I takt med att ubåtarna blir allt tystare och svårare att detektera ställs allt högre krav på de sensorer som utvecklas för hålla jämna steg med denna utveckling. Redan under 80-talet kunde man konstatera att ubåtarna hade blivit så tysta att passiv detektering inte räckte till varför intresset istället riktades mot primärt aktiva system. Aktiv sändning medför sina egna nackdelar och tillsammans med de tekniker som utvecklats för att dämpa ekona från en ubåt gör att inte ens en aktiv, monostatisk sonar alltid ger tillfredsställande resultat. Till Försvarsmaktens nya medeltunga helikopter HKP14 har ett nytt sonarsystem införskaffats med möjlighet till fusionerad signalbehandling (s.k. multistatisk sonar) av signaler mottagna från flera olika mottagare såsom t.ex. sonarbojar.   Undersökningen syftar till att belysa vilka fördelar som kan erhållas vid helikopterbaserad, multistatisk ubåtsjakt och visar med ett antal räkneexempel bland annat att en större räckvidd och därmed även ett större detekteringsområde kan förväntas i en multistatisk konfiguration. Beräkningarna är gjorda med utgångspunkt i Uricks sonarekvationer men då faktorer såsom reverberation och kanalutbredning har avgränsats bort är det osäkert hur väl dessa resultat skulle stämma överens med en fältstudie. Utifrån de typfall som har undersökts visar emellertid studien på att de teoretiska fördelarna med ett multistatiskt system är tydliga och att dessa rent logiskt i viss utsträckning även borde gälla i praktiken. / The fact that submarines are becoming more silent and therefore harder to detect has led to an ever-increasing demand for more sensitive and sophisticated sensors to keep up with this development. As early as the 1980s it became obvious that submarines had become so silent that passive detection was not enough and the focus shifted toward active systems instead. Active transmission has its own disadvantages, and new techniques to silence submarines and reduce their acoustic signature even further have led to a situation where not even active, monostatic sonar always produces a satisfactory result. Along with the new medium sized helicopter (NH90), the Swedish Armed Forces have purchased a new sonar system that allows fused signal processing, using signals received by different receivers, such as sonobuoys. The aim of the study is to show what advantages can be gained from helicopter-based multistatic anti-submarine warfare and to show, by a number of arithmetic examples, that greater detection ranges and thus greater detection areas can be expected from a multistatic configuration. The examples are based on Urick’s sonar equations, but since factors such as reverberation and channel propagation of sound have been excluded from the study, it is uncertain how these results would compare to a field study. However, the study clearly shows the theoretical advantages of a multistatic system and that, on the basis of simple logic, these results should be feasible, to some extent, in practice.

This project revolves around a monostatic time of flight LiDAR, monostatic meaning that the emitted light and the incoming light are collocated and LiDAR being an acronym for light detection and ranging. The goal here is to explore and understand the principles of the LiDAR whilst also finding its advantages and shortcomings. One expected shortcoming is that of the effects of light scattering of the laser. To mitigate these effects a short laser pulse is desired without compromising on the power output. In order to reduce the pulse width the electronics of the LiDAR needed to be understood and two approaches emerged. The first revolved around simplifying the electronic schematics of the LiDAR to the point it could be described as a simple RLC-circuit and solving for the current analytically. The other approach was to simulate it using the simulation software LTspice. The results from the analytical approach and the LTspice simulation showed clear ways of how the pulse width could be decreased by altering the onboard resistance, inductance and capacitance. The easiest alternative was to simply reduce the capacitance, however this resulted in a lower power output. But these effects could be mitigated by simply increasing the applied voltage. However it was also discovered that the analytical and LTspice simulations were not entirely correct in their attempts to simulate the real behavior of the laser drive boards within the LiDAR. To study the effects of the scattering two theories were studied, namely Rayleigh and Mie scattering. The influence of Rayleigh scattering was quickly determined to be negligible but the Mie scattering results showed that it will definitely affect the LiDAR, even though the Mie scattering influence was extremely over exaggerated.