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1.	Rantakokko, Jouni, et al. (författare) Accurate and Reliable Soldier and First Responder Indoor Positioning : Multi-Sensor Systems and Cooperative Localization 2011 Ingår i: IEEE wireless communications. - : IEEE Communications Society. - 1536-1284 .- 1558-0687. ; 18:2, s. 10-18 Tidskriftsartikel (refereegranskat)abstract A robust, accurate positioning system with seamless outdoor and indoor coverage is a highly needed tool for increasing safety in emergency response and military urban operations. It must be lightweight, small, inexpensive, and power efficient, and still provide meter-level accuracy during extended operations. GPS receivers, inertial sensors, and local radio-based ranging are natural choices for a multisensor positioning system. Inertial navigation with foot-mounted sensors is suitable as the core system in GPS denied environments, since it can yield meter-level accuracies for a few minutes. However, there is still a need for additional supporting sensors to keep the accuracy at acceptable levels during the duration of typical soldier and first responder operations. Suitable aiding sensors are three-axis magnetometers, barometers, imaging sensors, Doppler radars, and ultrasonic sensors. Furthermore, cooperative positioning, where first responders exchange position and error estimates in conjunction with performing radio-based ranging, is deemed a key technology. This article provides a survey on technologies and concepts for high accuracy soldier and first responder positioning systems, with an emphasis on indoor positioning.
2.	Rantakokko, Jouni, et al. (författare) Positioning of emergency personnel in rescue operations : 2007 Rapport (övrigt vetenskapligt/konstnärligt)abstract Summary and recommendations Presently, GPS-equipped mobile phones are launched at a large scale, enabling a variety of positioning based services. Indeed, GPS is expected to be the future killer application for mobile phones and services. The concept of accurate positioning by technical means implies a large number of applications not only for the mass market, but also for rescue services, fire brigades, police forces, and military and so on. For professional and governmental safety-of-life services the current systems are far from usable and large efforts have to be concentrated on research and development. Technologies based on GPS and other satellite-based positioning systems alone are vulnerable and are expected to malfunction in indoor or challenging electromagnetic environments, or due to antagonistic measures. Satellite-based positioning is a key component in a robust communication and positioning system aimed for first responders. Satellite based positioning in combination with local radio-based positioning systems and dead-reckoning or inertial navigation systems are enablers to fulfill the users? requirements on accuracy and availability of the positioning service. Sweden is a competent player within security. Around 300 companies with some 22.000 employees have been identified within the area. Swedish industry, research institutes and universities are expected to take part in international consortiums within EU FP7, as well as being a player within DHS funded research and development within the personal positioning and navigation area. The market potential for professional and safety-of-life personal equipment for robust positioning and communication with suitable means for information presentation is significant. In the US and the EU there are some 2 million incident responders each. On a national level we count some 35.000 fire fighters, police, and military personnel in international operations. A migration of the technology to private end-consumers as implemented in consumer electronics opens up a gigantic market for wireless services within navigation, gaming, and position-awareness services. Within the project positioning of first responders in rescue operations, robust positioning has been studied. From a system perspective, technologies for positioning of personnel are key system components within a platform for positioning, information transfer for command and control, and information processing and presentation for the personnel at all levels. \? Systems for training are needed to introduce the end-user to the technology, and for training and simulation of novel strategies enabled by the technology. Stationary training systems can be implemented with state-of-the art positioning methods. Feedback from the end-user to the R&D community is instrumental in the specification and development of future means for positioning of first responders. A research infrastructure, or test-bed, for implementation and evaluation of robust positioning is an essential tool. \? The functionality of the equipment has to be robust against hostile electromagnetic environments, either due to the actual physical environment (indoor scenario, intersystem interference from nearby electronic equipment, scenario within a large steel constructions, or power plant, etc), or due to electronic warfare antagonistic actions. Research has to be performed in several areas such as channel characterization for radio positioning, quality of satellite signals subjected to interference, and integrity of sensor information due to external influences. \? Contemporary MEMS-technology provides small-size sensors with low energy consumption. The rapid development within sensor technologies enables data fusion from a plurality of sensors by digital signal processing. Fundamental issues within digital signal processing have to be studied in several fields, including methods to enhance sensor performance by incorporating behavioral modeling; fusion of digital information from a plurality of sensors; aspects of hardware implementation to fulfill requirements on size, weight and uptime, and software defined receivers for radio-based positioning, communication and mapping. In summary, future systems for positioning of first responders in rescue operations rely on the development of infra-structure aimed for end-users in a training scenario; and a platform for R&D-purposes. In parallel, fundamental issues have to be studied regarding the electromagnetic environment, as well as methodologies in digital signal processing.
3.	Strömback, Peter, et al. (författare) Foot-Mounted Inertial Navigation and Cooperative Sensor Fusion for Indoor Positioning 2010 Ingår i: Proceedings of the 2010 International Technical Meeting of The Institute of Navigation. - 9781617381157 ; , s. 89-98 Konferensbidrag (refereegranskat)abstract In this paper we examine the effect of introducing an opportunistic cooperative navigation approach between soldiers, or first responders, equipped with foot-mounted IMUs and UWB-ranging equipment. The foot-mounted navigation system is based on a 15-state Extended Kalman filter, utilizing zero-velocity updates. The addition of range measurements between cooperative units displayed a significant improvement of the navigation accuracy in the studied scenarios. This approach has the potential to enable accurate positioning for several minutes in GPS-denied environments. Furthermore, the performance of the UWB-ranging sensor is examined and the resulting error statistics and typical ranging distances are characterized in indoor environments.
