Abstract
Bitstream modulated transmitters may offer improved power efficiency and linearity simultaneously in RF power amplifiers. Several modulation techniques including envelop delta-sigma modulation and envelope pulse width modulation have been applied. The out-of-band quantization noise associated with these modulations may be rejected by a high-quality factor output filter, yet the in-band quantization noise needs to be further suppressed to meet the requirement of the emission mask. The proposed channelized active noise elimination technique can offer additional quantization noise suppression through software control without involving a passive filter. The essential concept is based on combining the outputs of multiple channels of Pas that have digitally controlled delays to form a FIR filter in analogue domain. A two-channel and a four-channel GaN power amplifiers are built to demonstrate this noise suppression concept and power combiners based on T-junction with quarter wavelength transmission line are proposed to retain the high power efficiency of the transmitters.
Highlights
GENERATION wireless communication aims at achieving high speed data transmission with advanced signal modulation techniques such as QAM or OFDM for their high spectral efficiency
To fully explore the switched-mode efficiency performance, we biased both main and auxiliary power amplifier (PA) deeper close to Class B when operating in pulsed load modulation (PLM) mode
The technique is applied to a combination of multiple high efficiency GaN power amplifiers
Summary
GENERATION wireless communication aims at achieving high speed data transmission with advanced signal modulation techniques such as QAM or OFDM for their high spectral efficiency. The increased peak-to-average power ratio (PAPR) of such modulations often requires the power transistors to operate at a significant back-off from its maximum output which compromises the overall power efficiency. Solutions to this problem include Doherty power amplifiers or envelop tracking (ET) techniques that can recover the power efficiency through either load modulations or supply modulations, while digital pre-distortion (DPD) is often leveraged to compensate for the nonlinearity. The first step is to re-modulate the original RF signal and
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