Terahertz technology has received continuously increasing attention in recent years. A key enabler of this technology is the photo-conductive antenna. A time-domain Norton equivalent circuit representing the antenna and a time-step algorithm provide the tools for analysis and design of such structures. However, the antenna impedance impulse response must be known beforehand. In this thesis, a more comprehensive characterization of the algorithm is provided through a detailed investigation. A numerical error in its output is discovered, the source of which identified, and an error minimization solution proposed. Using the newly acquired knowledge of the algorithm’s properties, an infinite photo-conductive slot is analyzed. First, a time-domain energy balance equation is derived using switched capacitor formalism, and verified. Then, a comparison to constant antenna impedance approximation is performed. A study on the frequency and time-domain far-fields, as well as, on the influence of parameters is also performed. Finally, the analysis is extended to a 1D connected array, in which the mutual coupling and performance are investigated.

Conventional techniques for audio monitoring, including Passive Audio Monitoring (PAM), often call for the use of environmentally unsustainable and challenging equipment. This among other limitations can disrupt the very environment that is meant to be studied and may also limit the ability to observe an ecosystem in its natural state.

This thesis explores the possibility of a passive wireless biodegradable microphone for the purpose of audio monitoring in fragile environments. This project introduces the "The BioThing - A biodegradable microphone for monitoring biodiversity".
The BioThing uses a biodegradable material, to address the current challenges of state-of-art monitoring techniques. The design utilises a resonant cavity to function as a listening device through the implementation of the backscatter wave modulation technique and with a primary working resonant frequency of around 1.7 GHz.

This report presents a detailed analysis of the device's design and function to optimize its geometry for various frequencies, operational ranges, and functionalities by investigating the effect of critical parameters such as the variable capacitances namely the distance between the diaphragm and the tuning post, and the distance between the tuning post and the antenna. Additionally, it also analyses the effect of device geometry on resonance properties by investigating the impact of parameters such as tuning post height, membrane thickness, and cavity height. The report also investigates the possibilities for device enlargement for long-distance operation and device miniaturisation to facilitate faster degradation. This optimization process aims to achieve improved performance, ultimately leading to a more effective listening device. A prototype was fabricated using commercially available Zinc and plant-based resin.

This research works towards a new generation of ecologically sustainable audio monitoring equipment that will allow a deeper insight into the soundscapes of fragile environments without disturbing the ecosystems.

In this thesis, a direction-reconfigurable wide-input-range radio frequency energy harvesting
system is described. In order to improve the receiving power and the performance in low
power range, three blocks of optimization are placed in different part of the system. Subse
quently, a two paths 3-stage body biased cross-coupled differential-drive rectifier with antenna
beam forming control and 3-bit capacitor bank is designed and fabricated in a standard 180nm
CMOS technology. The rectifier is brought at resonance with four high-Q patch antennas by
means of a control loop that compensates for any variation at the antenna-rectifier interface
and a beam forming control that change the largest receiving direction of the antennas to allow
higher power input in multiple directions. A body-bias method with cross-coupled capacitors
and a diode to limit the body-bias voltage makes the rectifier works better in low power range.
The chip is integrated with four patch antennas. Measurements in an anechoic chamber at
2.45 GHz demonstrate a–10dBm sensitivity for 1 V output across a capacitive load. The
end-to-end power conversion efficiency reaches 65% at–6dBm.

New generations of mobile communications are much more demanding in order to provide critical real-time services and extremely fast connections that have become feasible with 5G. A wider spectrum is needed to achieve such high data rates and millimeter-wave frequencies are used for this purpose. Adaptive beamforming is applied at base stations through active phased antenna arrays to shape and steer the beams at each user, so coverage distance is extended and resource sharing among users is more efficient.

Different approaches to the design of active phased arrays for mm-wave base stations to realize the "one beam per user" concept are analyzed and compared. Particular attention to mutual interference between the beams is given. A novel aperiodic, uniformly-fed, active integrated antenna array design is presented as an appealing alternative to minimize user inference based on a multi-disciplinary array synthesis approach. Implementation challenges of such aperiodic array are investigated and the performance is compared to those of a periodic array. The complete design and its simulation results show an interference reduction around 6 dB and similar gain as compared to the regular array taken as reference.