Newsroom
Headlines
Calendar
Seminar Series
Publications
Media Information
A Low Noise, High Efficiency Envelope Modulator Structure for EDGE Polar Modulation
Jifeng Qin
Date: 2008-03-24
Degree: MS - Electrical Engineering
Advisory Committee
Dr. Alex Q. Huang - Committee ChairDr. Kevin Gard - Committee Member
Dr. Subhashish Bhattacharya - Committee Member
Abstract
Dynamic supply of power amplifiers in wireless transmitters can overcome the linearity-efficiency tradeoff issue in power amplifiers design, and envelope modulator is the key block in the dynamic supply system, low noise and high efficiency implementations are of many people's interests. Power management issues in envelope modulators for polar modulation are becoming increasingly complex and challenging. Both voltage step up and step down functions are required based on the input and output voltage ranges, the envelope modulator should have enough bandwidth to pass the modulated fast changing signal without distortion, and the output spectrum of the envelope modulator should meet stringent wireless standard specifications. High efficiency, high bandwidth and low noise requirements make envelope modulator design very challenging, and traditional switch mode power supplies like buck-boost converters cannot provide good spectrum results because of their high noise boost region. Comparing with switching mode power supplies, charge pumps have several advantages in terms of low noise and high efficiency, in this thesis, a novel two stage envelope modulator structure is proposed by using a voltage doubler followed with a 10MHz buck converter, this modulator achieves high efficiency, and the switching noise is reduced by 50dB compared to 4 switch buck boost converter (4SBBC) solution, the spectrum simulation results meet the EDGE wireless standard.
Download the complete document from the NCSU Libraries: 
