| 1. |
- Berglund, Martin, 1985-, et al.
(författare)
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Evaluation of a microplasma source based on a stripline split-ring resonator
- 2013
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Ingår i: Plasma sources science & technology. - : Institute of Physics (IOP). - 0963-0252 .- 1361-6595. ; 22:5, s. 055017-
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a stripline split-ring resonator microwave-induced plasma source, aimed for integration in complex systems, is presented and compared with a traditional microstrip design. Devices based on the two designs are evaluated using a plasma breakdown test setup for measuring the power required to ignite plasmas at different pressures. Moreover, the radiation efficiency of the devices is investigated with a Wheeler cap, and their electromagnetic compatibility is investigated in a variable electrical environment emulating an application. Finally, the basic properties of the plasma in the two designs are investigated in terms of electron temperature, plasma potential and ion density. The study shows that, with a minor increase in plasma ignition power, the stripline design provides a more isolated and easy-to-integrate alternative to the conventional microstrip design. Moreover, the stripline devices showed a decreased antenna efficiency as compared with their microstrip counterparts, which is beneficial for plasma sources. Furthermore, the investigated stripline devices exhibited virtually no frequency shift in a varying electromagnetic environment, whereas the resonance frequency of their microstrip counterparts shifted up to 17.5%. With regard to the plasma parameters, the different designs showed only minor differences in electron temperature, whereas the ion density was higher with the stripline design.
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| 2. |
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| 3. |
- Grudén, Mathias, et al.
(författare)
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Design and Evaluation of Conformal Patch Antenna Array for Use with Wireless Sensor Network Inside Jet Engines
- 2013
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Ingår i: 2013 7th European Conference on Antennas and Propagation (EuCAP). - 9788890701818 - 9781467321877 ; , s. 2100-2102
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Konferensbidrag (refereegranskat)abstract
- The paper describes the design and simulation of an antenna that will be used in an extremely difficult environment, inside jet engines. The antenna enables wireless sensor network application in an environment that has never been tested before. Due to the extreme limitations, the antenna has to be ultra-thin, but still working. In the paper, the antenna is simulated and then measured in both anechoic and reverberation chamber. Simulated results agree well with the measured values. The radiation efficiency of the antenna is -13 dB and is not much affected when placed in metallic environment.
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| 6. |
- Grudén, Mathias, et al.
(författare)
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Field Operational Testing for Safety Improvement of Freight Trains using Wireless Monitoring by Sensor Network
- 2013
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Ingår i: IET Wireless Sensor Systems. - : Institution of Engineering and Technology (IET). - 2043-6386 .- 2043-6394.
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Tidskriftsartikel (refereegranskat)abstract
- Today, the majority of wagon failures on railroad systems are because of the poor maintenance of ball bearings, which causes emergent stops and delays. The existing stationary detectors, lack in predicting failures which cause troubles in scheduling maintenance. During the fall of 2011, a trial was performed by applying a wireless sensor network (WSN) aboard a train wagon with the objective to demonstrate a proof of concept for monitoring the temperature of ball bearings aboard the train wagon. This trial investigates several key aspects when applying sensor networks such as radio wave propagation, energy scavenging and performance of the WSN aboard the wagon. Two wireless links were used in the WSN. The aboard network communicates at 2.45 GHz, and the external communication is an 868 MHz radio frequency identification radio link. Since the energy in the WSN node is limited, appropriate energy scavenging devices are also presented and evaluated in a lab environment. Effort has been made to overcome these problems. The energy consumption in the network is still a problem; the most promising energy scavenging technique is piezoelectric harvesting by vibrations, which in the experiments scavenged 2.32 mW.
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| 7. |
- Gruden, Mathias, et al.