4.	Ahnström, Ulrika, et al. (författare) Detection and direction-finding of spread spectrum signals using correlation and narrowband interference rejection 2003 Ingår i: Nordic Matlab Conference 2003. Konferensbidrag (refereegranskat)abstract An algorithm for correlation-based detection of direct sequence spread spectrum signals with direction finding, including direction-filtering and narrow-band interference rejection, is implemented and evaluated in MATLAB. An analog noise-free signal is generated and sampled by a test-bed system. Numerical simulations are run based on data corrupted by mutually uncorrelated white Gaussian noise sequences, and also with recorded noise from two spatially separated HF radio receivers. The simulations and measurements show promising results for detection and direction-finding of covert wideband signals in low SNR and in presence of narrowband interferers. Direction filtering is shown to improve the results.
5.	Amin, Shoaib, et al. (författare) 2D Extended envelope memory polynomial model for concurrent dual-band RF transmitters 2017 Ingår i: International journal of microwave and wireless technologies. - : Cambridge University Press. - 1759-0795 .- 1759-0787. ; 9:8, s. 1619-1627 Tidskriftsartikel (refereegranskat)abstract The paper presents a 2D extended envelope memory polynomial (2D-EEMP) model for concurrent dual-band radio frequency (RF) power amplifiers (PAs). The model is derived based on the physical knowledge of a dual-band RF PA. The derived model contains cross-modulation terms not included in previously published models; these terms are found to be of importance for both behavioral modeling and digital pre-distortion (DPD). The performance of the derived model is evaluated both as the behavioral model and DPD, and the performance is compared with state-of-the-art2D-DPD and dual-band generalized memory polynomial (DB-GMP) models. Experimental result shows that the proposed model resulted in normalized mean square error (NMSE) of -51.7/-51.6dB and adjacent channel error power ratio (ACEPR) of -63.1/-63.4 dB, for channel 1/2, whereas the 2D-DPD resulted in the largest model error and DB-GMP resulted in model parameters that are 3 times more than those resulted with the proposed model with the same performance. As pre-distorter, the proposed model resulted in adjacent channel power ratio (ACPR) of -55.8/ -54.6 dB for channel 1/2 and is 7-10 dB lower than those resulted with the 2D-DPD model and2-4 dB lower compared to the DB-GMP model.
6.	Amin, Shoaib, 1985-, et al. (författare) Rebuttal to "On Dual-Band Amplifications Using Dual Two-Tones Clarifications and Discussions" 2017 Ingår i: IEEE Transactions on Instrumentation and Measurement. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0018-9456 .- 1557-9662. ; 66:10, s. 2795-2797 Tidskriftsartikel (refereegranskat)abstract This rebuttal is to "On dual-band amplifications using dual two-tone: Clarifications and discussion." In the following, we provide our reply.
7.	Andersson, Tomas, et al. (författare) Frequency estimation by 1-bit quantization and table look-up processing 2000 Ingår i: Proceedings European Signal Processing Conference. ; , s. 1807-1810 Konferensbidrag (refereegranskat)
8.	Andersson, Tomas, et al. (författare) Frequency estimation utilizing the Hadamard transform 2001 Ingår i: 2001 IEEE WORKSHOP ON STATISTICAL SIGNAL PROCESSING PROCEEDINGS. - NEW YORK : IEEE. - 0780370112 ; , s. 409-412 Konferensbidrag (refereegranskat)abstract Fast analog to digital conversion with only one bit per sample does not only make high sampling rates possible but also reduces the required hardware complexity. For short data buffers or block lengths, it has been shown that tone frequency estimators can be implemented by a simple table look-up. In this paper we present an analysis of such tables using the Hadamard transform. As an outcome of the analysis, we propose a class of nonlinear estimators of low complexity. Their performance is evaluated using numerical simulations. Comparisons are made with the proper Cramer-Rao bound and with the table look-up approach.
9.	Andersson, Tomas, et al. (författare) IEEE Standard 1057, Cramér-Rao Bound and the Parsimony Principle 2003 Ingår i: International Workshop on ADC Modelling and Testing. ; , s. 231-234 Konferensbidrag (refereegranskat)
10.	Andersson, Tomas, et al. (författare) IEEE standard 1057, Cramer-Rao bound and the parsimony principle 2006 Ingår i: IEEE Transactions on Instrumentation and Measurement. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9456 .- 1557-9662. ; 55:1, s. 44-53 Tidskriftsartikel (refereegranskat)abstract This paper deals with some fundamental properties of the sine-wave-fit algorithm included in IEEE Standards 1057 and 1241. Asymptotic Cramer-Rao bounds (CRBs) for three and four model parameters are derived under the Gaussian assumption. Further, the sine-wave-fitting properties of the algorithm are analyzed by the parsimony principle. A decision criterion whether to use the three- or four-parameter model is derived. It is shown that a three-parameter sine-wave fit produces a better fit than the four-parameter fit if the frequency is known to be within an interval related to the number of samples and the signal-to-noise ratio. By a numerical analysis, the theoretical results are shown to be also valid for the uniform noise model of quantization.
11.	Andersson, Tomas, et al. (författare) Multiple-tone estimation by IEEE standard 1057 and the expectation-maximization algorithm 2003 Ingår i: IMTC/O3: PROCEEDINGS OF THE 20TH IEEE INSTRUMENTATION AND MEASUREMENT TECHNOLOGY CONFERENCE. ; , s. 739-742 Konferensbidrag (refereegranskat)abstract The aim of this work is to present an efficient algorithm for multiple-tone parameter estimation. The algorithm is inspired by the expectation-maximization algorithm, and it utilizes the IEEE standard 1057 for single tone parameter estimation. In the derivation of the algorithm it is assumed that the number of tones are known and that the frequencies are well separated The algorithm is evaluated using data consisting of multiple real-valued tones. The performance of the frequency estimator is studied and compared with the asymptotic Cramer-Rao bound (CRB). It is shown that the algorithm produces statistically efficient frequency estimates at high signal to noise ratios, that is the variance of the estimates reaches the CRB. Finally, it is shown that the algorithm can produce efficient estimates independent of the number of tones in the input signal.
