This work presents a distance measurement system for the localization of passengers in the sea in case of a ship sinking emergency. By applying the radar principle together with a switched injection-locked oscillator (SILO) as an active reflector the distance to a passenger can be determined through continuous measurement of the roundtrip time of flight of a chirp signal. The system is based on a concept previously published in [Wie03, VG08, Str14] and for the first time is designed in the 2,45GHz ISM frequency band.
Criteria for the design of SILOs formulated in [Str14] were applied and verified for the first time at an operating frequency of 2,45GHz. The designed circuits were manufactured in a SiGe BiCMOS technology. The SILOs are based on a commonbase Colpitts and cross-coupled topology and exhibit the lowest published input referred noise power of −79 dBm. The output power is 12,3 dBm and 12,6 dBm, respectively. The efficiency of the cross-coupled as well as Common-Base Colpitts SILO is 26%.
The theory of a SILO was extended towards the influence of interfering signals and the modulation signal. An interfering signal influences the starting behavior of a SILO in a way that a distance measurement leads to incorrect results. It was shown that interfering signals in the ISM frequency bands of 868MHz, 2,4GHz and 5,8GHz don’t allow correct distance measurements due to their high output power. Therefore, it is recommended to use an operating frequency of the SILO that is not close to any possible interfering signal, like the ISM band at 24GHz. This minimizes measurement errors and enables a more accurate distance measurement. Furthermore, it was shown that a phase coherent start of oscillation to any received signal is influenced by the modulation signal. For injection powers below −40 dBm the oscillator does not start its oscillation due to the injected signal, but to the modulation signal itself. This disables exact distance measurements.
Through the use of a modulation capacitor at the base of the tail current source this effect can be minimized and the input referred noise power of the oscillator can be improved. The functionality of the distance measurement system was also verified for both SILO topologies. The range of the system in the best case scenario with a Common-Base Colpitts SILO was 120m, at an accuracy of 53 cm and a precision of 42 cm. All results regarding accuracy and precision exceed the specification of the system.
|04 March 2016
|Ellinger, Frank, Ußmüller, Thomas, Technische Universität Dresden
|Hochschulschriftenserver (HSSS) der SLUB Dresden
|doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text
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