Quote : "Who would have expected an unterminated HCMOS gate to be able to emit 2W at 200MHz?"
Not me - 2 Watts of effective radiated power implies over 2.5 V/m at 3 m! I guess I have a hard time believing that was transmitted from an HCMOS gate. I think a little common sense will go a long way towards retiring some of these EMC-urban legends. on 1/6/02 10:40 AM, cherryclo...@aol.com at cherryclo...@aol.com wrote: A.2) A portable computing device used in an automatic change machine on board transport was tested to be fully compliant with EN 55022 (approx = CISPR 22). I helped the manufacturer investigate complaints of interference and discovered that sub-fitted variant, which had not been tested for EMC compliance, left an HCMOS inverter IC with an unterminated inverter - which promptly decided to self-oscillate at 200MHz. (Many manufacturers of products with a number of build variants only test the fully-loaded one for EMCD compliance and assume the others are at least as good.) The very interesting thing about this example is that the power-ground structure of the PCB made a beautifully tuned antenna and resonant circuit at 200MHz, so although the inverter was hard-switching and did not run hot, the only emissions were at the 200MHz fundamental - no harmonics were emitted at all. Another very interesting thing is that some of the complainants had measured the equivalent radiated RF power from these devices as 2W. Who would have expected an unterminated HCMOS gate to be able to emit 2W at 200MHz?
