Arbitrary ADC resolution at the receiver

Hello everyone,

I excuse myself on advance by my noob question…

I have an N210 with an SBX front end, and I want to experiment with
decoding signals at a lower resolution, rather than the default 12 bits
provided by the N210 ADCs. Does anyone know if (and how) can I limit the
resolution of the ADCs arbitrarily?

I am aware that I can reduce the resolution afterwards, mapping the
signals
to a lower resolution in base band, but I’d really like to do that
before
the DDC at the FPGA.

Cheers to everyone!

Leonardo S. Cardoso
[email protected]


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The n200 and n210 have 14 bit ADCs.

In any case, you can fake fewer bits by zeroing the low order bits in
the
fpga.

Matt

Yes, 14 bits… mistyped the ADC resolution…

Thanks, Matt. I’ll investigate this idea…

Leonardo S. Cardoso
[email protected]

Hi Marcus,

There are several reasons why we would like to avoid reducing the
resolution in software: 1. Reduce receiver complexity; 2. Capture any
artifact of the DDC with respect to the reduction of the resolution.

Frankly speaking, I’m not sure any of these arguments are defendable to
impose a resolution control at the ADC or even the ADC-FPGA interface.
If
it isn’t, then I agree it is much simple to do it in soft.

BR,

Leo

Leonardo S. Cardoso
[email protected]

On Mon, Jun 30, 2014 at 5:46 PM, Marcus Müller
[email protected]

Hi Leo,

well, I’d argue that reducing receiver complexity doesn’t really happen
when you start changing the FPGA with respect to dev effort; I can see
your DDC numerical accuracy point, though.
However, how would reducing the ADC resolution make artifacts more
noticable? As you get ca -6dB theoretical SNR with each bit you cut at
the ADC, errors in the DDC should become less relevant, not more.

Best Regards,
Marcus

Just out of curiosity: Why would you want to reduce the ADC resolution?
Most of the effects introduced can be simulated in GNU Radio, e.g. by
converting a float stream to integer and dividing it by a constant power
of two.

Greetings,
Marcus

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