CMOS Supply Modulator for Envelope Tracking Power Amplifier
Date Issued
2015
Date
2015
Author(s)
Syu, Jin-Yan
Abstract
Nowadays, handheld devices are very popular, such as smartphone and Tablet.Because the handset devices use battery as the power source, customers are concerned about the battery life. Power amplifiers consume a significant portion of the total power of the RF Transmitters of the handheld devices. If power amplifiers can’t use power efficiently, the overall efficiency of RF Transmitters will become very poor. Envelope tracking is one of the techniques to improve the efficiency of the power amplifiers. Unlike a fixed-supply-voltage power amplifier, envelope tracking is a technique which the supply voltage of the power amplifier is dynamically adjusted by the supply modulator to track the envelope of the RF signal. In this thesis, the supply modulator includes two parts. One is the switching DC-DC converter which provides low frequency content of the envelope waveform, and the other is the linear amplifier which provides high frequency content of the envelope waveform. The supply modulator applied to envelope tracking not only has high bandwidth, but also has high slew rate. If we request the linear amplifier has both high bandwidth and high slew rate, it will consume a lot of power. This thesis proposes the circuits which can improve the slew rate of the linear amplifier. When needing high slew rate, the circuits can provide another charging or discharging path. With the method, the linear amplifier can reduce the power consumption. The chip is fabricated in a 0.13 μm CMOS with LDMOS process, and its size is 1.72*1.28 mm^2. The tracking signals are 1/5/10/15/20 MHz sine wave and 20 MHz LTE envelope. The output voltage range and the efficiency are 0.5~3.6 V and 77.3 %, respectively.
Subjects
Envelope tracking
Supply modulator
Switching DC-DC converter
Linear amplifier
Slew rate
Type
thesis