2.4GHz wake-up receiver with suppressed substrate noise coupling

The switching noise generated in digital circuits propagates through conductive silicon substrate to analog circuits in a mixed-signal CMOS LSI. Substrate noise coupling may degrade the performance of the analog circuits, and may result in a fault operation of the mixed-signal LSI in the worst-case. In this paper, the substrate noise coupling between the clock recovery circuit and the input port of the envelop detector in a low-power wake-up receiver (WuRx) was investigated experimentally. The propagation path of the substrate noise coupling was clarified by comparing the experimental results with the circuit simulations on the basis of an equivalent circuit model. The design of the WuRx was modified on the basis of the findings to suppress the substrate noise coupling. The fabricated WuRx successfully operated a 100-kbps PWM signal with a carrier frequency of 2.4GHz, and the effectiveness of the noise coupling suppression recipe was confirmed.