>> They must be very well shielded!
>>
> They are operating at VERY widely separated frequencies, AND their
> circuit board layouts must be carefully done to avoid both radiation and
> reception. I would bet that most modern products use multi-layer boards
> with ground layers to create microstrip and/or stripline techniques. By
> doing so, every circuit trace becomes a transmission line, with return
> current flowing on the ground layer below the trace. The primary reason
> for doing this is to minimize crosstalk between circuitry within the
> device, but it also serves to kill antenna action on those traces.
>
> There's an excellent discussion of this in Henry Ott's classic text on
> EMC.
>
> 73, Jim Brown K9YC
Another reason for reduced susceptibility by handheld devices like phones to
RF in general is the electronics are so highly integrated that what used to
take inches of traces between multiple chips is now an internal IC
connection of a few mm, if that. And yes, with signal clock speeds so high,
designers and their tools are far more sensitive to trace-as-antenna and
trace-as-transmission line both from a performance and a compliance
perspective. In this case, increasing integration works in our favor :-)
73, Ward N0AX
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