12.	Andersson, Tomas, et al. (författare) Multiple-tone estimation by IEEE standard 1057 and the expectation-maximization algorithm 2005 Ingår i: IEEE Transactions on Instrumentation and Measurement. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9456 .- 1557-9662. ; 54:5, s. 1833-1839 Tidskriftsartikel (refereegranskat)
13.	Andersson, Tomas, et al. (författare) Robustness of wave-fitting with respect to uncertain parameter values 2005 Ingår i: Instrumentation and Measurement Technology Conference, 2005. IMTC 2005. Proceedings of the IEEE. ; , s. 662-665 Konferensbidrag (refereegranskat)abstract This paper presents a criterion for model order selection. By usage of the parsimony principle the mean sum-squareerror is evaluated for models subject to imperfections inparameter values. In particular, model imperfections in different sinewavefitting scenarios have been analyzed. The analysis is carried out considering linear models. The obtained result is generalized to models incorporating non-linear parameters. Numerical illustrations are provided in order to gain insight of the behavior of model imperfections, as well as to numerically verify the theoretical results. The main contributions include a general result for linear signal models, as well as some novel results on sinewave-fitting.
14.	Andersson, Tomas, et al. (författare) Standardized sine-wave fitting algorithms, extensions and applications 2003 Ingår i: Northern Light Workshop on Sensors, Signals and Systems, Björkliden, Sverige, April 7-9, 2003. Konferensbidrag (refereegranskat)abstract The objective of this paper is to present the statistical properties of the IEEE-STD-1057/IEEE-STD-1241 sine-wave fitting algorithms. The proper Cramér-Rao bound is derived for both the three-parameter and four-parameter algorithms. Further, we investigate the residual, and derive its statistical properties, in both the three- and four-parameter fitting case. In a practical setup were the frequency is almost known, we derive an analytical expression for the mean of the residual. By analysis we compare the two methods and state in which case one should use one over the other. Finally, we present some numerical evaluations confirming our analytical findings.
15.	Andersson, Tomas, et al. (författare) Toward a Standardized Multi-Sinewave Fit Algorithm 2004 Ingår i: 9th European Workshop on ADC Modelling and Testing. - 9781634391849 ; , s. 337-342 Konferensbidrag (refereegranskat)abstract Multi-sinewave test methods require algorithms for multiple-tone parameter estimation.There exist a vast amount of publications on the topic [1]. This paper presents a generalization ofthe IEEE four-parameter sinewave ﬁt algorithm suitable to handle data comprising multiple sinewaves.The proposed method directly estimates the 3p + 1 parameters of a p-tone model. The algorithmis analyzed numerically with emphasize on its convergence properties and statistical efﬁciency. Theinitialization of the algorithm is of major importance and an attempt to formulate a proper initializationprocedure is presented.
16.	Anttila, Lauri, et al. (författare) Joint Mitigation of Power Amplifier and I/Q Modulator Impairments in Broadband Direct-Conversion Transmitters 2010 Ingår i: IEEE transactions on microwave theory and techniques. - 0018-9480 .- 1557-9670. ; 58:4, s. 730-739 Tidskriftsartikel (refereegranskat)abstract In this paper, we present a novel digital predistorter structure for joint mitigation of frequency-dependent power amplifier (PA) and in-phase and quadrature (I/Q) modulator impairments in direct-conversion radio transmitters. The predistorter is based on an extended parallel Hammerstein structure, yielding a predistorter that is fully linear in the parameters. In the parameter estimation stage, the indirect learning architecture is utilized. The proposed technique is the first technique in the literature to consider the joint estimation and mitigation of frequency-dependent PAand I/Q modulator impairments. Extensive simulation and measurement analysis is carried out to verify the operation and efficacy of the proposed predistortion structure. It is shown that the adjacent channel power ratio is increased by more than 20 dB in all experiments when using the proposed method, and that the performance of the reference techniques is clearly exceeded.
17.	Anttila, L, et al. (författare) Recursive learning-based joint digital predistorter for power amplifier and I/Q modulator impairments 2010 Ingår i: International Journal of Microwave and Wireless Technologies. - : Cambridge University Press and the European Microwave Association. - 1759-0787. ; 2:2, s. 173-182 Tidskriftsartikel (refereegranskat)abstract The main implementation impairments degrading the performance of direct-conversion radio transmitters are in-phase/quadrature (I/Q) mismatch, local oscillator (LO) leakage, and power amplifier (PA) nonlinear distortion. In this article, we propose a recursive least-squares-based learning algorithm for joint digital predistortion (PD) of frequency-dependent PA and I/Q modulator impairments. The predistorter is composed of a parallel connection of two parallel Hammerstein (PH) predistorters and an LO leakage compensator, yielding a predistorter which as a whole is fully linear in the parameters. In the parameter estimation stage, proper feedback signal from the transmitter radio frequency (RF) stage back to the digital parts is deployed, combined with the indirect learning architecture and recursive least-squares training. The proposed structure is one of the first techniques to explicitly consider the joint estimation and mitigation of frequency-dependent PA and I/Q modulator impairments. Extensive simulation and measurement analysis is carried out to verify the operation and efficiency of the proposed PD technique. In general, the obtained results demonstrate linearization and I/Q modulator calibration performance clearly exceeding the performance of current state-of-the-art reference techniques.
