Prediction of the Optimal Phase Shift between Control Signals in Dual-Input Power Amplifiers

This paper evaluates the effect of the phase shift between the two control signals in a dual-input load modulated balanced amplifier (LMBA). While the drain efficiency of the LMBA is not significantly affected by the phase shift between the control signals, the LMBA linearity instead can be significantly degraded if the phase shift parameter is not properly chosen. Therefore, we can predict the optimal phase shift between both LMBA control signals to enhance linearity levels when considering a 20 MHz bandwidth LTE transmission over a center frequency of operation ranging from 1.8 GHZ to 2.5 GHz. Experimental results showing the LBMA linearity and power efficiency after digital predistortion (DPD) linearization are presented. Finally, additional key parameters contributing to improve the LBMA power efficiency are discussed.

I. Introduction

With the increasing demand of data traffic, spectrum efficient modulation and access techniques occupying every time wider bandwidths are being proposed. Since 4G and now in 5G new radio, the use of Orthogonal Frequency Division Multiplexing (OFDM) is used to satisfy the requirements for higher transmission rates, but at the price of significantly increasing the signal’s peak-to-average power ratio (PAPR).