Seminar: Integrated Circuit Design for Fluxgate Magnetometers
Fluxgate magnetometers are the most widely used sensors for space applications, particularly for planetary missions. This statement is supported by the large number of space missions over the past few decades that have investigated the diversity of planetary and inter-planetary magnetic properties. However, to achieve highly linear and accurate measurements, a dedicated front-end electronic circuit is essential to read out the magnetic field information. It typically consists of a forward-path that demodulates and filters the output signal of the fluxgate sensor and converts it into the digital domain using an analog-todigital converter. To improve the linearity and stability of the measurement, digital signal processing is used to provide a feedback signal via a feedback path, effectively cancelling the ambient magnetic field within the fluxgate sensor. Nevertheless, most space-qualified front-end implementations reported in the literature are built using a mix of discrete and integrated components, often combined with an FPGA for digital signal processing, and are therefore limited in the performance that can be achieved. In addition, space electronics must be lightweight, compact and power-efficient, while withstanding extreme environmental conditions such as temperature fluctuations and ionizing radiation, to enable the feasibility and cost-effectiveness of space missions. These requirements can be met by the use of integrated circuits. Consequently, this thesis evolves along the design and on-chip implementation of important elements of the next generation fluxgate magnetometer frontend. Therefore, based on a review of the current state of the art of fluxgate magnetometer measurement systems, novel concepts and circuits that can be integrated on-chip have been developed. As a result, a digitally-controlled current source for the feedback path was proposed and implemented, capable of providing low noise, high precision currents over a defined frequency range to cancel the ambient magnetic field within the sensor. In addition, it should be stressed that the advantage of the developed digitally-controlled current source is its minimal power consumption while remaining linear at high field amplitudes. Furthermore, a new concept was suggested to efficiently read out the magnetic field information by applying the principle of N-path filtering to an analog lock-in amplifier. In addition, the research in this thesis can be applied to challenges related to other sensor interfaces, as the solutions presented are not limited to fluxgate sensor front-ends. In conclusion, to demonstrate the performance of the developed integrated circuit blocks, experimental results of the manufactured circuit prototypes are used to manifest the knowledge provided.
recording: www.youtube.com/watch