Hi All, I don't have our own results in a handy packaged format, but this correlates well with what we saw. If the 533 MHz is fundamental, it is pure PowerPC - the clock is generated on chip from a lower frequency reference.
Regards, Francois On Tue, Sep 6, 2011 at 10:29 PM, John Ford <[email protected]> wrote: > > John, > > It's interesting that there is almost no evidence of the 500 MHz ADC > > clock, > > except perhaps the 2000 MHz tone. I guess that means the ADC clock > > transmission lines are well terminated and not radiating. Most of the > > lines > > look like they are related to the PPC (multiples of 33 MHz) and the 100 > > MHz > > system clock. > > You're right that most of this is due to the PPC and ancillary circuits. > I expect that it's because the FPGA is not loaded. The line from the > clock to the ADCs is very short. I am going to test it again later with > the FPGA running a spectrometer bof, and all the xaui cables connected and > passing data around. > > For now, this is enough to tell me that we need to be thinking ahead to > packaging VEGAS. > > John > > > Glenn > > > > On Tue, Sep 6, 2011 at 1:14 PM, John Ford <[email protected]> wrote: > > > >> Hi all. > >> > >> We tested a ROACH and and 2 ADC boards (3 GS/s boards) in our anechoic > >> chamber to get a feel for the emissions to expect from the new > >> spectrometer being designed. The ADC clock was running at 500 MHz. > >> > >> The results of the test are attached. In summary, to use these at our > >> site, we will have to have a supplementary shielded enclosure in > >> addition > >> to our shielded equipment room. > >> > >> Thanks to Carla Beaudet at NRAO for the testing. > >> > >> (If anyone has anything they'd like us to test in the chamber, let me > >> know.) > >> > >> John > > > > > > -- Francois Kapp Sub-system Manager Digital Back End meerKAT SKA South Africa Third Floor The Park Park Road (off Alexandra Road) Pinelands 7405 Western Cape South Africa Latitude: -33.94329 (South); Longitude: 18.48945 (East). (p) +27 (0)21 506 7300 (p) +27 (0)21 506 7360 (direct) (f) +27 (0)21 506 7375 (m) +27 (0)82 787 8407
