Practical Harmonic Cancellation Techniques for the On-Chip Implementation of Sinusoidal Signal Generators for Mixed-Signal BIST Applications

International audienceHarmonic cancellation strategies have been recently presented as a promising solution for the efficient on-chip implementation of accurate sinusoidal signal generators. Classical harmonic cancellation techniques consist in combining a set of time-shifted and scaled versions of a periodical signal in such a way that some of the harmonic components of the resulting signal are cancelled. This signal manipulation strategy can be easily implemented using digital resources to provide a set of phase-shifted digital square-wave signals and a summing network for scaling and combining the phase- shifted square-waves. A critical aspect in the practical implementation of the harmonic cancellation technique is the stringent accuracy required for the scaling weight ratios between the different phase-shifted signals. Small variations between these weights due to mismatch and process variations will reduce the effectiveness of the technique and increase the magnitude of undesired harmonic components. In this work, different harmonic cancellation strategies are presented and analyzed with the goal of simplifying the practical on-chip implementation of the scaling weights. Statistical behavioral simulations are provided in order to demonstrate the feasibility of the proposed approach

Frequency and Pulse Generation Features in a Multifunctional Field Calibrator

The aim of the Thesis was to investigate improvements that could be made for frequency and pulse generation features of a next-generation multifunctional field calibrator as well as to suggests how the found improvements could be implemented. The improvement investigation was done by reviewing the frequency and pulse generation specifications of multifunctional calibrators that were on the market during the writing process of the Thesis. In addition to that, a customer needs analysis was performed by interviewing experts, and by analyzing customers’ feedback. Based on the results of the investigation, it can be concluded that the frequency and amplitude range and resolution of the current solution by Beamex is competitive and do not require alternation. However, the selection of generatable waveforms could be improved by adding a sine wave generation possibility into the frequency generation function. The current solution is only capable of generating symmetric and positive square waves. Furthermore, some requests for dual pulse generation were found during the investigation. The main focus in the solution design process was the sine wave generation because the dual pulse generation can be utilized easily if the next-generation multifunctional field calibrator has a modular structure. In that case, the number of frequency and pulse generation channels in the calibrator can be increased by adding multiple frequency and pulse generation modules into the calibrator. On the other hand, adding a sine wave generation option to the system is more complicated. Two possible solution suggestions for sine wave generation were designed and evaluated in the present thesis. One solution is based on direct digital synthesis and another one on usage of timer, registers, and direct memory access feature of a microcontroller. In theory, both of the solution suggestions should be able to generate square, pulse, and sine waves. However, by evaluating the solution suggestions, it can be said that the option to generate sine waves increases the complexity and cost of the system. In addition to that, the demand for sine wave generation might not be that high. Hence, it should be re-evaluated if it is profitable to add a sine wave option to the frequency generation