Several DDS parts from Analog Devices (e.g. AD9854, which runs quite warm) are dual quadrature.. And have adjustable phase offsets as well. I think the single DDS parts also have a programmable phase offset of 14-16 bits. You have to be careful with the configuration bits, so that writing the phase register doesn't zero the phase accumulator.
They're all available as eval boards, too. > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Hal Murray > Sent: Tuesday, December 23, 2008 10:59 AM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] New topics (was Re: He is a Time-Nut > Troublemaker....) > > > > 2. Several measurement techniques require a given phase > relationship > > (e.g., quadrature) between DUT and reference. For HF > frequencies (ie, > > 5 or 10 MHz) is there a *practical* phase shifter design covering > > 180+ degrees that doesn't involve switching various lengths of coax > > in and out of the line? > > PLL up by a factor of N, use that to drive a DDS, then > filter. Maybe a pair of DDSes will get better tracking. > > For each possible phase offset, you need N slots in the > table. (N/4 with more work) _______________________________________________ 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.
