5 research outputs found
Development of an RF IV waveform based stress test procedure for use on GaN HFETs
This paper reports on the development of an RF IV waveform based stress test procedure. DC and low-voltage RF characterisation was carried out before and after high power RF stress. RF waveform measurements showed that the exact change in the RF load line induced during RF degradation cannot be directly inferred from the DC or low power RF measurement. The RF degradation takes the form of a knee-walkout, a small pinch-off shift consistent with charge trapping and defect generation, and in addition gate leakage occurs once the RF voltage exceeds a critical voltage
Low-frequency time-domain characterization for fast and reliable evaluation of microwave transistor performance
In this paper, we introduce the use of the low-frequency characterization of electron devices as an accurate and economical way to fast gather consistent data about the electron device performance at microwaves in the evaluation phase of new components, technologies and processes. © 2016 European Microwave Association
Analysis of the gate current as a suitable indicator for FET degradation under nonlinear dynamic regime
Electron device degradation, although not directly accounted for, represents a key issue in microwave circuit design. This is especially true when the particular applications involved (e.g., satellite, military, consumer) do not allow or strongly discourage any kind of maintenance. As a matter of fact, in order to account for device degradation in circuit design, a suitable electron device model is needed which is able to predict the performance degradation as a function of the actual electrical regime involved in the device operation. Such a kind of model is not available in literature. In this paper, quantitative results are provided for device degradation indicators which correlate DC and RF stress experiments. These results can be considered an important step toward the definition of a nonlinear model accounting for device
degradation
RF IV waveform engineering applied to VSWR sweeps and RF stress testing
This thesis looks at how the Radio Frequency (RF) waveform
measurement and engineering techniques developed for Power Amplifier
(PA) design can be used to investigate RF reliability. Within this area two
major themes are concentrated on – firstly the effect of a load impedance
mismatch and secondly an investigation into using the RF IV waveform
measurement system for RF stress testing.
The initial aim for this work was to investigate the potential for removing
the output protection isolator from a PA. It was seen that in doing so there is
the potential to cause an impedance mismatch, which results in a portion of
the power produced being reflected back. It was shown that the conditions
that could be presented to a device as a result of an impedance mismatch
can be found by performing a Voltage Standing Wave Ratio (VSWR) sweep.
The results of the worst possible case scenario VSWR sweep, when all of
the power is reflected back, can be split into three regions. One of high RF
drain voltage swings, one of high RF drain currents and a transition region of
simultaneously high RF drain currents and voltage swings. Each of these
regions presents different operating conditions to the device, and in turn
different stresses.
The second part of this thesis concentrates on an investigation into
Gallium Nitride (GaN) Heterostructure Field Effect Transistor (HFET)
reliability, specifically if the RF waveform measurement system can be used
to provide detailed information about the state of the device during RF stress
testing. A stress testing procedure was developed to allow this, which
featured both DC and RF characterisation measurements before and after
every stress period. It was shown that the measurements made during the
characterisation stages only gives a representation of the degradation seen
in the same measurements during the RF stress period
DESIGN TECHNIQUES FOR HIGH-EFFICIENCY MICROWAVE POWER AMPLIFIERS
The increasingly diffusion of wireless devices during the last years has established a sort of
“second youth” of analog electronics related to telecommunication systems. Nowadays, in fact,
electronic equipments for wireless communication are exploited not only for niche sectors as
strategic applications (e.g., military, satellite and so on): as a matter of fact, a large number of
commercial devices exploit wireless transmitting systems operating at RF and microwave
frequencies.
As a consequence, increasing interest has been focused by academic and industrial communities
on RF and microwave circuits and in particular on power amplifiers, that represent the core of a
wireless transmitting system. In this context, more and more challenging performance are
demanded to such a kind of circuit, especially in terms of output power, bandwidth and efficiency.
The present thesis work has been focused on RF and microwave power amplifier design that, as
said before, represents one of most actual and attractive research theme. Several aspects of such
topic have been covered, from the analysis of different design techniques available in literature to
the development of an innovative design approach, providing many experimental results related to
realized power amplifiers. Particular emphasis has been given to high-efficiency power amplifier
classes of operation, that represent an hot issue in a world more and more devoted to the energy
conservation. Moreover, electron device degradation phenomena were investigated, that although
not directly accounted for, represent a key issue in microwave power amplifier design.
In particular, the first chapter of this thesis provides an overview of commonly adopted design
methodologies for microwave power amplifier, analyzing the advantages and the critical aspects of
such approaches. Moreover, nonlinear device modeling issues oriented to microwave power
amplifier design have been dealt with.
In the second chapter, an innovative design technique is presented. It is based on experimental
electron device nonlinear characterization, carried out by means of a low-frequency large signal
measurement setup, in conjunction with the modeling of high-frequency nonlinear dynamic
phenomena. Several design examples have been carried out by exploiting the proposed approach
that confirm the effectiveness of the design technique.
In the third chapter, the proposed design methodology has been applied to high-efficiency power
amplifier classes of operations, that need to control the device terminations not only at the
fundamental frequency, but also at harmonics. Two high-efficiency power amplifiers have been realized by adopting such a technique, demonstrating performance in terms of output power and
efficiency comparable with the state of the art.
Finally, in chapter four an important power amplifier design aspect has been dealt with, related
to degradation and performance limitation of microwave electron devices. Several experimental
results have been carried out by exploiting a new measurement setup, oriented to the
characterization of degradation phenomena of microwave electron devices