43 research outputs found
Constraint-driven RF test stimulus generation and built-in test
With the explosive growth in wireless applications, the last decade witnessed an ever-increasing test challenge for radio frequency (RF) circuits. While the design community has pushed the envelope far into the future, by expanding CMOS process to be used with high-frequency wireless devices, test methodology has not advanced at the same pace. Consequently, testing such devices has become a major bottleneck in high-volume production, further driven by the growing need for tighter quality control.
RF devices undergo testing during the prototype phase and during high-volume manufacturing (HVM). The benchtop test equipment used throughout prototyping is very precise yet specialized for a subset of functionalities. HVM calls for a different kind of test paradigm that emphasizes throughput and sufficiency, during which the projected performance parameters are measured one by one for each device by automated test equipment (ATE) and compared against defined limits called specifications. The set of tests required for each product differs greatly in terms of the equipment required and the time taken to test individual devices. Together with signal integrity, precision, and repeatability concerns, the initial cost of RF ATE is prohibitively high. As more functionality and protocols are integrated into a single RF device, the required number of specifications to be tested also increases, adding to the overall cost of testing, both in terms of the initial and recurring operating costs.
In addition to the cost problem, RF testing proposes another challenge when these components are integrated into package-level system solutions. In systems-on-packages (SOP), the test problems resulting from signal integrity, input/output bandwidth (IO), and limited controllability and observability have initiated a paradigm shift in high-speed analog testing, favoring alternative approaches such as built-in tests (BIT) where the test functionality is brought into the package. This scheme can make use of a low-cost external tester connected through a low-bandwidth link in order to perform demanding response evaluations, as well as make use of the analog-to-digital converters and the digital signal processors available in the package to facilitate testing. Although research on analog built-in test has demonstrated hardware solutions for single specifications, the paradigm shift calls for a rather general approach in which a single methodology can be applied across different devices, and multiple specifications can be verified through a single test hardware unit, minimizing the area overhead.
Specification-based alternate test methodology provides a suitable and flexible platform for handling the challenges addressed above. In this thesis, a framework that integrates ATE and system constraints into test stimulus generation and test response extraction is presented for the efficient production testing of high-performance RF devices using specification-based alternate tests. The main components of the presented framework are as follows:
Constraint-driven RF alternate test stimulus generation: An automated test stimulus generation algorithm for RF devices that are evaluated by a specification-based alternate test solution is developed. The high-level models of the test signal path define constraints in the search space of the optimized test stimulus. These models are generated in enough detail such that they inherently define limitations of the low-cost ATE and the I/O restrictions of the device under test (DUT), yet they are simple enough that the non-linear optimization problem can be solved empirically in a reasonable amount of time.
Feature extractors for BIT: A methodology for the built-in testing of RF devices integrated into SOPs is developed using additional hardware components. These hardware components correlate the high-bandwidth test response to low bandwidth signatures while extracting the test-critical features of the DUT. Supervised learning is used to map these extracted features, which otherwise are too complicated to decipher by plain mathematical analysis, into the specifications under test.
