Design Of 2.45GHz Silicon Based Envelope Tracking Power Amplifier For LTE Applications

In order to deliver high data rates, the complex and spectral-efficient modulation schemes are adopted in modern wireless communication systems. These complex modulated signals are usually inherent non-constant envelope signals with high peak-to-average power ratio (PAPR), which brings low efficiency of the power amplifiers. To improve the efficiency, the envelope tracking power amplifier (ETPA) architecture has been proposed. Due to its feature of high efficiency over a wide power range, the ETPA is especially suitable in the applications of 4G LTE mobile communication which have a great development in the recent years.This paper presents the design and implementation of envelope tracking power amplifier for long-term evolution (LTE) applications, The ETPA is based on 0.18μm SiGe BiCMOS process and its operating band is from 2.4GHz to 2.5GHz. The entire envelope tracking power amplifier system has a combined structure with a linear class-AB power amplifier and a wideband high efficiency envelope modulator (EM). The EM tracks the amplitude of the input signal dynamically and then supplies the voltage of PA to improve efficiency. The pseudo-differential structure was adopted in the power amplifier to reduce the influence of parasitic inductance on the ground bondwires. What’s more, the cascade topology was adopted in the PA to stand the high voltage. The input matching and output matching were implemented by off-chip components to reduce losses. In the post simulation with sinusoidal signal, the class-AB PA achieves a saturated power of 31.06 dBm under the 5.0 V supply with a power added efficiency (PAE) of 42.64%. And the output 1dB compression point of the class-AB PA reaches 28.04 dBm. The ET-PA achieves an average output power of 24.67 dBm with 24.22% average PAE using an LTE 16QAM 5MHz signal for post simulation.The envelope tracking power amplifier designed in this paper has correct functions with high efficiency. It can be applied to LTE mobile communication handsets after further optimization.