Near Field Measurements of Sub-millimeter-wave Noise Emission from Digital Integrated Circuits

The 5
^th
generation (5G) communication system exploits millimeter-wave (mm-wave) frequency bands for high-speed and large-capacity cellular networks. Sub-mm-wave communication is severely challenged by the large path loss as well as the cable loss for attaining the certified performance level among receiver (Rx) and transmitter (Tx) chains, in comparison to sub-6 GHz counterparts. In addition, digital integrated circuits (ICs) for baseband functionality typically operate at the clock frequency in the order of GHz and emanate electromagnetic (EM) noises in a very wide range of frequency, which can impair 5G performance in a sub-mm-wave band. This paper exhibits the presence of high-order harmonics of digital switching noises from 22 GHz to 30 GHz. The near-field EM noise measurements using a sub-mm-wave down converter demonstrate the fact where the emission noise from digital ICs clocked at 1 GHz potentially becomes the root cause of EM interference in a cellular system using 30 GHz or even higher.