Hi. I'm doing initial verification of a B200. A sine wave at 100MHz is fed into front end. The receiver is configured to use its quadrature downconverter to bring the wave down to 100kHz, which is then sampled by a GR "USRP Source" component and displayed in a "Frequency Sink" GUI. I notice the following unexplained behavior: as long as I set the Sampling Rate parameter of the radio to anything > or equal to 200 kHz (i.e. more than twice the frequency of the analog tone I'm trying to sample) I see the tone in the FFT output where I expect it to be; however, any sampling frequency less than that, and I get no output at all. For example, with the 100kHz tone in my experiment, setting the sampling rate to 100kHz should result in a spectral line near DC, however, no output is observed. It is almost as if there is something going on behind the scenes that doesn't allow for aliasing to happen, either in the stock FPGA design or some other block external to the FPGA. Can anyone comment? I just want to conduct a very basic sanity check of the received down-conversion and sampling. Is there a functional description of the digital and analog processing chain that B200 comes from the factory with? Thanks
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