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Design >> RF Design >> how to distinguish frac spur and ref harmonic
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Message started by liliwang on Dec 26^th, 2004, 6:46pm

Title: how to distinguish frac spur and ref harmonic
Post by liliwang on Dec 26^th, 2004, 6:46pm

In a frac-N pll using 2rd orfer sigma-delta, when there is a strong spur neer carrier, how to distinguish it is a fractional spur or just reference harmonic.

What's the cause of reference harmonic, and how to reduce it.

Title: Re: how to distinguish frac spur and ref harmonic
Post by DaveB on Jan 5^th, 2005, 7:52pm

If it's at the reference frequency that's a strong hint. If you change channels and the spur stays at the same frequency offset, then it's likely a reference spur. If you change frequencies, and the spurious offset changes, then I'd suspect some sort of fractional spur.

Dave