Design of an Optimal Analogue Microphone System for Best Possible Capture of Incoming Acoustic Signals

This project examines how to achieve the best possible capture of incoming acoustic signals in a surveillance camera without overspending. This will be done by designing a complete analogue microphone system to be integrated into a surveillance camera and identify the critical stages in terms of performance. The project will cover the complete analogue signal chain from incoming acoustic signals to analogue-to-digital conversion which covers the following steps: Evaluation of mechanical designs to eliminate undesired acoustic effects, choice of an optimal microphone, design of analogue signal processing such as amplification, filtering and signal level adjustments, evaluation of an optimal signal path for minimal interference and evaluation of an analogue-to-digital converter. A complete microphone system has been successfully implemented with the desired performance in terms of frequency response, distortion, noise and dynamic range. This has been done by identifying the limiting factors and adapting the performance of the surrounding components accordingly.In this project the complete analogue signal chain from incoming acoustic signals to analogue-to-digital conversion is implemented and evaluated. This covers the mechanical design, choice of microphone and OP-amplifiers, power supply voltage regulation and analogue signal processing including amplifier, filters, line driver and attenuator. Each stage is tested separately, and finally, the complete microphone system implementation is tested and evaluated. The measurements show an outstanding SNR which makes it possible to detect sounds from very far away, the THD is well below 1 %, which can be considered inaudible, and the frequency response is flat for low frequencies and has a peak for high frequencies which may be desired when listening to sounds far away since high frequencies are more easily attenuated