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This paper describes a single-chip RF transceiver LSI for 2.4-GHz-band Gaussian frequency shift-keying applications, such as Bluetooth. This chip uses a 0.18-μm bulk CMOS process for lower current consumption. The LSI consists of almost all the required RF and IF building blocks: a transmit/receive antenna switch, a power amplifier, a low noise amplifier, an image rejection mixer, channel-selection filters, a limiter, a received signal strength indicator, a frequency discriminator, a voltage controlled oscillator, and a phase-locked loop synthesizer. The bandpass filter for channel selection was difficult to achieve since it operates at a low supply voltage. However, because large interference is roughly rejected at the output of the image rejection mixer and a wide-input-range bandpass filter with an optimized input bias is realized, the transceiver can operate at a supply voltage of 1.8 V. In the IF section, we adopted a circuit design using the minimum number of passive elements, resistors and capacitors, for a lower chip area of 10.2 mm2.