maniana
Member level 4
I have designed a board with a microcontroller (FX2) and 1.8GHz receive chain (LNA, I/Q downconverter, PLL, IF amplifier).
I was trying to follow all the guidelines for low EMI radiation but still I get a lot of noise at the output of my receiver, which I identified as coming from microcontroller. This noise is largely reduced when I touch with a finger the leads of a 24MHz crystal that is a clock for the microcontroller. As I said I payed a lot of attention to PCB design, so ground is well routed, power supply separate for uC and RF , there is a ground ring around that crystal oscillator, The separation between uC and Rf is about 10cm, etc...
Still, At some frequencies I get spurs in the receive spectrum spaced at 1kHz over several MHz.
I am generally an RF eng. and only occasionally deal with uC,
but how **** do I get rid of that noise from the microcontroller in my RF part ????
I was trying to follow all the guidelines for low EMI radiation but still I get a lot of noise at the output of my receiver, which I identified as coming from microcontroller. This noise is largely reduced when I touch with a finger the leads of a 24MHz crystal that is a clock for the microcontroller. As I said I payed a lot of attention to PCB design, so ground is well routed, power supply separate for uC and RF , there is a ground ring around that crystal oscillator, The separation between uC and Rf is about 10cm, etc...
Still, At some frequencies I get spurs in the receive spectrum spaced at 1kHz over several MHz.
I am generally an RF eng. and only occasionally deal with uC,
but how **** do I get rid of that noise from the microcontroller in my RF part ????