Defect-based alternate testing of RF circuits: A methodology for the efficient testing of RF devices with low-cost defect-based alternate tests is developed. The signature of the DUT is probabilistically compared with a class of defect-free device signatures to explore possible corners under acceptable levels of process parameter variations. Such a defect filter applies discrimination rules generated by a supervised classifier and eliminates the need for a library of possible catastrophic defects.Ph.D.Committee Chair: Chatterjee, Abhijit; Committee Member: Durgin, Greg; Committee Member: Keezer, David; Committee Member: Milor, Linda; Committee Member: Sitaraman, Sures
Feature selection and feature design for machine learning indirect test: a tutorial review
International audienc
Publications of the Jet Propulsion Laboratory, 1984
The Jet Propulsion Laboratory (JPL) bibliography 39-26 describes and indexes by primary author the externally distributed technical reporting, released during calendar year 1984, that resulted from scientific and engineering work performed, or managed, by the Jet Propulsion Laboratory. Three classes of publications are included: (1) JPL Publications (82-, 83-, 84-series, etc.), in which the information is complete for a specific accomplishment; (2) articles from the quarterly Telecommunications and Data Acquisition (TDA) Program Report (42-series); and (3) articles published in the open literature
AFIT School of Engineering Contributions to Air Force Research and Technology Calendar Year 1973
This report contains abstracts of Master of Science Theses, Doctoral dissertations, and selected faculty publications completed during the 1973 calendar year at the School of Engineering, Air Force Institute of Technology, at Wright-Patterson Air Force Base, Ohio
Modeling and Linearization of MIMO RF Transmitters
Multiple-input multiple-output (MIMO) technology will continue to play a vital
role in next-generation wireless systems, e.g., the fifth-generation wireless networks
(5G). Large-scale antenna arrays (also called massive MIMO) seem to be the most
promising physical layer solution for meeting the ever-growing demand for high
spectral efficiency. Large-scale MIMO arrays are typically deployed with high
integration and using low-cost components. Hence, they are prone to different
hardware impairments such as crosstalk between the transmit antennas and power
amplifier (PA) nonlinearities, which distort the transmitted signal. To avert the
performance degradation due to these impairments, it is essential to have mechanisms
for predicting the output of the MIMO arrays. Such prediction mechanisms are
mandatory for performance evaluation and, more importantly, for the adoption of
proper compensation techniques such as digital predistortion (DPD) schemes. This
has stirred a considerable amount of interest among researchers to develop new
hardware and signal processing solutions to address the requirements of large-scale
MIMO systems.
In the context of MIMO systems, one particular problem is that the hardware
cost and complexity scale up with the increase of the size of the MIMO system.
As a result, the MIMO systems tend to be implemented on a chip and are very
compact. Reduction of the cost by reducing the bill of material is possible when
several components are eliminated. The reuse of already existing hardware is an
alternative solution. As a result, such systems are prone to excessive sources of
distortion, such as crosstalk. Accordingly, crosstalk in MIMO systems in its simplest
form can affect the DPD coefficient estimation scheme. In this thesis, the effect of
crosstalk on two main DPD estimation techniques, know as direct learning algorithm
(DLA) and indirect learning algorithm (ILA), is studied.
The PA behavioral modeling and DPD scheme face several challenges that seek
cost-efficient and flexible solutions too. These techniques require constant capture
of the PA output feedback signal, which ultimately requires the implementation
of a complete transmitter observation receiver (TOR) chain for the individual
transmit path. In this thesis, a technique to reuse the receiver path of the MIMO
TDD transceiver as a TOR is developed, which is based on over-the-air (OTA)
measurements. With these techniques, individual PA behavioral modeling and DPD
can be done by utilizing a few receivers of the MIMO TDD system. To use OTA
measurements, an on-site antenna calibration scheme is developed to individually
estimate the coupling between the transmitter and the receiver antennas.
Furthermore, a digital predistortion technique for compensating the nonlinearity
of several PAs in phased arrays is presented. The phased array can be a subset of
massive MIMO systems, and it uses several antennas to steer the transmitted signal
in a particular direction by appropriately assigning the magnitude and the phase
of the transmitted signal from each antenna. The particular structure of phased
arrays requires the linearization of several PAs with a single DPD. By increasing the
number of RF branches and consequently increasing the number of PAs in the phased
array, the linearization task becomes challenging. The DPD must be optimized to
results in the best overall linear performance of the phased array in the field. The
problem of optimized DPD for phased array has not been addressed appropriately in
the literature.
In this thesis, a DPD technique is developed based on an optimization problem
to address the linearization of PAs with high variations. The technique continuously
optimizes the DPD coefficients through several iterations considering the effect of
each PA simultaneously. Therefore, it results in the best optimized DPD performance
for several PAs.
