The FDTD method is a numerical method that uses the second-order central-difference method to discrete the Maxwell¡¦s equations in differential form, and positioning electromagnetic field in space grids and time grids. It is applied to analyze many electromagnetic problems in time domain. In the thesis, we applied FDTD methods to solve EMC/EMI problems like the interference to a mixer from an antenna, and the packaging effects to a small signal microwave amplifier and so on. Therefore, we applied equivalent current source approach to simulate each microwave elements at first. And, we extend the approach to field of EMC/EMI. researching the advantages of FDTD methods in Full-Wave analysis.

The research conducted in this dissertation studies the issues regarding the improvement of phase noise performance in a BiCMOS Silicon Germanium (SiGe) cross-coupled differential-pair voltage controlled oscillator (VCO) in a narrowband application as a result of a tail-current shaping technique. With this technique, low-frequency noise components are reduced by increasing the signal amplitude without consuming additional power, and its effect on overall phase noise performance is evaluated. The research investigates effects of the tail-current as a main contributor to phase noise, and also other effects that may influence the phase noise performance like inductor geometry and placement, transistor sizing, and the gain of the oscillator. The hypothesis is verified through design in a standard 0.35 μm BiCMOS process supplied by Austriamicrosystems (AMS). Several VCOs are fabricated on-chip to serve for a comparison and verify that the employment of tail-current shaping does improve phase noise performance. The results are then compared with mathematical models and simulated results, to confirm the hypothesis. Simulation results provided a 3.3 dBc/Hz improvement from -105.3 dBc/Hz to -108.6 dBc/Hz at a 1 MHz offset frequency from the 5 GHz carrier when employing tail-current shaping. The relatively small increase in VCO phase noise performance translates in higher modulation accuracy when used in a transceiver, therefore this increase can be regarded as significant. Parametric analysis provided an additional 1.8 dBc/Hz performance enhancement in phase noise that can be investigated in future works. The power consumption of the simulated VCO is around 6 mW and 4.1 mW for the measured prototype. The circuitry occupies 2.1 mm2 of die area. Copyright / Dissertation (MEng)--University of Pretoria, 2010. / Electrical, Electronic and Computer Engineering / unrestricted

This diploma work deals with active circuit elements and proposals of methods for measuring of some parameters of these elements. In the opening part the work deals with general classification of elements used in electronic circuits, ideal and real current sources and power supplies. Further there are stated basic parameters and characteristics presented by producers in a catalogue sheet for active elements MAX435, OPA660, AD844 and MAA741 element which already belongs to the history of IC. Main attention is paid to active circuit elements with current sources driven by CCCS (Current Controlled Current Source) and AD844 (high speed monolithic operational amplifier). In the work there is described a method for determining of selected parameters of active elements with CCCS. Examined parameters were frequency characteristics of current transfer, input impedance and output impedance. The proposed method was verified by a computer simulation on above mentioned active elements by means of PSpice software. Findings along with the description are summarized at the end of the work. In the closing part of the work there is undertaken a real measure of AD844 element based on the proposed method and the findings are compared with particular simulations. However, at first a flat connection board was made by means of EAGLE software and then the measure was performed on it.