Development of a composite CAD package to predict and reduce EM radiation from a PCB

A composite CAD package to predict and reduce radiation from a printed circuit board (PCB) is presented in this thesis. The composite CAD package is implemented using an electromagnetic (EM) computation tool linked with other circuit design packages (CDPs) such as ORCAD (a schematic design package), PSPICE (a circuit simulation package) and Boardmaker (a board layout tool). Software is developed to link all the packages so that one can incorporate EMC verification in the design process of an electronic product. The well-known Numerical Electromagnetic Code (NEC) version 2 is used as an EM computation tool. In using NEC-2 to predict PCB radiation, the PCB is simulated as a loaded thin wire structure just above (but not contacting) the surface of an imperfect ground. An algorithm is developed and implemented to automate the geometrical modelling of a wire structure for NEC-2. The data required by NEC-2 ( geometrical, load and electrical) for prediction of PCB radiation can be obtained from various CDPs. The development and implementation of data extraction algorithms are presented in this thesis. Single and double sided PCBs can be accommodated and the work can be extended to handle multilayer PCBs. The use of NEC-2 for this type of application has been validated experimentally and theoretically (by comparing NEC-2 predicted radiation with that obtained where the EM radiation from a pair of parallel PCB tracks running between two components/devices is computed using transmission line modelling-TLM). Both methods of evaluation are described in detail in this thesis and results showing good agreement are presented. TLM is employed by considering, (i) the effective dielectric constant of the medium (air and substrate) surrounding the PCB tracks and (ii) the displacement current between the two PCB tracks. The effect of displacement current in near field radiation is highlighted. The use of TLM for prediction of PCB radiation is verified experimentally. Measured radiation is in good agreement with prediction. In the developed composite CAD package, one can compare the predicted radiation with the mandatory EMC requirement laid down by the regulating bodies and "close the loop" to modify the design where these requirements have not been met. Various techniques to reduce radiation can also be employed. Reduction of radiation by providing shielding in some section of the circuit is proposed. An algorithm is developed and implemented to find the section of the circuit where shielding is necessary. The optimum layout (track separation to width ratio) that can minimise radiation is found theoretically. An optimum layout is also determined experimentally and compared with the theoretical value. A good agreement is found in this comparison. Thus a guideline to choose optimum layout for minimum radiation is provided

Development of a composite CAD package to predict and reduce EM radiation from a PCB

A composite CAD package to predict and reduce radiation from a printed circuit board (PCB) is presented in this thesis. The composite CAD package is implemented using an electromagnetic (EM) computation tool linked with other circuit design packages (CDPs) such as ORCAD (a schematic design package), PSPICE (a circuit simulation package) and Boardmaker (a board layout tool). Software is developed to link all the packages so that one can incorporate EMC verification in the design process of an electronic product. The well-known Numerical Electromagnetic Code (NEC) version 2 is used as an EM computation tool. In using NEC-2 to predict PCB radiation, the PCB is simulated as a loaded thin wire structure just above (but not contacting) the surface of an imperfect ground. An algorithm is developed and implemented to automate the geometrical modelling of a wire structure for NEC-2. The data required by NEC-2 ( geometrical, load and electrical) for prediction of PCB radiation can be obtained from various CDPs. The development and implementation of data extraction algorithms are presented in this thesis. Single and double sided PCBs can be accommodated and the work can be extended to handle multilayer PCBs. The use of NEC-2 for this type of application has been validated experimentally and theoretically (by comparing NEC-2 predicted radiation with that obtained where the EM radiation from a pair of parallel PCB tracks running between two components/devices is computed using transmission line modelling-TLM). Both methods of evaluation are described in detail in this thesis and results showing good agreement are presented. TLM is employed by considering, (i) the effective dielectric constant of the medium (air and substrate) surrounding the PCB tracks and (ii) the displacement current between the two PCB tracks. The effect of displacement current in near field radiation is highlighted. The use of TLM for prediction of PCB radiation is verified experimentally. Measured radiation is in good agreement with prediction. In the developed composite CAD package, one can compare the predicted radiation with the mandatory EMC requirement laid down by the regulating bodies and "close the loop" to modify the design where these requirements have not been met. Various techniques to reduce radiation can also be employed. Reduction of radiation by providing shielding in some section of the circuit is proposed. An algorithm is developed and implemented to find the section of the circuit where shielding is necessary. The optimum layout (track separation to width ratio) that can minimise radiation is found theoretically. An optimum layout is also determined experimentally and compared with the theoretical value. A good agreement is found in this comparison. Thus a guideline to choose optimum layout for minimum radiation is provided

Design of a high-speed, reconfigurable digital rank order filter

A new architecture to realize a modular, high speed, reconfigurable, digital Rank Order Filter (ROF) is presented in this paper. A bit-level algorithm by Kar and Pradhan has been modified in this work to implement the proposed ROF. Using the proposed digital rank selection circuit it is possible to find the element of a certain rank in a given sequence of N elements in each window in M steps, where M is the number of bits used in binary representation for the elements of the sequence. The size of the proposed ROF increases only linearly with the number of samples in each window to be ranked. The proposed ROF is also modular in nature, which means function of each part of the ROF is well defined and so the circuit can be easily expandable for larger window size. The proposed ROF has been implemented in FGPA and post-fit simulation results are presented in this paper. HSPICE simulation of the proposed ROF is also done for 0.18µm CMOS process

DECLARATION

We hereby declare that the thesis titled “Design and Development of Unmanned Aerial Vehicle (Drone) for Civil Applications ” is submitted to the Department of Electrical and Electronics Engineering of BRAC University in partial fulfillment of the Bachelor of Science in Electrical and Electronics Engineering. This is work was not submitted elsewhere for the award of any other degree or any other publication