Noise coupling to on-chip integrated antennas

Noise from digital circuits can couple to on-chip integrated antennas and degrade the received signal-to-noise ratio. To investigate coupling mechanisms, integrated antennas and noise generating circuits were fabricated in 0.25 μm and 0.1 μm CMOS processes. Noise coupling through the substrate is found to be common-mode in nature. Signals on long interconnects near antennas, as well as time-varying signals on V_DD and ground lines from switching action, are found to capacitively couple to antennas. Loss and phase delay in the transmission line cause this coupling to appear differentially. Less noise is found to couple in balanced measurements. This suggests that by using integrated antennas with a balanced feed structure, noise coupling can be reduced.