18.	Bergenheim, Jon, et al. (författare) Ekosläckning 2002 Patent (populärvet., debatt m.m.)abstract The present invention relates to a cancellation of echoes in telecommunications systems, more specifically it relates to adaptive alignment of a linear filter (500) used for echo cancellation. According to the invention, it is continuously determined, by means of control logic (520), if a reflection replica delay included in an echo replica signal (110), which delay is provided by a signal buffer (510), should be attempted to be increased or not. Similarly, it is continuously determined if the reflection replica delay should be attempted to be decreased or not. In this way it is possible to provide a delay of the reflection replica which corresponds to the pure delay of a corresponding reflection included in an echo signal (120) received over an echo path. The invention is advantageous since the filter (500) will continuously and quickly adapt to changes in the echo path delay by continuously increasing or decreasing, in an incremental and smooth manner, a present replica delay.
19.	Bjorsell, Niclas, et al. (författare) Measuring Volterra kernels of analog to digital converters using a stepped three-tone scan 2006 Ingår i: 2006 IEEE INSTRUMENTATION AND MEASUREMENT TECHNOLOGY CONFERENCE PROCEEDINGS. - 9780780393592 ; , s. 1047-1050 Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract Volterra theory can be used to mathematically model nonlinear dynamic components such as analog-to-digital converter (ADC). This paper describes how frequency domain Volterra kernels of an ADC are determined from measurements. The elements of Volterra theory are given and practical issues are considered, such as methods for signal conditioning, finding the appropriate test signals scenario and suitable sampling frequency. The results show that for the used pipeline ADC, the frequency dependence is significantly stronger for second order difference products than for sum products and the linear frequency dependence was not as pronounced as that of the second order Volterra kernel.
20.	Bjorsell, Niclas, et al. (författare) Post-correction of under-sampled analog to digital converters 2007 Ingår i: 2007 IEEE INSTRUMENTATION & MEASUREMENT TECHNOLOGY CONFERENCE. - : IEEE. - 9781424405886 ; , s. 58-62 Konferensbidrag (refereegranskat)abstract Applications with wide bandwidth and high center frequencies force the analog to digital converter (ADC) to be active in a working range with less dynamic performance in relation to lower frequency bands. However using under-sampling techniques in combination with post-correction methods enable a combination of high sampling rate, wide bandwidth and low distortion. In this paper the employed dynamic post-correction is a combination of look-up tables and model based correction. The results are mainly based on measurements on a 12-bit 210 MSPS ADC. The improvement in total harmonic distortion and spurious free dynamic range are acceptable over a wide frequency range and it is robust to variations in amplitude.
21.	Björsell, Niclas, et al. (författare) A Statistical Evaluation of ADC Histogram Tests with Arbitrary Stimuli Signal 2005 Ingår i: ADDA 2005. ; , s. 259-264 Konferensbidrag (refereegranskat)
22.	Björsell, Niclas, et al. (författare) Achievable ADC Performance by Post-Correction Utilizing Dynamic Modeling of the Integral Nonlinearity 2008 Ingår i: EURASIP Journal on Advances in Signal Processing. - : Springer Science and Business Media LLC. - 1110-8657 .- 1687-6180 .- 1687-6172. ; , s. 497187-1-497187-10 Tidskriftsartikel (refereegranskat)abstract There is a need for a universal dynamic model of analog-to-digital converters (ADC’s) aimed for postcorrection. However, it is complicated to fully describe the properties of an ADC by a single model. An alternative is to split up the ADC model in different components, where each component has unique properties. In this paper, a model based on three components is used, and a performance analysis for each component is presented. Each component can be postcorrected individually and by the method that best suits the application. The purpose of postcorrection of an ADC is to improve the performance. Hence, for each component, expressions for the potential improvement have been developed. The measures of performance are total harmonic distortion (THD) and signal to noise and distortion (SINAD), and to some extent spurious-free dynamic range (SFDR).
23.	Björsell, Niclas, et al. (författare) Analog-to-Digital Converters for High-Speed Applications 2005 Ingår i: GigaHz 2005. ; , s. 151-154 Konferensbidrag (refereegranskat)
24.	Björsell, Niclas, et al. (författare) Benefits with Truncated Gaussian Noise in ADC Histogram Tests 2004 Ingår i: 9th IMEKO Workshop on ADC Modeling and Testing, IWADC 2004, Held Together with the 13th IMEKO TC4 Symposium on Measurements for Research and Industrial Applications. - : IMEKO-International Measurement Federation Secretariat. - 9781634391856 ; , s. 787-792 Konferensbidrag (refereegranskat)abstract One method to characterize ADCs is to use a histogram, where Gaussian noise may be used as stimulus signal. However, a Gaussian noise signal that excites all transition levels also generates input values outside working range of the ADC. Modern signal generators can generate arbitrary signals. Hence, excluding undesired values outside the ADC full scale can minimize test sequences. Truncating the signal to the working range gives further advantages, which are explored in this paper. The statistical properties is theoretically evaluated and compared. It is shown that accuracy increases for a fixed sample length and that variation over transition levels decrease.
25.	Björsell, Niclas, et al. (författare) Dynamic behavior models of analog to digital converters aimed for post-correction in wideband applications 2006 Ingår i: 18th IMEKO World Congress 2006: Metrology for a Sustainable Development. - 9781622766468 ; , s. 1344-1348, s. 5- Konferensbidrag (refereegranskat)abstract In this paper a dynamic behavior model of analog to digital converters is proposed. The model is aimed for post correction in wideband applications. The suggested post correction method is a combination of look up tables and model based correction.The model consists of three components. The first is a component represented by a Hammerstein model; that is a static nonlinearity followed by a time invariant linear filter. The second component is a nonparametric model caused by significant deviation from the characterized integral nonlinearity and the output from the Hammerstein model. The third component contains of the remaining deviation and is considered as a random model error.Results from simulations verify that the examined ADC can be described by an ordinary Hammerstein model and a static look-up table.
