Research of V-band Active Frequency Multipliers and Efficiency/Linearity Enhancement and Hysteresis Phenomena of Microwave Power Amplifiers
Date Issued
2011
Date
2011
Author(s)
Kuo, Nai-Chung
Abstract
This thesis consists of two main parts, the first part is the design of two V-band frequency multipliers, and the second part is the related topics of microwave power amplifiers, including two K-band adaptive-bias power amplifiers with enhancement in back-off efficiency, a novel method for power amplifier linearization, and the discovery
and analysis of hysteresis phenomena in PA operation.
In the first part, the author presents a 52-75 GHz frequency quadrupler in 0.25-μm SiGe HBT and a 60-GHz frequency tripler in 0.15-μm pHEMT. The quadrupler features
a wideband performance and introduces the corresponding changes in performance when the operated condition of the quadrupler changes. As for the tripler, the author revised the conventional structure of active frequency tripler by proposing two novel ideas. The first is to explore the harmonic load tuning with resistance load, and the second is to exploit the produced fundamental power at the drain of the FET in order to improve the performances of the tripler.
The second part starts by presenting two K-band PAs, both fabricated in TSMC 0.18-μm CMOS, with adaptive bias technique that saves dc power when the PAs are operated with lower power levels. Although both the circuits involve the implement of a detector, the adaptive bias mechanisms in the two designs are realized by different methods, and the topologies of the two PAs are also different: the first one is a two-stage common-source amplifier and the second one is a two-stage cascode amplifier. Besides the introduction of the two PAs with their individual design methods and measured data, a brief comparison between the two works is also provided.
Successively, the author proposes a novel method to generate an auxiliary third-order intermodulaion (IM3) signal, which can be used in power amplifier linearization by canceling the output IM3 power. This auxiliary signal is not obtained by conventional methods as driving a highly nonlinear device or subtracting the fundamental power
from the output signal, but is simply achieved by exploiting the input reflected power of the main device. It is demonstrated that substantial IM3 power can be reflected to the source with little reflected fundamental power under some matching conditions of the device, and this feature can be utilized in the design of MMICs targeting excellent
output IM3 cancellation with a simple structure. A 25-GHz PHEMT power amplifier is designed and fabricated to exemplify the proposed technique with outstanding linearity.
The OIP3 of the proposed PA increases 14 dB from 25 to 39 dBm, and the output power enhances significantly from 5 to 14 dBm with －40-dB IM3 distortion (IMD3).
The second part ends with the analysis of an X-band pHEMT PA with dc and RF hysteresis. The unusual phenomena can be attributed to the gate current resulted from the impact ionization coupling with the gate bias resistor, which is usually observed in the design of RF circuits to provide the gate bias. After the gate current is considered, two methods are proposed to analyze the hysteresis with the same conclusion. The cause of the encountered hysteresis is for the first time identified, and criteria for the selection of the gate bias resistor in order to avoid the hysteresis are proposed. Finally, a power amplifier complying with these criteria is presented with good performances and without hysteresis.
Subjects
Frequency multiplier
power amplifier
MOS
MMIC
linearization
intermodulation distortion (IMD)
hysteresis
gate current
impact ionization
Type
thesis
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