Efficient radio frequency power amplifiers for wireless communications
Nowadays there has been increasing demand for radio frequency (RF) power amplifiers (PAs) to have high efficiency so as to extend wireless terminal’s battery/talk time and achieve low form-factor in mobile, as well as reduce the cooling and electrical power cost in base stations. The classical design equations of efficient switching-mode class E PAs have been challenged by non-ideal issues which can lead the analysis of class E PAs to be enormously complex and intractable. In this work, the design of class E pHEMT PA has been improved based on the ADS load-pull simulation, which permits an iterative search for the nominal impedance values that maximize efficiency and output power under various bias/load conditions of the active transistor. An important contribution of this dissertation is the proposed multi-harmonic real-time active load-pull (RT-ALP) based on the large signal network analyzer (LSNA), for designing high efficiency non-linear PAs. It applies real-time tunings at the second and third harmonic frequencies, which enable to quickly synthesize a wide range of harmonic load reflection coefficients without stability issue due to open-loop structure. Fast acquisition of reliable large-signal data generates the RF dynamic loadlines, PAE and power contour plots for guiding the design of non-linear PAs. A GaN HEMT demonstrats a PAE of 81% (class F) at 2 GHz by tuning up to the third harmonic. Based on the predicted optimal impedances, a pHEMT PA is designed and constructed with matching networks achieving 68.5% PAE at 2 GHz, further demonstrating the efficacy and reliability of the proposed multi-harmonic RT-ALP for the interactive design of power efficient PAs. An integrated CMOS Doherty PA for 3.5 GHz WiMAX is designed using the 0.18µm TSMC CMOS. Cascode transistors are chosen to achieve high efficiency and address the low breakdown voltage issue. Lumped components replace the ?/4 transmission line for circuitry miniature. The layout passes all the DRC/LVS checks and is implemented with the novel GSML methodology for parasitics control. Compact integrated diode linearizers are utilized to improve IMD3 up to 5.75 dBc. The Doherty PA achieves a 24.5 dBm output power of and 43% PAE at 3.5 GHz.
School:The Ohio State University
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:radio frequency rf power amplifier pa non linear class e f doherty load pull large signal network analyzer lsna fundamental harmonic high efficiency pae phemt gan cmos ground shielded microstrip line gsml layout
Date of Publication:01/01/2007