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.

Lidar for shallow underwater target detection

Abstract: Small underwater objects such as vehicles and divers can pose threats to fixed installations and ships. For ships, these threats are present both at sea and in harbors. Shallow underwater targets, including drifting mines, are difficult to detect with acoustic methods and thus complementary methods are required. If an airborne platform is available, some of those targets could be detected by passive optical means. However, for sensing from a ship or from land, optical detection can be highly improved by use of a pulsed laser system. We present simulated data of importance for the design of a lidar system with low incidence angle with respect to the water surface. We also present our first experimental data from underwater target detection with an incidence angle of 5 degrees.

Sensor models and localization algorithms for sensor networks based on received signal strength

Abstract: Received signal strength (RSS) can be used in sensor networks as a ranging measurement for positioning and localization applications. This contribution studies the realistic situation where neither the emitted power nor the power law decay exponent be assumed to be known. The application in mind is a rapidly deployed network consisting of a number of sensor nodes with low-bandwidth communication, each node measuring RSS of signals traveled through air (microphones) and ground (geophones). The first contribution concerns validation of a model in logarithmic scale, that is, linear in the unknown nuisance parameters (emitted power and power loss constant). The parameter variation is studied over time and space. The second contribution is a localization algorithm based on this model, where the separable least squares principle is applied to the non-linear least squares (NLS) cost function, after which a cost function of only the unknown position is obtained. Results from field trials are presented to illustrate the method, together with fundamental performance bounds. The ambition is to pave the way for sensor configuration design and more thorough performance evaluations as well as filtering and target tracking aspects.

A 60 GHz image rejection filter manufactured using a high resolution LTCC screen printing process

Abstract: An LTCC test panel including various mm-wave test circuits has been designed and manufactured using a recently developed screen printing process (Thales Microelectronics) having a highly optimised resolution, here evaluated using a minimum microstrip line width/gap of 2 mil (50.8 /spl mu/m). In this paper we report on a 60 GHz microstrip coupled lines bandpass filter manufactured on a 3.7 mil (94.0 /spl mu/m) thick Ferro A6S substrate using a minimum line gap of 2 mil. The electromagnetic effects caused by the top conductor recess were taken into account using direct full-wave simulations (Ansoft HFSS) but also by a circuit simulation methodology based on the use of effective relative permittivity and substrate height parameters. Preliminary measurement results show a 3 dB bandwidth of approximately 5 GHz, a passband insertion loss of 4 dB and a center frequency slightly above the simulated value. This bandpass filter could e.g. serve as an image rejection filter together with the 60 GHz WLAN chipset where it would demonstrate a 55 GHz image suppression of approximately 20 dB.