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HMC832 integer boundary spurs

Question asked by cosmolittle on Nov 1, 2014
Latest reply on Nov 4, 2014 by DonY

Dear Sirs,

 

   I have a query about the HMC832 when used with the output frequency divider.

 

The data sheet gives graphs of phase noise when used with various divide values of the output divider. This shows the expected reduction in phase noise of 6dB with each divide by 2. What is the effect of the output divider on the integer boundary spurs? For a perfect divider I would expect the spur level to be reduced by 6dB for each divide by 2, and the offset frequency of the spurs to be unchanged.

 

  My question is relevant as I have been evaluating a competing device with a similar output divider. The use of the output divider introduces new integer boundary spurs at 1/N the spacing of the original spurs, where N is the divide value. These are at quite high levels.

 

An example:  VCO on 2000.05MHz, divider not used, int boundary spurs at +/-50kHz, level -28dBc

 

                    VCO on 2000.05MHz, divide by 2, output at 1000.025MHz, int boundary spurs at +/-25kHz, level -17dBc

                                                                                                             int boundary spurs at +/-50kHz, level -27dBc

Is this effect present in the HMC832?

 

I have not yet purchased the evaluation board, but intend to do so.

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