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I'm using the HMC832 in the conditions fixed in the datasheet p34 figure 52 (loop filter design).

We choose the loop filter type 1 in the table12. The Fxtal is 40Mhz.

I succeed in programming the module correctly and it is always locked.

But for some frequencies, it is not exactly locked at the right frequency.

For example, at 80Mhz the output is 81.5Mhz.

We use an Xtal=40Mhz and we noticed that it happened at 40/80/160Mhz.

Thanks for your help.



  • Hi Christine,

    1.5MHz offset on 80MHz sounds a lot. Are you able to lock a fractional frequency correctly, for example 80.1MHz or the other integer multiple frequencies? Did you disable the SD modulator (register 0x06 bit 11) for the integer multiple outputs?



  • The HMC832 is not programmed in integer mode (the fractionnal modulator is not disabled).

    The HMC832 is always locked but sometimes it is locked on a shifted frequency.

    We use an Xtal=40Mhz and we noticed that it happened at 40/80/160Mhz (and very probably on other frequencies).

    Otherwise, if I choose 80.1Mhz, the HMC832 is locked on the exact frequency.