https://www.um.edu.mt/library/oar/handle/123456789/2069 2026-04-04T03:44:12Z 2026-04-04T03:44:12Z https://www.um.edu.mt/library/oar/handle/123456789/144078 2026-02-24T14:19:49Z 2025-01-01T00:00:00Z

Title: Adoption of the LoRa transmission protocol for a low power indoor air quality monitoring system Abstract: Indoor air quality (IAQ) is a critical, often-overlooked public health concern, driving the need for robust Internet of Things (IoT) monitoring systems to optimise building ventilation and energy efficiency. This research addresses two major gaps: the high power consumption of existing wireless sensor nodes and the lack of cost-effective, scalable big data systems for large-scale IAQ monitoring. The core contribution is an ultra-low-power, low-cost wireless sensor node integrating state-of-the-art (SOA) sensors for carbon dioxide, volatile organic compounds, particulate matter, temperature, humidity, and pressure. Utilising dynamic power management, a sleep mode current draw of 270 nA and an average active current of 38 mA is achieved. This translates to an overall energy consumption of approximately 327 μAh per hour, and a projected battery life of 40 months on a 10,500 mAh battery. The achieved power efficiency is significantly better than both comparable academic and commercial SOA devices, even while offering a broader range of sensing capabilities. Complementary to this, the work introduces a cost-effective, LoRa-based big data system for large-scale IAQ monitoring. This system features a novel data forwarding server that calculates Air Quality Index (AQI) and Thermal Comfort Index (TCI) values, storing the enriched data in a document-oriented database. The research also validated a theoretical simulation model for indoor LoRa propagation. Advanced data visualisation was also developed, including a coordinate-based AQI heatmap, enabling smarter building management system (BMS) control. This research establishes a new benchmark for ultra-low-power, modular IAQ technology, coupled with a proven, scalable big data solution, accelerating the adoption of high-density IoT for healthier, smarter buildings. Description: Ph.D.(Melit.)

2025-01-01T00:00:00Z Dimech, Nikolai Grech, Ivan Farrugia, Russell Casha, Owen Portelli, Barnaby Micallef, Joseph https://www.um.edu.mt/library/oar/handle/123456789/143683 2026-02-16T11:07:56Z 2026-01-01T00:00:00Z

Title: Design and electronic interfacing of FR4 and polyimide PCB-based electromagnetic resonating micro-mirrors Authors: Dimech, Nikolai; Grech, Ivan; Farrugia, Russell; Casha, Owen; Portelli, Barnaby; Micallef, Joseph Abstract: This paper presents the design and fabrication of an electromagnetically actuated PCB-based resonating scanning micro-mirror for LiDAR applications, with optimization targeted towards low-cost fabrication and a high scanning angle. Traditional silicon MEMS-based micro-mirrors, while offering high precision and compatibility with CMOS processing, are limited by fragility at low scanning frequencies and costly fabrication processes. To overcome these challenges, novel alternative polymer-based substrates, namely FR4 and polyimide (PI), were employed to implement PCB-compatible mirror prototypes. Electromagnetic actuation was chosen because it achieves a high scanning angle at low driving voltages and is therefore compatible with modern electronic drive circuitry. The resonant frequency and von Mises stresses were assessed via COMSOL finite element simulations. Various scanning mirror prototypes, each featuring an optical mirror aperture of 10 mm by 10 mm, were fabricated using two different materials: 0.3 mm-thick FR4 and polyimide substrates. Different electromagnetic coil structures, embedded on the mirror plate, were evaluated with the aim of optimizing the scanning performance. The magnetic field was generated using neodymium permanent magnets. The performance attained by each prototype is compared and discussed. The scanning mirrors were designed to have a low resonant frequency in the range of 250 Hz to 550 Hz. The maximum optical scanning angle achieved for the FR4 and polyimide substrates are 31.3° and 52.1°, respectively. The paper also delves into the design of a microcontroller-based electromagnetic actuation and sensing circuitry of the mirror. Custom electronic circuitry comprising a low-power STM32L432KC microcontroller, H-bridge motor drivers for mirror actuation, and INA241-based coil voltage and current sensing was designed for this purpose. The coil voltage and current sensing circuitry enable the eventual real-time sensor less angular position feedback of the micro-mirror.

2026-01-01T00:00:00Z Casha, Owen https://www.um.edu.mt/library/oar/handle/123456789/143682 2026-02-16T11:03:15Z 2025-07-01T00:00:00Z

Title: Characterization of PCB fabrication processes for a systematic and efficient design of microstrip circuits Authors: Casha, Owen Abstract: This paper proposes an algorithm to aid in the characterization of a printed circuit board fabrication process before the design of microstrip circuits. By accurately characterizing the electrical properties of a printed circuit board process, one can achieve a systematic and efficient design of microstrip circuits with reduced iteration cycles. The algorithm employs a mean-squared-error optimization technique while making use of de-embedded scattering parameter data from some sample microstrip transmission lines, to estimate printed circuit board electrical parameters such as the tangent loss and the relative permittivity, for a particular frequency range.

2025-07-01T00:00:00Z Bengashier, Munira Casha, Owen Grech, Ivan Farrugia, Russell Micallef, Joseph Gatt, Edward https://www.um.edu.mt/library/oar/handle/123456789/142199 2025-12-15T12:53:46Z 2024-10-01T00:00:00Z

Title: Experimental investigation of thermal tuning for laterally excited bulk acoustic wave MEMS resonators using SOI bulk heating Authors: Bengashier, Munira; Casha, Owen; Grech, Ivan; Farrugia, Russell; Micallef, Joseph; Gatt, Edward Abstract: This paper presents the experimental investigation of electrothermal fine frequency tuning for a 60 MHz laterally excited contour mode bulk acoustic wave MEMS resonator, fabricated using the PiezoMUMPs multiprocess wafer process. Tuning is achieved via electrothermal SOI bulk heating of the resonator, so that its resonant frequency is shifted by inducing additional stresses in the device, as well as varying its elastic properties via a temperature change. Experimental results show that the resonant frequency decreases with an increase in the electrical heating power, which is applied to the resonator SOI bulk via two heating electrodes. For a 50-mW heating power swing, the resonator frequency varies from 61.368 MHz to 61.418 MHz. Measured results show that the SOI bulk resistance remains approximately constant over this tuning range, with a value of around 31 Ω . The discussion of the experimental results is aided and confirmed via finite element modelling and simulation.

2024-10-01T00:00:00Z