Asymmetrical Spacer Layer Tunnel Diode (ASPAT) for Zero Power, Microwave and Millimetre Wave Band Detection Applications

Abstract

Intelligent medical devices require miniaturization for non-invasive monitoring and diagnostics, where eliminating the need for active power sources would be beneficial. Such devices could be powered by radio frequency (RF) energy through energy harvesting or wireless power transfer. These features would also be highly attractive for applications within the Internet of Things, where each day, millions of batteries must be replaced. The work in this thesis investigates this through the design, fabrication, and testing of high-frequency integrated circuits using a novel tunnelling device, the Asymmetrical Spacer Layer Tunnel Diode (ASPAT). These consist of fully integrated Antenna-ASPAT-Matching circuits suitable for zero bias operation with frequencies ranging from 400 MHz to 26 GHz. The high level of integration in these devices reduces the chip size, permitting a low cost per device. The ASPAT is modelled using physical modelling techniques in Silvaco Atlas to evaluate the current and proposed structures to determine the potential of these devices as high-frequency detectors. Once fabricated, an equivalent circuit model was derived to design various rectifier topologies. Allowing for these designs to be complemented with an antenna with a direct conjugate match, eliminating the need for a matching network. Similar modelling techniques were applied to Gunn diodes, a diode that can generate microwave oscillations for use in radar. The models were then used to simulate and establish the viability of novel planar structures, which can simplify the fabrication and packaging processes of the device. This work was done in collaboration with Alaris Linwave Ltd, who verified these simulations with measurements. These measurements confirmed oscillation at 35.3 GHz with a power output of 0.42 mW, with further work required to mitigate the high levels of heat generation within the device. Several rectenna designs are presented throughout this thesis, ranging from 434 MHz to 26 GHz. Two of these were fabricated and tested to confirm the potential for the ASPAT diode to be used in a fully integrated rectenna. The first instance was seen in a 4x1.2 mm² design targeting 2.4 GHz, which achieved an output voltage of 0.97 V when a 2.35 GHz signal at 20 dBm was transmitted to the rectenna. A second smaller 2x0.8 mm² design targeting mm-wave frequencies saw measured results at 6.8 GHz with an output of 0.97 V. Additionally, at 23.5 GHz, this design also produced a 53.6 mV output, showing potential for K-band detection. This demonstrates that the ASPAT diode can be fully integrated into a rectenna for operation at a range of frequencies.

Date of Award	6 Jan 2025
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Mohamed Missous (Supervisor) & Krikor Ozanyan (Supervisor)