A decreasing-sized pi-model electrostatic discharge (ESD) protection structure is presented and applied to protect against ESD stresses at the RF input pad of an ultra-low power CMOS front-end operating in the 2.4-GHz industrial-scientific-medical band. The proposed ESD protection structure is composed of a pair of ESD devices located near the RF pad, another pair close to the core circuit, and a high-quality integrated inductor connecting these two pairs. This structure can sustain a human body-model ESD level higher than 16 kV and a machine-model ESD level higher than 1 kV without degrading the RF performance of the front-end. A combined on-wafer transmission line pulse and RF test methodology for RF circuits is also presented confirming previous results. The front-end implements a zero-IF receiver. It has been implemented in a standard 2P6M 0.18-mu m CMOS process. It exhibits a voltage gain of 24 dB and a single-sideband noise figure of 8.4 dB, which make it suitable for most of the 2.4-GHz wireless short-range communication transceivers. The power consumption is only 1.06 mW from a 1.2-V voltage supply.