Analysis of on-chip digital noise coupling path for wireless communication IC test chip

In-band spurious tones of a LTE-class radio frequency integrated circuit (RFIC) receiver test element group (TEG) chip was studied in order to evaluate the degree of noise suppression by means of soft magnetic thin film. A 2-μm-thick crossed anisotropy multilayered Co-Zr-Nb film was applied onto the passivation layer of TEG chip. The in-band spurious was suppressed by 10 dB while it had no influence upon wanted signal. A magnetic near field map measured in the 2.1 GHz range indicated several noise coupling paths on chip, which were compared with the chip layout design to estimate victim wires. EM simulation model in connection with circuit simulation is carefully constructed. RF control wirings were most responsible wires than other wires and air couplings. EM simulation predicted the magnetic film should suppress noise by the maximum of 33 dB while it was 10 dB experimentally because of Si substrate coupling and board coupling.