26.	Björsell, Niclas, et al. (författare) Histogram Tests for Wideband Applications 2008 Ingår i: IEEE Transactions on Instrumentation and Measurement. - 0018-9456 .- 1557-9662. ; 57:1, s. 70-75 Tidskriftsartikel (refereegranskat)abstract Characterization and testing of analog-to-digital converters (ADCs) are important for many reasons. A histogram test is a common method to characterize the linearity features of an ADC. Two commonly used stimulus signals are sine waves and Gaussian noise. This paper presents a metrological comparison between Gaussian and sine-wave histogram tests for wide-band applications, that is, we evaluate the performance of the characterization of the ADC and the usability of postcorrection. A postcorrection procedure involves the characterization of the ADC nonlinearity and then the use of this information by processing the ADC output samples to remove the distortion. The results show that the Gaussian histogram test gives reasonable accuracy in measuring nonlinearities. However, it does not result in a suitable model for postcorrection in wideband applications. A single-tone sine-wave histogram will be a better basis for postcorrection. The best result can be obtained if the lookup table is trained with several single-tone sine waves in the frequency band.
27.	Björsell, Niclas, 1964-, et al. (författare) Improved estimate of parametric models for analogue to digital converters by using weighted integral nonlinearity data 2010 Ingår i: 17th Symposium IMEKO TC4 - Measurement of Electrical Quantities, 15th International Workshop on ADC Modelling and Testing, and 3rd Symposium IMEKO TC19 - Environmental Measurements. - 9781617823381 ; , s. 597-600, s. 597-600 Konferensbidrag (refereegranskat)abstract Error modelling has played a major role in generating post-corrections of analogue to digital converters (ADC). Benefits by using parametric models for post-correction are that they requires less memory and that they are easier to identify for arbitrary signals. However, the parameters are estimated in two steps; firstly, the integral nonlinearity (INL) is estimated and secondly, the model parameters. In this paper we propose a method to improve the performance in the second step, by utilizing information about the statistical properties of the first step.
28.	Björsell, Niclas, et al. (författare) Kautz-Volterra modelling of an analogue-to-digital converter using a stepped three-tone excitation 2007 Ingår i: 12th IMEKO TC-4 International Workshop on ADC MODELLING AND TESTING. ; , s. 107-112 Konferensbidrag (refereegranskat)abstract In many test and measurement applications, the analogue-to-digital converter (ADC) is the limiting component. Using post-correction methods can improve the performance of the component as well as the over all measurement system. In this paper an ADC is characterised by a Kautz-Volterra (KV) model, which utilises a model-based post-correction of the ADC with general properties and a reasonable number of parameters. Results that are based on measurements on a high-speed 12-bit ADC, shows good results for a third order model.
29.	Björsell, Niklas, et al. (författare) Measuring Volterra Kernels of Analog To Digital Converters Using a Stepped Three-Tone Scan 2008 Ingår i: IEEE Transactions on Instrumentation and Measurement. - 0018-9456 .- 1557-9662. ; 57:4, s. 666-671 Tidskriftsartikel (refereegranskat)abstract The Volterra theory can be used to mathematically model nonlinear dynamic components such as analog-to-digital converters (ADCs). This paper describes how frequency-domain Volterra kernels of an ADC are determined from measurements. The elements of the Volterra theory are given, and practical issues are considered, such as methods for signal conditioning and finding the appropriate test signals scenario and suitable sampling frequency. The results show that, for the used pipeline ADC, the frequency dependence is significantly stronger for second-order difference products than for sum products and the linear frequency dependence was not as pronounced as that of the second-order Volterra kernel. It is suggested that the Volterra kernels have the symmetry properties of a specific box model, namely, the parallel Hammerstein system.
30.	Björsell, Niclas, 1964-, et al. (författare) Multi-tone design for out-of-band characterization of nonlinear RF modules using harmonic sampling 2010 Ingår i: 2010 IEEE International Instrumentation and Measurement Technology Conference, I2MTC 2010. - Piscataway, NJ : IEEE Service Center. - 9781424428335 - 9781424428328 ; , s. 620-623 Konferensbidrag (refereegranskat)abstract In this paper we evaluate the generation of a multi-tone set for characterizing the behavior of nonlinear radio frequency (RF) modules in its out-of-band when harmonic sampling is used as digitizer. The purpose is to provide the reader with a tool to select proper frequencies and record length for a given application and test-bed. The method is based on simulations and the use of Sidon sequences. The proposed method is applicable to sparse discrete frequency multi-tones.
31.	Björsell, Niclas, et al. (författare) On Gaussian and Sine Wave Histogram Tests for Wideband Applications 2005 Ingår i: Proceedings of the IEEE Instrumentation and Measurement Technology Conference. - : IEEE. - 9780780388796 ; , s. 677-682 Konferensbidrag (refereegranskat)abstract Characterization and testing of analog-to-digital converters (ADCs) are interesting in many different aspects. Histogram test is a common method to characterize the linearity features of an ADC. Two commonly used stimuli signals are sine waves and Gaussian noise. This paper will present a metrological comparison between Gaussian and sine wave histogram tests for wideband applications; that is evaluate the performance in characterization of the ADC and the usability of post-correction. A post-correction procedure involves characterization of the ADC non-linearity and then utilization of this information by processing the ADC output samples to remove the distortion. The results indicates that even though the Gaussian histogram test seems to give reasonable accuracy to measure non-linearities it is not thereby a suitable model for post-correction. A single-tone sine wave histogram will most likely be a better solution. Best result is to train the look-up table with several single-tone sine waves in the frequency band.
