In this report, the design of a subsystem within a localization system for the Bosch DICENTIS wireless conference system will be presented. The localization system will function by means of using acoustic Time Difference Of Arrival (TDOA) measurements to determine the location of each unit connected to the DICENTIS conference system. By unit, the system on the desk of each attendee in the conference, that contains a microphone and speaker is meant. The task of the subsystem presented is to estimate propagation times of transmitted signals between speakers of each unit in the conference system and the microphones of each unit. The design choice for the type of localization method implemented is based on the gathered information from an initial literature study, the hardware specifications of the Bosch DICENTIS system and the demands for the localization system that were imposed by Bosch. The subsystem will function by transmitting a set of pseudo-random codes, modulated using a type of Frequency Shift Keying (FSK), where two On Off Keying (OOK) signals, modulated at different frequencies, are superimposed. The received and demodulated pseudo-random codes are then correlated with multiple different peak detectors that will correlate with multiple different sets of the transmitted string of pseudo-random codes to gain a higher robustness for the estimated propagation times and a higher accuracy for these estimates. Results show that the the use of multiple different sets of transmitted codes indeed improves the propagation time estimation. The overall system as presented, concerning accuracy and robustness, meets the requirements made by Bosch. However, in future work, optimalization of the system with regard to computation time is required.

Class-D amplifiers are widely used in audio applications that require a high power efficiency. A high PSRR is beneficial when the power supply contains significant audio band content. Due to mismatches present in the feedback, these can dominate the PSRR of the class-D amplifier, provided the amplifier has sufficient loop gain. No literature has been found that describes a solution to improving the PSRR and CMRR across the full audio band. This work proposes chopping of the input and feedback resistors in a class-D to address this issue. With this technique's application, a >100dB PSRR and CMRR across the audio band is achieved.