Extensive analysis, simulations, and measurement evaluation is carried out as
a proof of concept. The different proposed techniques are compared with conventional approaches, and the results are presented. The techniques proposed in this
thesis enable cost-efficient and flexible signal processing approaches to facilitate the
development of future wireless communication systems
AFIT School of Engineering Contributions to Air Force Research and Technology Calendar Year 1973
This report contains abstracts of Master of Science Theses, Doctoral dissertations, and selected faculty publications completed during the 1973 calendar year at the School of Engineering, Air Force Institute of Technology, at Wright-Patterson Air Force Base, Ohio
Τεχνικές ελέγχου ορθής λειτουργίας και διόρθωσης επιδόσεων τηλεπικοινωνιακών ολοκληρωμένων κυκλωμάτων υψηλών συχνοτήτων
Στη διατριβή αυτή παρουσιάζονται τεχνικές ελέγχου ορθής λειτουργίας και
διόρθωσης επιδόσεων κατάλληλες για αναλογικά ολοκληρωμένα κυκλώματα RF.
Ειδικότερα, προτείνεται η ενοποίηση των διαδικασιών ελέγχου ορθής λειτουργίας
και διόρθωσης των επιδόσεων ενός κυκλώματος με την αξιοποίηση ενός συνόλου
βέλτιστα επιλεγμένων παρατηρήσιμων μεγεθών. Η επεξεργασία των μεγεθών αυτών
καθιστά δυνατή, αφενός, την ανίχνευση ελαττωμάτων και, αφετέρου, την πρόγνωση
των επιδόσεων του κυκλώματος η οποία επιτρέπει την εξέταση της συμμόρφωσής του
προς τις προδιαγραφές, καθώς και τη διόρθωση της συμπεριφοράς του. Προκειμένου
να αντιμετωπισθεί το πρόβλημα της προσβασιμότητας στα παρατηρήσιμα μεγέθη
προτείνεται ενσωματωμένη τεχνική μέτρησής τους, ενώ αναπτύσσεται μέθοδος για
την ελαχιστοποίηση της αβεβαιότητας που υπεισέρχεται στο ίδιο το σύστημα
μέτρησης. Εφαρμόζονται, επίσης, αλγόριθμοι επιλογής με σκοπό την μείωση του
αριθμού των παρατηρήσιμων μεγεθών, μέσω μιας διαδικασίας βελτιστοποίησης η
οποία οδηγεί στη μείωση του κόστους ελέγχου ορθής λειτουργίας με τον περιορισμό
της πολυπλοκότητας και της χρονικής διάρκειας διεξαγωγής του. Η αποδοτικότητα
των προτεινόμενων τεχνικών επιβεβαιώνεται με την εφαρμογή τους σε τυπικό μίκτη
RF τεχνολογίας 0.18μm CMOS, από τον οποίο λαμβάνονται αποτελέσματα
προσομοιώσεων που αξιολογούνται και συγκρίνονται με αντίστοιχες συμβατικές
τεχνικές.Testing and performance calibration techniques suitable for integrated RF
circuits are presented in this dissertation. Specifically, a common approach
is proposed for the testing and calibration procedures, that exploits a set of
optimally selected observables. The processing of these observables enables
defect detection, and also the prediction of the circuit’s performance which
allows the examination of compliance with the specifications and performance
calibration, as well. In order to address the problem of accessibility to test
observables, a built-in technique is proposed, while a method to minimize the
uncertainty introduced in the measurement system itself is also described. The
application of selection algorithms is explored, aiming to reduce the number of
test observables through an optimization procedure that leads to test cost
savings due to the reduction of the test conduction complexity and time. The
efficiency of the proposed techniques is validated by their application to a
typical RF mixer designed in a 0.18um CMOS technology. Simulation results are
obtained and assessed, while comparison with similar conventional techniques is
also provided
Novel power amplifier design using non-linear microwave characterisation and measurement techniques
This thesis, addresses some aspects of the well-known, problem, experienced by designer of
radio frequency power amplifiers (RFPA): the efficiency/linearity trade-off. The thesis is
focused on finding and documenting solution to linearity problem than can be used to
advance the performance of radio frequency (RF) and microwave systems used by the
wireless communication industry. The research work, this was undertaken by performing a
detailed investigation of the behaviour of transistors, under complex modulation, when
subjected to time varying baseband signals at their output terminal: This is what in this thesis
will be referred to as “baseband injection”. To undertake this study a new approach to the
characterisation of non-linear devices (NLD) in the radio frequency (RF) region, such as
transistors, designated as device-under-test (DUT), subjected to time varying baseband
signals at its output terminal, was implemented. The study was focused on transistors that are
used in implementing RF power amplifiers (RFPA) for base station applications. The nonlinear
device under test (NL-DUT) is a generalisation to include transistors and other nonlinear
devices under test. Throughout this thesis, transistors will be referred to as ‘device’ or
‘radio frequency power amplifier (RFPA) device’. During baseband injection investigations
the device is perturbed by multi-tone modulated RF signals of different complexities. The
wireless communication industry is very familiar with these kinds of devices and signals.
