FMC150 Filter Bypass

[evgenia89]

Hello,

I am using Virtex-6 DSP Development Kit with FMC150 DAC/ADC card.

I am wondering if there is a way to bypass internal high pass filters on the FMC150 card? I found two signs on the board: 'filter bypass', but there is no information how to use it.

I will appreciate any help!

Regards,

Evgenia.

[joelby]

Is the card made by 4DSP? You should probably contact them for support, since they don't seem to publish a schematic diagram.

The manual mentions filter bypass in the context of a DAC reconstruction filter only.

[evgenia89]

Yes, but in this case why did they put 'filter bypass' there?

If this is on the board, there should be a way to send signals to this route with vhdl code.

[joelby]

As I said, "filter bypass" seems to be for the DAC reconstruction filter:

"The AC coupled output uses wideband RF transformers (TC4-1W). An optional re-construction filter is available on each DAC output. Refer to Table 2 for the filter characteristics. The filter can be bypassed on the board with 0Ω resistors."

It's not possible to bypass this particular filter using VHDL since the switching mechanism involves fitting extra components to the PCB.

Why don't you want to use the high pass filter? Are you trying to sample down to DC?

[john_e]

You may want to try my workaround, which is a low IF upconverter into the DAC and a corresponding low IF downconverter after the ADC. You can easily adapt the upconverter and downconverter in Avnet's tutorial demo. The FMC150 is not designed for naked baseband work.