Transceiver Toolkit Design Example

Hi Peter,

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I am interested in making a device that outputs multiple channels of test patterns over SMA (single-ended, into 50 Ohm loads) at 10 Gbps or faster.

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The code for generating arbitrary PRBS/LFSRs in parallel-mode in the fabric for being serialized in the transmitters is here:

http://www.ovro.caltech.edu/~dwh/correlator/pdf/lfsr_tutorial.pdf (http://www.ovro.caltech.edu/%7edwh/correlator/pdf/lfsr_tutorial.pdf)

http://www.ovro.caltech.edu/~dwh/correlator/pdf/lfsr_tutorial_src.zip (http://www.ovro.caltech.edu/%7edwh/correlator/pdf/lfsr_tutorial_src.zip)

I need to finish writing the transmitter section in the tutorial, however, the code is there.

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Since the dev board has 7x channels wired to SMA (7x transmit, 7x receive, all of them diff pairs), I think I should be able to make at least 6 channels output in sync. (The overall goal is to make a "poor man's 0 Gbps multichannel arbitrary pattern generator".)

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The Stratix V GX Development Kit might be a better option. Samtec have HSMC-to-SMA and PCIe-to-SMA breakout cables. Those cables let you access many more transceiver channels.

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What is your opinion on how likely I am to be able to get reasonable waveforms out of the SMAs if I terminate one of the differential outputs, and transmit only single-ended signals?

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I've done it before for LVDS, look at page 60:

http://www.ovro.caltech.edu/~dwh/carma_board/gda06rb004_carma_v0.87_dec03.pdf (http://www.ovro.caltech.edu/%7edwh/carma_board/gda06rb004_carma_v0.87_dec03.pdf)

Its not just a matter of simply terminating the signal with a resistor. You have to terminate it into the right kind of network. In the case of the network on p60, to the LVDS driver, it looks like a 100-Ohm load. To the RF input, it looks like a 50-ohm source. You can do the same for the transmitters.

Cheers,

Dave