(författare)
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Large Ad Hoc Shielded Room with Removable Mode Stirrer for Mobile Phone Antenna Tests
- 2013
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Ingår i: IEEE transactions on electromagnetic compatibility (Print). - 0018-9375 .- 1558-187X. ; 55:1, s. 21-27
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Tidskriftsartikel (refereegranskat)abstract
- Reverberation chambers (RC) are widely used for measuring antenna performance and parameters for MIMO systems. RCs for mobile phone antenna tests are often specially designed for this purpose. The lowest frequency of operation of an RC is decided by its size. With a trend of lower frequency bands being allocated for mobile phones, the minimum size of RCs for mobile phone antenna tests increases, and is approaching the size of a normal room. At the same time, many large shielded rooms are already in use for various electrical measurements. In this paper, a standard shielded room designed for EMC testing is used as an RC for mobile phone antenna tests. To complete the RC, a large mode stirrer is built. The fact that the room is also used for other tests requires a detachable, foldable, and lightweight stirrer design. Therefore, metal meshes are evaluated for the design of the mode stirrer. The performance of the used room is verified by standard tests for RCs, and it is verified that it is possible to measure antennas from about 400 MHz up to 4 GHz with good accuracy. The size of the room also enables measurements including humans carrying mobile phones or body area networks.
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| 8. |
- Gruden, Mathias, et al.
(författare)
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Measurements and Simulations of Wave Propagation for Wireless Sensor Networks in Jet Engine Turbines
- 2011
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Ingår i: IEEE Antennas and Wireless Propagation Letters. - 1536-1225 .- 1548-5757. ; 10, s. 1139-1142
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Tidskriftsartikel (refereegranskat)abstract
- In this letter, measurements and simulations of wave propagation inside a jet engine fan have been performed. The investigation was done using both EM simulations of different cases of propagation inside the engine and by measuring the corresponding cases inside a half-scale model of a jet engine fan. The average path loss was calculated, and the shapes of the fading distributions were extracted. The time between two consecutive fading dips was measured in the empirical part. Measurements were performed with engine speeds of both 30 and 60 rpm and were shown to be linearly scalable from 60 rpm to full speed of 10 000 rpm. The results showed an average path loss of about 55 dB. When scaling the measurements from 60 rpm to full-speed rotation of about 10 000 rpm, the fading was so severe that the time slot between consecutive fading dips was limited to 290 mu s.
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| 9. |
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| 10. |
- Grudén, Mathias, 1985-
(författare)
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Wireless Sensor Network and Radio Wave Propagation in Harsh Environments
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This licentiate thesis cover two important subjects regarding the application of wireless sensor networks (WSNs). Both subjects are related to propagation mechanisms. The first subject is what the radio channel looks like and how it behaves. In this case three different, and extreme, environments are measured and characterized - a train, a half scale jet engine fan and a full scale military jet engine. The train environment is characterized by measure the path loss and fading over distance. For the case with the jet engines, difficulties were found to measure the path loss over distance, so in this case stationary antennas were used, but with the engine running. Each of these shows an extreme type of fading, also known as Rayleigh fading. For the case of jet engine at full speed (about 10 000 rpm), it was shown that the time between two consecutive fading dips where only 290 μs, which is about twice the length of a data package from the WSN involved in this project. The Rayleigh distributed amplitude fading occurs when there is a multipath environment, the radio waves propagate several different paths between the transmitter and receiver, which causes a superposition at the receiver. When having Rayleigh fading, the performance of the radio link is greatly reduced. When applying a WSN in this type of environment, the use of several antennas will improve the received power of the signal. This is done by adding extra antennas to a wireless system and in a clever way combine the signals, or select one of two signals from the antennas. In a book chapter and in a paper presented in the thesis, a new and low energy type of diversity is described. The performance of this new type of diversity is shown by having a two branch diversity and discretely shifting the phase of each branch before combining them. In this case, four relative phase shifts are performed during each symbol received. When performing a combining like this, the energy is saved by not having any decision circuitry. By using this type of diversity and using a 90 % signal reliability and an ideal environment, the diversity gain is 5.5 dB for an averaging detector and 10.3 dB for a peak detector. The drawback with this system is that it is only limited for systems using simple types of amplitude (ASK) or frequency (FSK) modulation.
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