EMC and RFI problems and solutions on the SUNSAT micro-satellite

The 63 kg SUNSAT micro-satellite includes VHF (144-146 MHz) narrowband FM (NBFM) radio receivers for amateur radio service. Significant radio frequency interference (RFI) from data buses was a problem, but was successfully screened from antennas using aluminium plates. The harmonics and noise of from the 650 kHz switching regulators drifted through receiver channels causing unpredictable sensitivity losses of up to 20 dB. Without shielding, the regulators generated signals at VHF of -85 dBm in a quarter wave antenna at 0.5 m range. This is 34 dB above the noise floor of a 2 dB NF 18 kHz BW VHF receiver. Test results, solution methods, measurement techniques, and lessons learned are reported in this paper.