Do you have any detailed information (application note or any other documents) about tunable reference for HMC832?
We would like to know the detailed about tunable reference for HMC832.
Please see section 188.8.131.52 of the HMC830 Operating Guide for more information on operation with tunable reference. We can implement the algorithm either as a look up table or compiled Matlab code for your controller. The algorithm simply predicts the location of spurs and adjusts the reference frequency accordingly to move the spur outside the loop filter bandwidth.
Many thanks for your answer.
When any integer boundary spur occuer at 1st PLL, do those spurs have some effect on the output of 2nd PLL?
Or do those spurs reject in the 2nd PLL?
The second PLL loop filter will attenuate spurs from the 1st PLL but only if they fall outside the loop bandwidth of the 2nd PLL . For example if the 1st PLL spurs are located at 10KHz offset then the second PLL loop filter must be set to something less than 10KHZ to have any effect.
There is however a trade-off. By setting the 2nd PLL loop to such a low value this increases the VCO phase noise contribution out of the 2nd PLL. You get some reference spur attenuation but overall the phase noise may be higher than for a wider loop. Ideally set the 1st PLL to use integer mode, which removes any integer boundary spurs, and optimize the 2nd PLL loop filter for best phase noise.
Many thanks, Dean-san.
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