300 GHz path loss measurements on a computer motherboard

This paper presents the 300 GHz path loss measurements on a computer motherboard. In the measurement campaign, three different scenarios have been considered: a line-of-sight (LoS) scenario in the presence of a large ground plane (i.e. motherboard), a LoS scenario where the transmitter (Tx) and receiver (Rx) have different heights such as a link between the processor and memory, and an obstructed LoS scenario where the EM waves are guided from the Tx to the Rx through the metal parallel-plate structures such as Dual In-line Memory Modules (DIMM's) on the motherboard. The results show that in the presence of the motherboard, LoS path can be positively or negatively interfered by the reflections from the ground plane. The outcome strongly depends on the antenna position with respect to the motherboard. Furthermore, it is found that if the Tx and Rx antennas are not on the same height, the height difference of less than a centimeter between antennas is tolerable. However, the height difference of several centimeters, as found in links between the processor and memory would suffer from significant path loss. Finally, it was found that the chip-to-chip link that is obstructed by a parallel metal plates can experience both path loss higher or lower than free space path loss, depending on the spacing between metal plates. All these results indicate that optimal communications can be achieved by carefully positioning the antennas with respect to the motherboard layout.