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ADF4355 output spurious components

Question asked by mmilosavljevic on Oct 29, 2017
Latest reply on Mar 1, 2018 by MaYongfeng

Dear Support Team,

 

Please see attached the spectrum from the ADF4355 that I get for the frequency range between 6.2GHz-6.6GHz (this example is the 6.4GHz). I havent tried frequencies outside this range as they are not needed for my application and the filters on a board wont allow me anyway. 

 

My question is whether this the best I could get in terms of those spurious components that are about -35dBm down from the carrier (the one with the D1 marker)? I tried adjusting several parameters of the PLL but didnt see any difference in the frequency response. For example the device tree properties for the device when i was plotting this were (the reference frequency is 40MHz):

 

adf4355-rx-lpc@0 {

                              compatible = "adf4355-2";

                              reg = <0x0>;

                              spi-max-frequency = <10000000>;

                              clocks = <0x9 0x0>;

                              clock-names = "clkin";

                              adi,power-up-frequency = /bits/ 64 <6400000000>;

                              adi,charge-pump-current = <900>;

                              adi,muxout-select = <6>;

                              adi,charge-pump-negative-bleed-enable;

                              adi,mute-till-lock-enable;

                              adi,output-a-enable;

                              adi,output-a-power = <1>;

                        };

 

Do you have any suggestions for improvements or this is the best i can get? I am curious why are these components there?

 

Thanks

Milos

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