Stefan Dickmann

Single Summation Expression for the Impedance of Rectangular PCB Power-Bus Structures Loaded With Multiple Lumped Elements

In this paper, a single summation expression is derived for the impedance of rectangular printed circuit board (PCB) power-bus structures populated with numerous lumped elements. This is based on a summation formula of a Fourier series, which has already been used to derive a fast summation algorithm for calculating the impedance of bare multilayer PCBs. The theoretical results obtained with the single summation agree well with the results of the common circuit theory. The single summation expression allows for a very fast and accurate impedance computation of populated PCBs

Damping of cavity-mode resonances in PCB power-bus structures using discrete capacitors

In this paper, the impact of lumped elements connected to the power-bus of high-speed printed circuit boards is investigated and a computationally efficient expression of the resulting input impedance is derived. This result builds the theoretical basis of a novel technique suppressing cavity-mode resonances within the power-bus using discrete capacitors. Guidelines for an optimized selection and placement of these capacitors are specified. The theoretical results are well confirmed by measurements.

Inductive and capacitive couplings in DC motors with built-in damping chokes

A quantitative analysis of parasitic coupling between elements of a 12 V DC motor and its damping chokes is presented. This analysis deals both with inductive couplings between several chokes as well as armature windings, and with capacitive couplings between chokes and the motor casing. It produces a motor model to take these effects into account. It is shown that while both types of coupling depend on the orientation of the chokes within the motor, inductive couplings do not have much effect on its high frequency impedance. The capacitance between choke and casing, however, can significantly influence the impedance of the motor in critical frequency ranges, such as the FM radio band

Improving the behavior of PCB power-bus structures by an appropriate segmentation

An effective and cost efficient method for suppressing cavity mode resonances within the power-bus of high-speed printed circuit boards is presented. It is shown that resonant modes can be completely suppressed by segmenting the power-bus into rectangular parts of smaller dimensions and connecting these parts suitably. For the case of identically shaped segments a double summation expression of the resulting voltage distribution within each part is derived. Furthermore, the impact of different connections between the segments is investigated. The theoretical results are well confirmed by measurements.

Determination of mode conversion on differential lines

This paper describes the problems of mode conversion on differential lines. For the determination of mode conversion between the common mode and the differential mode two possibilities are suggested. The first method is the use of modal impedance matrices Zmacrm to analyse the conversion related to current and voltage. The second method uses the S-parameters to calculate the mixed mode parameters to determine the conversion of modal power waves. Both views on the conversion of modes will be combined to alter the view on the problem.

Electromagnetic interference coupling into cardiac pacemaker electrodes

Cardiac pacemakers (PMKs) are vital for many persons sufferering from heart diseases, and a malfunction of those devices can have terrible consequences for their wearers. The main source of malfunctions is the PMKs electrode which acts linke an antenna. An incident electromagnetic field can couple into the electrode and cause an interference voltage at the PMKs input connector. This signal can be misinterpreted as the electrocardiogram (ECG) of the heart and mislead the PMK to wrong reactions. This paper presents the results of series simulations for calculating the maximum input voltage as a function of the electical field strength of a plane wave penetrating the human body.

SPICE simulation method for BCI component tests

This paper presents a virtual immunity test method using SPICE. This method facilitates EMC-compliant eletronic design. As an example, it is used to virtualize the BCI test method. It can also be applied to e.g. the stripline method. The required SPICE models of the components of the measurement setup are generated just once. They are based on scattering parameter measurements. These measurements are made with real RF components of the BCI test setup. In a schematic the SPICE models and the test circuit are connected according to the real test setup. At first in an AC analysis all voltages and currents are simulated by modelling the BCI clamp as an AC source with a constant stimulus of one volt. During real measurements a control computer sets the frequency-dependent amplitude of the generator. For this process, the standard DIN ISO 11452:4 specifies two test conditions: “open loop” and “closed loop”. In the virtual immunity test, all simulated voltages and currents due to the one volt stimulus are linearly scaled in order to match the real conditions using a computer-controlled frequency-dependent RF test power. This virtual test method makes the development process faster and cheaper.

Fuel Cell System Optimization Using Bypass Converters

The reduction of CO2 emissions, and therefore the increase of ecoefficiency, is one of the most important challenges for the aircraft industry. An approach could be the more electric aircraft concept. Within this concept, the traditional auxiliary power unit could be replaced by a multifunctional fuel cell system. For integration into the ±270 Vdc grid, it is necessary to convert the load-dependent fuel cell output voltage using a direct current-to-direct current converter. The converter usually is designed for the maximum available fuel cell power. This paper deals with an adaption of the fuel cell output voltage to achieve downsizing of the converter. The proposed converter structure with an additional bypass has weight-saving effects and improves overall system efficiency.

Automatic HF model generation and impedance optimization for low voltage DC motors

This paper presents a high frequency (HF) generic electrical model for low voltage DC motors. A software model generator creates an electrical circuit which reproduces the high frequency impedance Z of any common DC motor within a frequency range from 150 kHz to 1 GHz. Z is calculated only from construction and material parameters, like e.g. armature geometry and winding wire radius. With this model, it is possible to perform sensitivity analyses of motor construction parameters and optimize its design by finding parameters which best match a desired impedance curve. This can help finding a motor design with lower conducted electromagnetic interference (EMI).

EMC modelling of cardiac pacemakers

Cardiac pacemakers are vital for many persons sufferering from heart diseases, and a malfunction of those devices can have terrible consequences for their wearers. Yet, in a signal environment evermore complex, the influence of external signals interfering with the normal operation of a pacemaker is getting stronger. We present an analytical linear model for a pacemaker and use it for a detailed investigation on the influences of external signals on the operation. In a second step, we take into account non-linear properties and investigate the most common signal types using the non-linear model.