| 1. |
- Falk, Johan, et al.
(författare)
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Direction Finding for Electronic Warfare Systems Using the Phase of the Cross Spectral Density
- 2002
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Ingår i: RadioVetenskap och Kommunikation (RVK). ; , s. 264-268
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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.
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| 2. |
- Falk, Johan, et al.
(författare)
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Effects of frequency and phase error in electronic warfare TDOA direction-finding systems
- 2003
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Ingår i: Military Communications Conference. - : IEEE conference proceedings. - 0780381408 ; , s. 118-123
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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.
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| 3. |
- Falk, Johan, et al.
(författare)
-
Multisource time delay estimation subject to receiver frequency errors
- 2003
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Ingår i: CONFERENCE RECORD OF THE THIRTY-SEVENTH ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS & COMPUTERS, VOLS 1 AND 2. - 0780381041 ; , s. 1156-1160
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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.
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| 4. |
- Jansson, Johan, et al.
(författare)
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Model based control and optimization in pulpindustry
- 2004
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Ingår i: Proceedings of SIMS 2004. - 8774753169 ; , s. 103-110
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Konferensbidrag (refereegranskat)abstract
- In this paper we present a combination of the usage of a model for the whole mill on-line simulation and more advanced models for specific process sections for control systems and online diagnostics. Different solution methods are described together with where the different approaches are best suited.
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| 5. |
- Jansson, Johan
(författare)
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The Formation of Hidden Information : The Geography of the Swedish Internet Industry
- 2004
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Konferensbidrag (populärvet., debatt m.m.)abstract
- Taking off from the burst of the Internet bubble and the ideas of the new technology as a space shrinking development this paper deals with the Internet industry in Stockholm, Sweden, and the question of agglomeration of economic of activities. Through a theoretical framework of localized and tacit knowledge, this paper discusses the importance of proximity, especially in the sense of knowledge transmission. The paper is structured in three main sections. First, a discussion of the benefits of being located in an agglomeration of firms is introduced, and connected to this some important ideas coming out of the literature on localized learning and tacit knowledge are being reviewed. Second, to give a short introduction to the Swedish Internet industry and the agglomeration of Internet firms in Stockholm. Finally, the paper will analyse empirical findings from a interview survey in the Stockholm Internet agglomeration from such a theoretical framework. The empirical findings suggests that firms within the Internet industry are located in close proximity to each other because of the importance of dense informal interpersonal networks, that facilitate the search for both new customers and collaborators. The findings also stress the importance of proximity in creating these dense networks.
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| 6. |
- Jansson, Patrik, 1972, et al.
(författare)
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A Framework for Polytypic Programming on Terms, with an Application to Rewriting
- 2000
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Ingår i: Workshop on Generic Programming.
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Konferensbidrag (refereegranskat)abstract
- Rewriting is a typical example of a polytypic function. Given any value of a datatype (an algebra of terms), and rules to rewrite values of that datatype, we want a function that rewrites the value to normal form if the value is normalizable. This paper develops a polytypic rewriting function that uses the parallel innermost rewriting strategy. It improves upon our earlier work on polytypic rewriting in two fundamental ways. Firstly, the rewriting function uses a term interface that hides the polytypic part from the rest of the program. The term interface is a framework for polytypic programming on terms. This implies that the rewriting function is independent of the particular implementation of polytypism. We give several functions and laws on terms, which simplify calculating with programs. Secondly, the rewriting function is developed together with a correctness proof. We just present the result of the correctness proof, the proof itself is published elsewhere.
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| 7. |
- Nordlund, Per-Johan, et al.
(författare)
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A Framework for Particle Filtering for Positioning, Navigation and Tracking
- 2001
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Ingår i: Proceedings of the 11th IEEE Signal Processing Workshop on Statistical Signal Processing. - : IEEE. - 0780370112 ; , s. 34-37
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Konferensbidrag (refereegranskat)abstract
- A framework for positioning, navigation and tracking problems using particle filters (recursive Monte Carlo methods) is developed. Automotive and airborne applications, approached in this framework, have proven a numerical advantage over classical Kalman filter based algorithms. Here the use of non-linear measurement models and non-Gaussian measurement noise is the main explanation for the improvement in accuracy, and models for relevant sensors are surveyed.
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