| High-efficiency radio frequency (RF) power amplifiers (PAs) are critical in portable battery-operated wireless communication systems, because they can dominate the DC power consumption in the transmit mode. To maximize the efficiency of the PA, a constant envelope modulation scheme is often employed, since the PA can operate in the high-efficiency or switched mode of operation (such as class D, E, F). However, with modern wireless communication systems evolving to a higher date rate, non-constant-envelope modulation schemes are preferred. This nonconstant envelope modulation requires highly linear PAs to avoid distortion of the signal.For the purpose of high efficiency and linearity of the PA, an envelope-elimination-and-restoration PA based on 0.18 μm SiGe BiCMOS process was designed. The main circuit is composed of four modules and they are envelope detector, envelope modulator, limiter and a class-E power amplifier. The class-E power amplifier is the core part of the whole circuit, since it can guarantee the high efficiency. Meanwhile, the Wilkinson power-combining technology was adopted to achieve a larger output power. In order to stand the high voltage of class-E power amplifier and release the influence of the bond wire inductor of source stage, a differential cascode topology was used. In addition, a notch filter network was utilized to satisfy the requirement of harmonics suppression. The design of the whole circuit and the pre-simulation results and post-simulation results are presented in this paper. The post-simulation results show that the maximum output power is 33.9dBm with the PAE of 47.3%, and the power gain is 23.9dB. The input VSWR is 1.4 and the 2nd and 3rd harmonic suppression are -54dBc and -71dBc.This designed envelope-elimination-and-restoration PA has large output power, high efficiency and decent harmonics suppression with a nice linearity. It can be applied in the transceiver systems which require high efficiency and linearity by further optimization. |
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