/library/oar/handle/123456789/127597 2025-11-09T22:43:14Z 2025-11-09T22:43:14Z /library/oar/handle/123456789/132375 2025-02-25T08:59:54Z 2024-01-01T00:00:00Z

Title: Design and fabrication of RF MEMS devices for wide-band VHF applications Abstract: This Ph.D. research work investigates the potential application of PiezoMUMPs technology to the design of a Lateral Bulk Acoustic Piezoelectric MUMPs (LBAW PiezoMUMPs) resonators that can operate in the VHF band. By analysing the effects of resonator size, number of electrode elements, and tether shape on parameters like resonant frequency and Quality factor (Qf). This work is based on analytical, Finite Element simulations, validated by prototype characterisation. Fine tuning through is essential in order to compensate for process related variation, for this reason thermal tuning using both ovenisation as well as on chip electrothermal tuning was investigated. Furthermore, volage tuning was also evaluated. Tuning via ovenisation achieved a tuning range of 300KHz over temperature range of 273 to 573K. Voltage tuning achieved a 30KHz over a range of 1 to 9 V. Electrothermal tuning resulted a 50KHz range for a thermal power of 50mW. This part of the study showed that thermal tuning results in a wider tuning range than voltage tuning. The study also investigates mechanical contact type RF-MEMS switches for VHF band applications, implemented on the same PiezoMUMPs process, in order to achieve a cost-effective wide frequency tuning. In this investigation, several electrostatically actuated switches, having different signal contact profiles were analytically studied and simulated using CoventorWare FEM software. These switches were optimized for different parameters depending on the design geometry and actuator comb fingers. Subsequently, different switch prototype configurations such as 1-way including the deep off option, as well as 2-way structures have been manufactured and characterised. Description: Ph.D.(Melit.)

2024-01-01T00:00:00Z /library/oar/handle/123456789/127769 2024-10-21T07:14:40Z 2024-01-01T00:00:00Z

Title: ASIC interface design for resonating micro-mirror MOEMS spectrometer Abstract: In recent years there has been an increased interest in air quality monitoring both at large scale and small scale. One useful tool to identifying different gases in the air is an IR absorption spectrometer. This device measures the attenuation of various spectral lines as an IR beam passes through a sample of the air in order to measure the concentration of individual gases. With the miniaturisation of air quality sensors, the move from benchtop spectrometers to micro-spectrometers is becoming more popular. A commonly-used approach for IR micro-spectrometers uses an IR detector array to determine the spectral response of an IR beam. However, increasing the spectral resolution of such a micro-spectrometer requires a proportional increase in the number of pixels in the detector, significantly increasing the fabrication costs of the detector. An alternative approach uses micro-mirrors in order to sweep a diffracted IR beam over a single IR sensor, where the spectral resolution does not depend on the number of pixels but on the accuracy of the micro-mirror angular position. For such an approach a precisely controlled micro-mirror with a known frequency and oscillation amplitude is needed. In this research an innovative closed loop controller for achieving such precision is presented. The controller has been developed by designing individual blocks which have been simulated and evaluated separately. The complete digital controller is then implemented on an FPGA for initial testing and then converted for implementation as an ASIC where the high voltage circuitry necessary to drive the electrostatically-actuated micro-mirror is also integrated, leading to a more compact implementation. The fabricated prototypes are then tested using an optical testbench. An analysis of the different waveforms that can be used to drive the micro-mirror and the ideal phase between the applied waveform and the micro-mirror angle is first carried out and used as a basis for the design of an all-digital closed loop controller. An improvement over previously published micro-mirror oscillation amplitude and phase measurement technique is then presented. This technique can be implemented in an all-digital controller since it relies on timing measurements from pulses generated by a single photodiode in the path of a reflected laser beam. An analysis is also carried out on different approaches that can be used to change the duty cycle of the drive waveform in order to change the amplitude of oscillation of the micro-mirror. The mentioned innovations are used to design an all-digital micro-mirror closed loop controller. The controller was simulated in MATLAB Simulink before implementation on an FPGA in order to verify its ability to control the micro-mirror. It is also demonstrated that the output signal of the controller can be synthesised using an adapted dithering-based fractional-N divider. The proposed controller is also implemented together with a high voltage output driver on the XFAB XT-018 BCD-on-SOI in order to demonstrate its feasibility of implementation in commercial applications. It is shown that the proposed controller is effective in accurately controlling the micro-mirror oscillation amplitude and thus validating the design. Description: Ph.D.(Melit.)

2024-01-01T00:00:00Z