Also familiar to the industry are the effects that arise when these kind of signal perturb these
devices, such as inter-modulation distortion and linearity, power consumption/dissipation and
efficiency, spectral re-growth and spectral efficiency, memory effects and trapping effects.
While the concept of using baseband injection to linearize RFPAs is not new the
mathematical framework introduced and applied in this work is novel. This novel approach
NOVEL POWER AMPLIFIER DESIGN USING NON-LINEAR MICROWAVE CHARACTERISATION AND MEASUREMENT TECHNIQUES CARDIFF UNIVERISTY - UK
ABSTRACT vi
has provided new insight to this very complex problem and highlighted solutions to how it
could be a usable technique in practical amplifiers.
In this thesis a very rigorous and complex investigative mathematical and measurement
analysis on RFPA response to applied complex stimulus in a special domain called the
envelope domain was conducted. A novel generic formulation that can ‘engineer’ signal
waveforms by using special control keys with which to provide solution to some of the
problems highlighted above is presented.
The formulation is based on specific background principles, identified from the result of both
mathematical theoretical analysis and detailed experimental device characterisation
Advanced digital predistortion of power amplifiers for mobile and wireless communications
This research work focuses on improving the performances of digital predistorters while maintaining low computational complexity for mobile and wireless communication systems. Initially, the thesis presents the fundamental theory of power amplifiers, overview of existing linearisation and memory-effects compensation techniques and reveals the current issues in the field. Further, the thesis depicts the proposed solutions to the problems, including the developed in-band distortion modelling technique, model extraction methods, memoryless digital predistortion technique based on distortion components iterative injection, baseband equalisation technique for minimising memory effects, Matlab-ADS co-simulation system and adaptation circuit with an offline training scheme. The thesis presents the following contributions of the research work.
A generalized in-band distortion modelling technique for predicting the nonlinear behaviour of power amplifiers is developed and verified experimentally. Analytical formulae are derived for calculating predistorter parameters.
Two model extraction techniques based on the least-squares regression method and frequency-response analysis are developed and verified experimentally. The area of implementation and the trade-off between the methods are discussed.
Adjustable memoryless digital predistortion technique based on the distortion
components iterative injection method is proposed in order to overcome the distortion compensation limit peculiar to the conventional injection techniques.
A baseband equalisation method is developed in order to provide compensation of
memory effects for increasing the linearising performance of the proposed predistorter. A combined Matlab-ADS co-simulation system is designed for providing powerful
simulation tools.
An adaptation circuit is developed for the proposed predistorter for enabling its adaptation to environmental conditions.
The feasibility, performances and computational complexity of the proposed digital predistortion are examined by simulations and experimentally. The proposed method is tuneable for achieving the best ratio of linearisation degree to computational complexity for any particular application