Substrate Noise Coupling through Planar Spiral Inductor

While previous studies on substrate coupling focused mostly on noise induced through drain-bulk capacitance, substrate coupling from planar spinal inductors at radio frequency (RF) via the oxide capadtance bas not been reported. This paper presents the experimental and simulation results of substrate noise induced through planar inductors. Experimental and simulation results reveal that isolation between inductor and noise sensor is less than -30 dB at 1 GRz. Sepantion by distance reduees coupling by less than 2 dB in most practical cases. Practical examples reveal an obstacle in integrating RF tunedgain amplifier with sensitive RF recelver circuits on the same die. Simulation results indicate that hollow inducton have advantages not only in having a higher self-resonant frequency, but also in reducing substrate noise as compared to conventional inductors. The effectiveness of using broken guard ring in reducing inductor induced substrate noise is also examined.