[Amps] Cell phones, digital cameras and RF

[Jim Brown]

On 3/5/2012 9:40 AM, Fuqua, Bill L wrote:
> 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