Swedish Defence Research Agency

About: Swedish Defence Research Agency is a government organization based out in Stockholm, Sweden. It is known for research contribution in the topics: Radar & Synthetic aperture radar. The organization has 1413 authors who have published 2731 publications receiving 56083 citations. The organization is also known as: Totalförsvarets forskningsinstitut.

Noise radar using random phase and frequency modulation

Abstract: Pulse compression radar is used in a great number of radar applications. Excellent range resolution and high ECCM performance can be achieved by wide-band modulated long pulses, which spread out the transmitted energy in frequency and time. By using random noise as waveform, the range ambiguity can be suppressed as well. The same limit in Doppler resolution is achieved as for a coherent Doppler radar when the time compression of the reference is tuned to that of the target. Mostly, the random signal is transmitted directly from a noise generating HF-source. A sine wave, which is phase or frequency modulated by random noise, is an alternative giving similar performance but higher transmitted mean power when peak-limited transmitters are applied. A narrower modulation noise bandwidth can also be applied to generate the same output bandwidth. For phase modulation, the bandwidth amplifying factor is simply the rms value of the phase modulation, and for a frequency modulating waveform, the output rms bandwidth equals the rms-value of the frequency modulation. The results also show that the range sidelobes can be highly suppressed compared with the sidelobes of the modulating signal. The mean and variance of the correlation integral are derived in terms of the autocorrelation function of the modulation. The combined effects of low range sidelobes and enhanced range resolution make frequency and phase modulation attractive.

Radioxenon background at high northern latitudes

Abstract: [1] As part of the International Noble Gas Experiment (INGE) two stations were deployed in remote regions at high northern latitudes: Longyearbyen, Spitsbergen, Norway (78.2°N), and Yellowknife, Canada (62.5°N). With one exception, both stations are 2000 km or more from any single known stationary nuclear facility. Nevertheless, the short-lived anthropogenic radionuclide = 5.24 days) has been detected on a regular basis at both stations, and also = 11.84 days) was found at the Yellowknife station. Measuring these very low concentrations (∼0.1 mBq/m3) has been possible because of the introduction of new and sensitive equipment developed specifically for the verification of the Comprehensive Nuclear-Test Ban Treaty. By means of atmospheric transport modeling, it was determined that the measurements at both sites are broadly consistent with reported releases from reactors in North America and Europe and that the Spitsbergen station is much more susceptible to this influence than the Yellowknife station. Especially at Spitsbergen, the simplified assumption of a continuous bulk release across Europe could well explain the month-to-month variation of the time series. A future radioxenon event classification scheme for treaty verification purposes thus needs to consider the actual meteorological situation and large-scale transport processes.

An ontology controlled data fusion process for a query language

Abstract: Query languages designed for acquisition of data from multiple sensor data sources where the data generally are of heterogeneous type requires a number of internal functionality that is not available in traditional query languages. The required functionality can, for instance, be a method for multi-sensor data fusion, methods for query optimization and refinement. A further required technique relates to the problem of selecting sensors that eflciently can respond to the various queries without laying the responsibility of the sensor management on the users. The approach taken in this work has been to introduce an ontological knowledge-based system that can support selection of both sensors and object recognition algorithms as well as the control of the sensor data fusion process.

Basic characterization of 233U: Determination of age and 232U content using sector field ICP-MS, gamma spectrometry and alpha spectrometry

Abstract: The possibility to determine the age, ie the time since the last chemical separation, of 233U was studied using two fundamentally different measurement techniques: inductively coupled plasma mass spectrometry (ICP-MS) and gamma spectrometry Moreover, the isotope ratio 232U/233U was measured using both alpha spectrometry and gamma spectrometry For the two materials analysed, all measurement results were in agreement, ie consistent within the combined uncertainties One of the materials was also measured using gamma spectrometry under field conditions This measurement was also in agreement with the other results on this material

A wideband, wide angle scan, microstrip array antenna element

Abstract: In this paper, we present a very broadband array antenna element (7.5-17 GHz) consisting of aperture coupled stacked microstrip antenna elements. Theoretical results for an infinite array, as well as theoretical and experimental results for a 2-element waveguide simulator are presented. The agreement between the theoretical and the experimental results for the waveguide simulator is good. The obtained results indicate the possibility of achieving bandwidths exceeding an octave, while maintaining widescan capabilities, for large arrays of microstrip antenna elements.