Corner Reflector Antenna Design for Interference Mitigation between FM Broadcasting and Aeronautical Ground to Air Communication Radios

Third order intermodulation products caused by two or more FM broadcasting radios transmitter on a site to inter modulate either within transmitters themselves or within a non-linear component on site and those intermodulation products due to non-linearity’s of passive circuits of transmitters sharing same radiating element have been the source of interference in Tanzania to aeronautical ground to air communication (COM) systems which are safety services due to its nature of safeguarding human life and properties. These intermodulation products have been found in frequencies used by COM systems. This research work focused on using of corner reflector antenna to mitigate interference caused by FM broadcasting radio stations to COM facilities which are used for ground to air communication between control tower and pilots in Tanzania. Through simulations it is observed that the corner reflector antenna provide sufficient front to back ratio which facilitate in reducing electric signal strength and hence forth power level from FM broadcasting stations reaching the aeronautical facilities and hence mitigate the interference. Keywords: COM, FM, third order, intermodulatio

Review on Electromagnetic Interference and Compatibility in Aeronautical Radio communications Systems –Tanzania Case Study.

Electromagnetic interference (EMI) in communication systems is one of the major challenges which face the communication sector and is mainly caused by unwanted signals which can be characterized as noise. Due to this during communication system design stages, implementation phase and operation of communication link Electromagnetic compatibility (EMC) measures are of great importance. EMC analysis provides important information for communication system designers, planners and operators which facilitate coexistence of different communication systems.  In past few years there is an increase in number of Frequency Modulation (FM) broadcasting radio stations in Tanzania which operates in frequency band adjacent to aeronautical communication facilities. The FM broadcasting stations causes interference to the aeronautical radio-communication systems hence posing a great risk to aircraft navigation safety.  This is mainly due to unavailability of guard band between the two systems and high power radiated by FM broadcasting stations. This paper addresses interference cases in Tanzania and analyzes the interference mechanism for each interference case. To facilitate this field measurement was conducted in Arusha, Iringa and Zanzibar and mitigation measures which will ensure compatibility are proposed. In paper we have proposed the use of corner plate antenna to mitigate interference caused by FM broadcasting systems. Keywords: EMI, EMC, FM, Interferenc

GSM Network Optimization And Planning For Nelson Mandela African Institute Of Science And Technology

GSM network planning and optimization processes take in consideration a number of network parameters. In order to improve the network Key Performance Indicators (KPIs) are used as a guiding points. This paper has taken Nelson Mandela African Institute of Science and Technology as case study for network optimization. Index terms— MS- Mobile Station, TRX- Transmitter Receiver Unit, BTS- Base Transceiver System, BSC-Base Station Controller, KPI- Key Performance Indicators, QoS- Quality of Service, GFA- Ground Floor Wing A, FFA- First Floor Wing A

LASTEN OTSALOHKOLÄHTÖISTEN EPILEPSIOIDEN SEKÄ NREM-UNEN AIKANA ESIINTYVIEN PARASOMNIOIDEN EROTUSDIAGNOSTIIKKA

Tausta: NREM-unen aikaiset parasomniakohtaukset ja yölliset otsalohkoperäiset epilepsiakohtaukset ovat usein vaikeasti erotettavissa. Toisinaan diagnoosi on tarpeen varmistaa vähintään yhden vuorokauden kestävän video-EEG-rekisteröinnin avulla. Tässä tutkimuksessa on kartoitettu oireyhtymien erotusdiagnostiikan kannalta tärkeitä anamnestisia piirteitä. Lisäksi on paneuduttu oireyhtymien tyyppipiirteisiin ja kohtausoireiden eroavaisuuksiin muun muassa video-EEG-rekisteröintejä, kliinisiä kohtauskuvauksia ja sairaskertomuksia tarkastelemalla. Metodit: Tutkimusaineisto kerättiin ajanjaksona 01/1990–03/2008 TAYS:n lasten neurologian poliklinikalla otsalohkolähtöisten epilepsioiden vuoksi hoitoa saaneiden (n = 20) ja saman aikavälin NREM-unen parasomnioiden takia tutkittujen potilaiden (n = 13) sairauskertomuksista ja video-EEG-rekisteröinneistä. Tutkimus tehtiin retrospektiivisena, deskriptiivisena tutkimuksena. Tulokset: Sukuanamneesi oli positiivinen jokaisella parasomniakohtausoireita saavalla, jolta tieto löytyi. Yhdenkään parasomniapotilaan EEG-rekisteröinnistä ei havaittu poikkeavia löydöksiä. Jos kohtausoireita ilmaantuu sekä unessa että valveilla, on kyse todennäköisemmin epilepsiasta kuin parasomniasta. Jos kohtauksia esiintyy NREM-unen lisäksi myös REM-unen aikana, on kyseessä todennäköisemmin epilepsia kuin parasomnia. Parasmomniakohtauksissa motoristen oireiden laajuus on tyypillisesti maksimissaan alusta alkaen, kun taas epilepsiakohtauksessa liikelaajuus usein kasvaa kohtauksen edetessä. Sekä epilepsiapotilaiden että parasomniapotilaiden ryhmissä kohtausten kesto näyttäisi olevan sitä pidempi, mitä harvemmin kohtauksia esiintyy kuukauden aikana. Parasomnioihin liittyvä ääntely on usein itkua tai puhetta, kun taas epilepsiapotilaiden ääntely on useimmiten maiskuttelua tai örinää. Johtopäätökset: Tarkka ja oikein otettu anamneesi saattaa vähentää video-EEG-rekisteröintien tarpeellisuutta NREM-unenaikaisten parasomnioiden ja otsalohkolähtöisten epilepsioiden erotusdiagnostiikassa. Asiasanat:Yöllinen otsalohkoepilepsia, video-EEG-rekisteröinti, havahtumishäiriöt, uni-valvesiirtymän häiriö

Evaluating municipal websites: a methodological comparison of three think-aloud variants

Usability methods have received relatively little methodological attention within the field of E-Government. This paper aims to address this gap by reporting on a usability test of the municipal website of Deventer (the Netherlands), carried out by means of three variants of the think-aloud method (concurrent/retrospective think-aloud protocols and constructive interaction). These three methods had proved successful in a previous evaluation of a different municipal website, yet we decided to replicate our study in order to investigate whether the three methods would reveal different results when applied to another municipal website with a different information architecture. The results of our study showed that, as in the previous municipal website evaluation, the three evaluation methods were largely comparable in terms of output. Nevertheless, we did find a number of differences between the present and previous municipal website evaluation regarding the workings of the three methods—differences that could be explained by the different information architectures of the municipal websites tested. This suggests that the three evaluation methods might indeed work differently depending on the nature of the website that is being evaluated, and calls for more research into the effect of task type on the validity of evaluation methods