Passive radar on moving platforms exploiting DVB-T transmitters of opportunity

The work, effort, and research put into passive radar for stationary receivers have shown significant developments and progress in recent years. The next challenge is mounting a passive radar on moving platforms for the purpose of target detection and ground imaging, e.g. for covert border control. A passive radar on a moving platform has many advantages and offers many benefits, however there is also a considerable drawback that has limited its application so far. Due to the movement the clutter returns are spread in Doppler and may overlap moving targets, which are then difficult to detect. While this problem is common for an active radar as well, with a passive radar a further problem arises: It is impossible to control the exploited time-varying waveform emitted from a telecommunication transmitter. A conventional processing approach is ineffective as the time-varying waveform leads to residuals all over the processed data. Therefore a dedicated clutter cancellation method, e.g. the displaced phase centre antenna (DPCA) approach, does not have the ability to completely remove the clutter, so that target detection is considerably limited. The aim must be therefore to overcome this limitation by exploiting a processing technique, which is able to remove these residuals in order to cope with the clutter returns thus making target detection feasible. The findings of this research and thesis show that a reciprocal filtering based stage is able to provide a time-invariant impulse response similar to the transmissions of an active radar. Due to this benefit it is possible to achieve an overall complete clutter removal together with a dedicated DPCA stage, so that moving target detection is considerably improved, making it possible in the first place. Based on mathematical analysis and on simulations it is proven, that by exploiting this processing in principle an infinite clutter cancellation can be achieved. This result shows that the reciprocal filter is an essential processing stage. Applications on real data acquired from two different measurement campaigns prove these results. By the proposed approach, the limiting factor (i.e. the time-varying waveform) for target detection is negotiated, and in principle any clutter cancellation technique known from active radar can be applied. Therefore this analysis and the results provide a substantial contribution to the passive radar research community and enables it to address the next questions

Comparison of Coal Face Bottom Dead Centre Solutions for the Effectiveness of Mining Operation - Coal Face Bottom Dead Centre 37 901 in Darkov Pit

Import 26/06/2013Bakalářská práce řeší zajišťování spodní úvratě porubů. Popisuje klasickou metodu pomocí individuální hydraulické výztuže a variantu vysokého kotvení. Porovnává rozdíly těchto dvou metod v oblasti bezpečnosti a efektivity práce. Řešena práce ukazuje fakt, že využitím svorníkování se značně urychlí a usnadní fyzicky namáhavá práce pracovníků rubání. Nasazením této efektivní technologie dochází jednak ke zvýšení postupu porubu, zvětšení manipulačního prostoru, tím zvýšení bezpečnosti a v neposlední řadě i zkrácením času přípravy spodní úvratě na překládku.This Bachelor´s thesis deals with the principle of the longwall bottom dead centre provision. The thesis focuses on a traditional method using individual hydraulic chocks and the high anchoring. The thesis compares the difference between these two methods in connection with safety and efficiency. As the results of the thesis show physically hard work done by mining workers is considerably faster and easier when using the technology called bolting. Using this effective technology leads to increasing coalface process as well as enlarging handling space, thereby increasing safety and shortening the time necessary to make ready a longwall bottom dead centre for reloading.Prezenční542 - Institut hornického inženýrství a bezpečnostivelmi dobř

Sposób konstruowania określeń europejskich akwenów morskich w językach niemieckim, szwedzkim i polskim

Recenzowany tom jest pokłosiem konferencji zorganizowanej w dniach 24–25 października przez Koło Naukowe Glottodydaktyków, działające przy Katedrze Lingwistyki Stosowanej i Kulturowej UŁ. Organizatorzy konferencji zaproponowali bardzo atrakcyjny i ważny temat, który zainspirował jej uczestników do przygotowania artykułów skupionych wokół trzech grup zagadnień: dydaktyki języka, lingwistyki kulturowej i dialektologii. Ogromnie cieszy zainteresowanie młodych naukowców tematyką dydaktyczną i glottodydaktyczną oraz kulturową. Zamieszczone w tomie artykuły pokazują poszukiwania nowych metod nauczania, przy znajomości dotychczasowych osiągnięć w tej dziedzinie, w oparciu o wiedzę językoznawczą i z wykorzystaniem technologii informacyjnych. Cykliczne organizowanie takich konferencji jest ważną i cenną inicjatywą młodych językoznawców, dydaktyków i kulturoznawców

