A single-chip PHS (Personal Handyphone System) transceiver IC (μPC8139GR) has been successfully developed by using microwave Si bipolar process technology (fT = 20 GHz). A transmitter block was composed of a quadrature modulator, up-converter, AGC (Automatic Gain Control) function for adjusting output level. A receiver block was composed of an IF down-converter, IF limiting amplifier, RSSI (Received Signal Strength Indicator) function and the second VCO (Voltage Controlled Oscillator) block. The transmitter and receiver function block could show the expected characteristics with low current consumption of 40.8 mA under 3 V supply conditions. This paper gives an outline of the design and the performances of this new PHS single-chip Si-MMIC.