Last week, We did our first round of EMC test for Muno. Since Muno is a wireless consumer device, we need to make sure its radio frequency performance and electrical safety meet the regulation specifications.
The EMI test was done in an anechoic chamber, it is so quiet that people could get mad if staying inside it for 10 minutes. The test runs radio frequency from 30MHz to 1GHz. It follows specification “EN 55022: 2010/CISPR 22:2008 Class B”. And our result is PASS. So happy to know that at the worst frequency 405.31MHz, Muno still has -7.97dB margin against the spec.
On the ESD test, Muno does not perform well. We failed. We are targeting an air discharge of 8kV with B class performance, which means the device could reset but should be auto-recovery. But Muno could not pass it at several sensitive points, for example the speaker.
At the lab, we analyzed that the ESD failure is mainly caused by the capacitive touch module at the top side of Muno wooden box. The piece of circuit we did not design well: the grounding is week. In order to achieve high sensitivity (against the 4mm thickness wood surface), we tuned the circuit to be very sensitive. We now have a plan to re-design this circuit to balance the sensitivity and ESD safety. A better grounding design is necessary. Once we finish, we will come back to test again.
Very much appreciate our old friend Bill and Mary at the EMC lab who helped us defining the test strategy, doing the test and analyzing the results. We are pretty confident Muno could pass all of them and finally got FCC/CE certifications. Thanks a lot and enjoy music!