An improved method of power control with CMOS class-E power amplifiers

In this paper, an improved method of power control is introduced to widen the range of output power with high efficiency. Two CMOS class-E power amplifiers (PA) with different output power are adopted in the design. In order to eliminate the phase mismatch of two paths, a continuously adjustable CMOS phase shifter with a predictable phase transfer function is added before each PA. Meanwhile, the drain modulation technique is presented to vary the voltage supply of the amplification unit. With the combination of drain modulation and parallel amplification, a wider range of output power is obtained than the previous one. The amplifiers work in 915 MHz with the supply voltage of 1.8 V and 2.5 V. Simulation results show that the amplification unit could reach a maximum output power of 26 dBm and maintain a power- added efficiency (PAE) higher than 40% over the 18 dBm- 26 dBm output power range.