32.	Björsell, Niclas, et al. (författare) Truncated Gaussian Noise in ADC Histogram Tests 2007 Ingår i: Measurement. - : Elsevier BV. - 0263-2241 .- 1873-412X. ; 40:1, s. 36-42 Tidskriftsartikel (refereegranskat)abstract One method to characterize analogue to digital converters (ADCs) is to use a histogram, where Gaussian noise may be used as stimulus signal. However, a Gaussian noise signal that excites all transition levels also generates input values outside working range of the ADC. Modern signal generators can generate arbitrary signals. Hence, excluding undesired values outside the ADC full scale can minimize test sequences. Truncating the signal to the working range gives further advantages, which are explored in this paper. The Cramer-Rao lower bound and a minimum variance estimator for histogram tests with an arbitrary stimulus are derived. These are applied for truncated Gaussian noise and the result is theoretically evaluated and compared to untruncated noise. It is shown that accuracy increases for a fixed sample length and that variation over transition levels decrease.
33.	Bose, Subhojyoti, et al. (författare) On The Noise And Power Performance Of A Shoe-Mounted Multi-Imu Inertial Positioning System 2017 Ingår i: 2017 international conference on indoor positioning and indoor navigation (ipin). - : IEEE. Konferensbidrag (refereegranskat)abstract Shoe-mounted inertial navigation systems, aka pedestrian dead reckoning or PDR sensors, are being preferred for pedestrian navigation because of the accuracy offered by them. Such shoe sensors are, for example, the obvious choice for real time location systems of first responders. The opensource platform OpenShoe has reported application of multiple IMUs in shoe-mounted PDR sensors to enhance noise performance. In this paper, we present an experimental study of the noise performance and the operating clocks based power consumption of multi-IMU platforms. The noise performances of a multi-IMU system with different combinations of IMUs are studied. It is observed that four-IMU system is best optimized for cost, area and power. Experiments with varying operating clocks frequency are performed on an in-house four-IMU shoe-mounted inertial navigation module (the Oblu module). Based on the outcome, power-optimized operating clock frequencies are obtained. Thus the overall study suggests that by selecting a well-designed operating point, a multi-IMU system can be made cost, size and power efficient without practically affecting its superior positioning performance.
34.	Carlsson, B, et al. (författare) A NOTCH FILTER BASED ON RECURSIVE LEAST-SQUARES MODELING 1994 Ingår i: Signal Processing. - : Elsevier BV. - 0165-1684 .- 1872-7557. ; 35:3, s. 231-239 Tidskriftsartikel (refereegranskat)abstract This paper presents a notch filter based on recursive least-squares sinusoidal modelling. This gives analytical insight both into least-squares modelling of sine waves in noise and the use of constrained notch filters. Especially, the derived filter corresponds to a commonly used notch filter with constrained poles and zeros.
35.	Carlsson, B., et al. (författare) Analysis and interpretation of a constrained notch filter 1992 Ingår i: Acoustics, Speech, and Signal Processing, 1992. ICASSP-92., 1992 IEEE International Conference on. ; , s. 293-296 Konferensbidrag (refereegranskat)abstract A notch filter based on discounted recursive least squares sinusoidal modeling is presented. This gives analytical insight both into least squares modeling of sine waves in noise and the use of constrained notch filters. Especially, it is shown that the discounted least squares solution converges to a commonly used notch filter with constrained poles and zeros, where the forgetting factor in the criterion corresponds to the pole radii in the filter. Also a Kalman filter interpretation is given for the derived constrained notch filter
36.	De Angelis, Alessio, et al. (författare) Indoor positioning by ultra wide band radio aided inertial navigation 2010 Ingår i: Metrology and Measurement Systems. - : Polish Academy of Sciences Chancellery. - 0860-8229. ; 17:3, s. 447-460 Tidskriftsartikel (refereegranskat)abstract A research study aimed at developing a novel indoor positioning system is presented. The realized system prototype uses sensor fusion techniques to combine information from two sources: an in-house developed local Ultra-Wideband (UWB) radio-based ranging system and an inertial navigation system (INS). The UWB system measures the distance between two transceivers by recording the round-trip-time (RTT) of UWB radio pulses. Its principle of operation is briefly described, together with the main design features. Furthermore, the main characteristics of the INS and of the Extended Kalman Filter information fusion approach are presented. Finally, selected static and dynamic test scenario experimental results are provided. In particular, the advantages of the proposed information fusion approach are further investigated by means of a high dynamic test scenario.
37.	Falk, Johan, et al. (författare) Direction Finding for Electronic Warfare Systems Using the Phase of the Cross Spectral Density 2002 Ingår i: RadioVetenskap och Kommunikation (RVK). ; , s. 264-268 Konferensbidrag (refereegranskat)abstract In modern electronic warfare systems there is a need for direction-ﬁnding of transmitters using waveforms for military stealth communication. In this paper, a correlation-based method is investigated utilizing the phase of the cross spectral density to estimate the time-diﬀerence-of-arrival from a two-channel digital receiver. A least squares method is reviewed, and its performance is investigated by theoretical analysisand by Monte-Carlo simulations. Proper Cramér-Raobounds are derived. It is shown that the method is statistically eﬃcient for ﬂat spectrum signals. The method is found to be a promising method for use against military communication in an electronic warfare direction-ﬁnding system.
