Due to the tendency of faster data rates and lower power supply voltage in the integrated circuit (IC) design, Simultaneously Switching Noise (SSN) and ground bounce become serious concerns for designers and testers. This noise can be a source of electromagnetic interference (EMI). It propagates through the power/ground planes on the printed circuit board (PCB) and it can couple to the nearby circuit affecting the performance of other devices. This noise results in antenna currents into connected cables and it can also increase the edge radiation from the PCB. In mixed signal systems it leads to sensitivity degradation or radiofrequency (RF) interference issues of radio-frequency circuits. This research work is focused on how to mitigate noise and reduce EMI by means of structuring the power plane of a PCB with Electromagnetic Band Gap (EBG) structures. A novel concept for ultra-wide-bandwidth suppression of SSN is proposed and implemented. This method consists of applying EBG cells with different stop bands creating noise isolation over a wide frequency region. The thesis starts with a general description of Power Distribution Network (PDN) of a PCB. It discusses the main challenges modern PCB designers are facing. Power and ground planes which are symmetric in shape and size create a resonating waveguide structure, an ideal path for SSN propagation. The mechanism of noise generation and propagation through the PDN and general approach of PDN noise reduction is discussed. Typically used methods include placement of EMI passives such as decoupling capacitors and ferrite beads and via stitching. The drawback of these methods is the limited frequency bandwidth they can cover, and the need to integrate additional components. Reduction of SSN noise by means of EBG was intensively studied over the last decades. However, most of the structures are effective only in a limited frequency band. Often they are embedded in a PCB as a separate layer or require extra vias which increase the manufacturing cost. In this work a new type of planar EBG structures was proposed as a means to avoid the generation and propagation of common-mode currents due to SSN in the power plane of PCBs, and thereby reducing their radiated emissions. The EBG also have beneficial effects on the differential-mode noise in PDN due to the SSN. To guide the design of EBGs for SSN reduction, several modelling techniques of the EBG structures based on results achieved with full-wave electromagnetic simulations by means of CST Microwave Studio and transmission matrix analysis are used. The dispersion diagram of the proposed EBG structure is validated by insertion loss measurements of the prototype boards. It was shown that a power plane structure is needed only locally for circuitry decoupling by creating a low impedance current path. The effect of different PDN designs such as power plane, power track and 2 single-cell EBG structures and different sized cells EBG on the noise reduction in PCB with active components was investigated. Some high permittivity materials were implemented as a PCB substrate to create a large power-ground plane capacitance, and its effectiveness to reduce EMI was investigated. Many researchers have investigated the effect of EBG using passive elements only. In this thesis not only the passive elements behaviour is discussed, but a design with active components was used too. The reduction in radiated electromagnetic fields and common mode currents of PCB with active components and various PDNs was studied. An equivalent circuit of active boards with a PDN was created with a SPICE circuit simulator. The proposed new EBG structure behaves as a wideband low pass filter reducing EMI. The key result of the work presented in this thesis is that by applying EBG structured power plane and supporting each individual electronic module on the board by its own power patch interconnected by - relatively- thin traces, instead of standard power ground plane couples which are identical and parallel to each other, can reduce SSN, common mode noise and radiated emission of the PCB.
|Award date||18 Nov 2015|
|Place of Publication||Enschede|
|Publication status||Published - 18 Nov 2015|