Dear sirs,

I am a new comer here. Recently I got a problem on the captioned on my job.

Our company designed a toy with micro-phone cable. We found that 352 & 388 MHz noise is strongly emitted out of the toy when we did outside lab FCC/EMC pre-scan. The pre-scan result varies from time to time as the orientation of the mic cable (like an antenna). It shows that the noise radiated out there. The cable is already sprially shielded. We test it without mic cable and got at least 11 dB safety margin.

There are 3 wires in the mic cable, namely mic signal, GND and control on/off (chip reset). 3 wires are connected to the voice chip with frequency changing feature. We tried to put 100pF, 220pF, 470 pF on the mic 5V supply line and/or chip's AVcc & DVcc with 220pF but no luck. Tried to put a ferrite bead in series with the mic signal, still no luck.

Now hope anyone here could advise me some ideas to resolve this problem.

Best Regards,
Nelson
hk_jedi@yahoo.com