A two-stage approach for direct signal and clutter cancellation in passive radar on moving platforms

This paper addresses the problem of direct signal interference (DSI) and clutter cancellation for passive radar systems on moving platforms using displaced phase centre antenna (DPCA) approach in the presence of receive channels imbalance. First, we show that using the signal emitted by the illuminator of opportunity as a source for channels calibration might be ineffective when DSI and clutter echoes have different directions of arrival. Then, a calibration approach is presented, based on supervised selection of clutter areas in the range-Doppler map. Finally, a two-stage strategy is presented, composed of an ECA-based DSI removal prior to DPCA clutter cancellation, which doesn’t require supervised selection of the calibration area. The effectiveness of this scheme in the joint suppression of DSI and clutter is shown against real data

TERMOELEKTRYCZNE URZĄDZENIE SOLARNE DO ZASILANIA PLATFORMY POMIAROWEJ

This work presents the prototype of the solar - thermoelectric device, which can float on water surface. It produces electrical energy as a result of the Seebeck effect in a commercial, low-cost Peltier module. The main application of the device will be an autonomous and a floating measurement platform. An important advantage of the presented solution is the possibility to work alike at day, when a solar light heats the surface of the absorber, and at night, when the different of temperatures between air and water causes the heat flux and in an effect the electricity. The device is capable of working for many cloudy days and also in winter on very short days. The presented device is based on low-cost and widely available components.W pracy zaprezentowano prototypowe solarne urządzenie termoelektryczne pływające po powierzchni wody. Wytwarza ono w niedrogim, komercyjnym module Peltiera energię elektryczną w wyniku zachodzącego w nim zjawiska Seebecka. Docelowo głównym obszarem aplikacyjnym urządzenia będzie zasilanie autonomicznej, pływającej platformy pomiarowa do monitorowania parametrów środowiskowych. Istotną zaletą przedstawionego rozwiązania jest możliwość pracy zarówno w dzień, gdy światło słoneczne ogrzewa powierzchnię absorbera, jak również w nocy, gdy różnica temperatur między powietrzem a wodą powoduje powstawanie strumienia ciepła w module Peltiera. Urządzenie może pracować przez wiele pochmurnych lub krótkich dni, także w zimie. Do konstrukcji układu zastosowano relatywnie tanie i łatwo dostępne w handlu komponenty

Passive radar DPCA schemes with adaptive channel calibration

This paper addresses the problem of direct signal interference (DSI) and clutter cancellation for passive radar systems on moving platforms employing displaced phase centre antenna (DPCA) approach. Attention is focused on the development of signal processing strategies able to compensate for the limitations deriving from amplitude and phase imbalances that affect the two channels employed on receive. First, we show that using the signal received from the illuminator of opportunity as a source for channels calibration might be ineffective when DSI and clutter echoes have different directions of arrival, due to the effect of angle-dependent channel imbalance. Then, a two-stage strategy is proposed, consisting of a preliminary DSI removal stage at each receive channel, followed by a clutter-based calibration approach that basically enables an effective DPCA clutter suppression. Different strategies for channel calibration are proposed, aimed at compensating for potential angle and range dependent channel errors, based on the maximization of the cancellation performance. Effectiveness of this scheme is shown against experimental data from a DVB-T based moving passive radar, in the presence of both real and synthetic moving targets

Underground radio communication systems

Omówiono wybrane systemy radiowe stosowane w zakładach górniczych, w tym przede wszystkim te, które wykorzystują propagację swobodną oraz kierunkową z przewodem promieniującym. Przedstawiono także systemy wykorzystujące standardy sieci WLAN w kopalniach.Described selected radio systems used in mining, including in particular those that use free propagation and directional one with leaky feeder cable. Also presented systems based on standard WLAN in the mines