Dear EMC experts, Radiated Emission @ 72 MHz in horizontal polarization from the EUT is about 34 db microvolts measured at 3 meters. The EUT is a USB device connected to the USB port of the laptop computer through a 1-meter cable and the EUT is in 'USB Suspend' state. There is no switching (crystal is stopped, the processor is not executing any program code) current involved. The current consumed by the EUT is about 300 micro amps. Since I do not have a high precision current probe, I used 2 digital multi-meters one at the d.c +ve line & the other at the d.c. –ve line of the EUT to measure the current and the current is found to be exactly equal in magnitude in both the wires. Same EUT when directly connected to the laptop computer without the cable, the emission @ 72 MHz is below the floor level noise of the analyzer. Is it still a common mode problem?
Sincerely K.Balasubramanian Sr.Engineer, Hardware.