38.	Falk, Johan, et al. (författare) Effects of frequency and phase error in electronic warfare TDOA direction-finding systems 2003 Ingår i: Military Communications Conference. - : IEEE conference proceedings. - 0780381408 ; , s. 118-123 Konferensbidrag (refereegranskat)abstract Electronic warfare systems for use against military communication sources include direction-finding. The considered direction-finding electronic-warfare system usestwo intercept receivers which is eavesdropping on thetransmitted signal with no knowledge of the waveformused, or its origin. Down-conversion to baseband is required in order to digitize the received signal. This canbe done using a superheterodyne receiver where an oscillator is used to mix the signal-of-interest to baseband.Errors in frequency and phase between the oscillatorsdegrade the performance. Because of this error, the per-formance derived in previous work by the authors willnot apply since the used model no longer is applicable.The extended model presented here considers the oscil-lator errors. The performance using the extended modelis determined numerically and the result is compared tothe Cramer-Rao lower bound for the ideal system usinga typical signal waveform.
39.	Falk, J., et al. (författare) Estimation of receiver frequency error in a TDOA-based direction-finding system 2004 Ingår i: Conference Record - Asilomar Conference on Signals, Systems and Computers. ; , s. 2079-2083 Konferensbidrag (refereegranskat)abstract Direction-finding of radio transmitters is considered and in particular correlation-based time-difference-of-arrival (TDOA) estimation between a pair of intercept receivers. In the target application, the received and down-converted signals are corrupted by a frequency error due to a receiver frequency tuning offset which degrades the performance of the TDOA estimation. Traditionally, the cross-ambiguity function (CAP) is used in a 2D scheme for joint TDOA and frequency error estimation. In this paper, sequential ID frequency error and TDOA estimators are introduced and compared to the 2D method. The 2D method attains the CRLB for both the TDOA and frequency error estimates, but have high computational and memory complexity. The proposed frequency error estimator is outperformed by the 2D method. However, the main objective is to estimate the TDOA and the proposed TDOA estimator have a performance similar to that of the 2D method. The main advantage of the proposed method is a reduction in both computational and memory complexity.
40.	Falk, Johan, et al. (författare) Multisource time delay estimation subject to receiver frequency errors 2003 Ingår i: CONFERENCE RECORD OF THE THIRTY-SEVENTH ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS & COMPUTERS, VOLS 1 AND 2. - 0780381041 ; , s. 1156-1160 Konferensbidrag (refereegranskat)abstract An electronic warfare (EW) system with two spatially separated intercept receivers, targeting military communication systems is considered. The EW system estimates the direct ion-of-arrival via a correlation-based time-difference-of-arrival (TDOA) method without any prior knowledge of the signals-of-interest. An important practical consideration is the oscillator frequencies of the two intercept receivers where a difference, or error, degrades the TDOA estimator performance. A measure of this degradation, or loss in power due to the frequency error, is derived and used to describe the robustness against receiver frequency errors. In the multisource scenario, time and frequency overlapping sources can be separated using direction-filtering of the cross-correlation function between the receiver outputs with good result if one signal at a time can be selected by the direction-filter. However, the performance of the considered estimator is degraded in a multisource scenario compared to the single source case.
41.	Fritzin, Jonas, et al. (författare) Phase Predistortion of a Class-D Outphasing RF Amplifier in 90 nm CMOS 2011 Ingår i: IEEE Transactions on Circuits and Systems - II - Express Briefs. - 1549-7747 .- 1558-3791. ; 58:10, s. 642-646 Tidskriftsartikel (refereegranskat)abstract This brief presents a behavioral model structure and a model-based phase-only predistortion method that are suitable for outphasing RF amplifiers. The predistortion method is based on a model of the amplifier with a constant gain factor and phase rotation for each outphasing signal, and a predistorter with phase rotation only. The method has been used for enhanced data rates for GSM evolution (EDGE) and wideband code-division multiple-access (WCDMA) signals applied to a Class-D outphasing RF amplifier with an on-chip transformer used for power combining in 90-nm CMOS. The measured peak power at 2 GHz was +10.3 dBm with a drain efficiency and power-added efficiency of 39% and 33%, respectively. For an EDGE 8 phase-shift-keying (8-PSK) signal with a phase error of 3 degrees between the two input outphasing signals, the measured power at 400 kHz offset was -65.9 dB with predistortion, compared with -53.5 dB without predistortion. For a WCDMA signal with the same phase error between the input signals, the measured adjacent channel leakage ratio at 5-MHz offset was -50.2 dBc with predistortion, compared with -38.0 dBc without predistortion.
42.	Host-Madsen, A., et al. (författare) Effects of sampling and quantization on single-tone frequency estimation 2000 Ingår i: IEEE Transactions on Signal Processing. - : Institute of Electrical and Electronics Engineers (IEEE). - 1053-587X .- 1941-0476. ; 48:3, s. 650-662 Tidskriftsartikel (refereegranskat)abstract The effects of sampling and quantization on frequency estimation for a single sinusoid are investigated. Cramer-Rao bound for I-bit quantization is derived and compared with the limit of infinite quantization. It is found that I-bit quantization gives a slightly worse performance, however, with a dramatic increase of variance at certain frequencies. This can be avoided by using four times ol oversampling. The effect of sampling when using nonideal antialiasing lowpass filters is therefore investigated through derivation of the Cramer-Rao lower bounds. Finally, fast estimators for 1-bit quantization, in particular, correlation-based estimators, are derived,and their performance is investigated. The paper is concluded with simulation results for fourtimes oversampled I-bit quantization.
