xF frequency generator is not needed, etc.

Here is another good link with PSoC5 project using Tayloe mixer by Mike Hightower (attached)

0-500khz Very Low Frequency direct sampling SDR

Can you provide more specifics on the project to help you better?

/odissey1

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