Hi John, we have a new 100MHz board (FireFly-IIA-100MHz) that uses an ADF4002 to generate 100MHz from the 10MHz internal OCXO. The VCXO we use is rated at better than 100dBc at 100Hz. The 10MHz reference achieves typ. -148 dBc at 100Hz. We measured -115dBc/Hz at 100MHz at 100Hz offset in a couple of sample units using the TSC5125A. This is in-line with your measurement at 80MHz. Loop BW is ~30Hz, so the 100Hz offset is slightly outside of the ADF4002 loop BW. Note that we get ~15dB better performance at 100Hz offset than the VCXO datasheet would let us expect. bye, Said In a message dated 3/9/2010 14:00:16 Pacific Standard Time, [email protected] writes:
I haven't exhaustively tested the ADF4107 but I have played with the ADF4002 recently. I haven't been able to come within several dBc/Hz of its rated noise level. In one test, at 100 Hz from an 80 MHz carrier, I've seen about -118 dBc/Hz from the ADF4002 when fed by 10 MHz with -145 dBc/Hz at 100 Hz (which would become about -127 dBc/Hz in an ideal 80 MHz multiplier.) The figure-of-merit equation suggests that -222 + 20*log(8) + 10*log(10 MHz) = -134 dBc/Hz would be achievable, well below the -127 dBc/Hz limit imposed by the reference. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