43.	Host-Madsen, A., et al. (författare) The effect of sampling and quantization on frequency estimation 1998 Ingår i: 1998 IEEE International Conference on Acoustics, Speech and Signal Processing, ICASSP. ; , s. 2217-2220 Konferensbidrag (refereegranskat)abstract The effect of sampling and quantization on frequency estimation for a single sinusoid is investigated. The Cramer-Rao bound for 1 bit quantization is derived, and compared with the limit of infinite quantization. It is found that 1 bit quantization gives a slightly worse performance, however, with a dramatic increase of variance at certain frequencies. This can be avoided by using 4 times oversampling. The effect of sampling when using non-ideal antialiasing lowpass filters is therefore investigated. Cramer-Rao lower bounds are derived, and the optimal filters and sampling frequencies are found. Finally, fast estimators for 1 bit sampling, in particular correlation based estimators, are derived. The paper concludes with simulation results for 4 times oversampled 1 bit quantization
44.	Händel, Peter, 1962-, et al. (författare) A calibration scheme for imperfect quantizers 2000 Ingår i: IEEE Transactions on Instrumentation and Measurement. - : IEEE. - 0018-9456 .- 1557-9662. ; 49:5, s. 1063-1068 Tidskriftsartikel (refereegranskat)
45.	Händel, Peter, 1962-, et al. (författare) Adaptive estimation for periodic signal enhancement and tracking 1994 Ingår i: International journal of adaptive control and signal processing (Print). - : Wiley. - 0890-6327 .- 1099-1115. ; 8:5, s. 447-456 Tidskriftsartikel (refereegranskat)abstract A fast algorithm for enhancement and tracking of periodic signals with fixed or slowly varying central frequency in additive noise is proposed. The algorithm is based on results from discounted least squares identification of a harmonic signal model combined with a recursive update scheme for the estimated fundamental frequency. In particular the gain sequence of the algorithm is determined by the fundamental frequency and an eligible forgetting factor. The performance of the algorithm is compared with theoretical lower bounds and it is shown that the algorithm yields good results.
46.	Händel, Peter, 1962- (författare) Adaptive nonlinear modeling of periodic signals 1997 Ingår i: The First European Conference on Signal Analysis and Prediction, ECSAP-97, Prague, Czech Republic,24-27 June 1997. ; , s. 133-136 Konferensbidrag (refereegranskat)
47.	Händel, Peter, 1962-, et al. (författare) Adaptively calibrating analog-to-digital conversion with correction table indexing 2000 Patent (populärvet., debatt m.m.)abstract Methods, systems, and arrangements enable true wide-band calibration of analog-to-digital conversion (ADC) using correction table indexing (350, 660). The frequency of an analog input signal that corresponds to a digital output sample is accounted for, at least partially, when accessing a correction table (350, 660) during the creation and use thereof. For example, in addition to at least a portion of a current sample, at least portion(s) of previous and/or subsequent samples may be used to build (805) (e.g., by bit concatenation) an index for addressing a correction table memory. In effect, compensation may be achieved for ADC errors that are frequency dependent. This correction table (350; 660) indexing may advantageously be employed along with a scheme that estimates (1020A) one or more parameters of the analog input signal in the digital domain on a sample-by-sample basis in order to reconstruct the analog input signal in the digital domain.
48.	Händel, Peter, 1962- (författare) Amplitude estimation using IEEE-STD-1057 three-parameter sine wave fit : Statistical distribution, bias and variance 2010 Ingår i: Measurement. - : Elsevier BV. - 0263-2241 .- 1873-412X. ; 43:6, s. 766-770 Tidskriftsartikel (refereegranskat)abstract There has been a recent interest on the performance of amplitude estimation employing a coherently sampled sinusoidal model to noisy measurements. In [F. Correa Alegria, Bias of amplitude estimation using three-parameter sine fitting in the presence of additive noise, Measurement 42 (2009) 748-756.], several issues regarding the bias of the amplitude estimate were studied. In this work, the results are generalized to include a description of the distribution of the amplitude estimate, with explicit results on bias and variance as by-products. Simple closed form expressions for bias and variance are derived. It is shown that the amplitude estimate in finite samples obeys a Rician distribution. The biased amplitude estimator is also shown to beat all unbiased estimators in terms of mean square error, in a wide spread of scenarios.
49.	Händel, Peter, 1962-, et al. (författare) Analysis of a simple, effective frequency estimator based on Prony’s method 1998 Ingår i: Statistical Signal and Array Processing, 1998. Proceedings., Ninth IEEE SP Workshop on. ; , s. 316-319 Konferensbidrag (refereegranskat)abstract In a recent paper by Tufts and Fiore (1996) a low-complexity frequency estimator based on Prony’s method was proposed. The estimate is formed from two sample correlations r circ;(L1) and r circ;(L2), where 1 les;L1 les;L2 les;N-1 and N is the number of samples. For a correct phase unwrapping it is required that L1 and L2 are relatively prime. In this paper, a slight modification of the original algorithm is presented, and an expression for its asymptotic variance is derived. It is shown that the error variance is minimized for L1=3N/5 and L2=4N/5 for which the quotient of the error variance and the Cramer-Rao bound tends to 25/24 ap;1.042. Suboptimal settings of L1 and L2 are shown to exist, resulting in a lowered SNR-threshold while retaining the asymptotic efficiency. Simulation results which lend support to the theoretical findings are included
50.	Händel, Peter, 1962-, et al. (författare) Asymptotic noise gain of polynomial predictors 1997 Ingår i: Signal Processing. - 0165-1684 .- 1872-7557. ; 62:2, s. 247-250 Tidskriftsartikel (refereegranskat)abstract Finite impulse response filters for the prediction of polynomial signals are considered. An expression for the asymptotic noise gain (as the filter length increases without bound) is derived. It is shown that the asymptotic noise gain only depends on the polynomial order - in particular, it is independent of the prediction horizon. It is also shown that the noise gain forms a non-increasing sequence for increasing filter lengths. Numerical results that lend support to the theoretical findings are included.

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