Allann Al-Armaghany

A Dual-Band Dual-Polarization Slot Patch Antenna for GPS and Wi-Fi Applications

In this letter, a dual-band and dual-polarization capacitive-fed slot patch antenna is investigated. The proposed antenna can operate at 1.575 GHz for Global Positioning System and 2.4 GHz for Wi-Fi system with the corresponding polarizations. A 90 ° hybrid coupler chip was used to excite the right-hand circular polarization required for optimum GPS performance. For the high frequency band, a pair of linearly polarized arc-shaped slots radiating at 2.4 GHz are embedded in the circular patch. The operating bandwidths of the antenna are enhanced by the multilayered geometry, and the capacitive disks feedpoints placed between the substrate layers. The measured impedance bandwidths at the lower and high bands are 320 and 230 MHz, respectively. The measured 3-dB axial-ratio bandwidth is 120 MHz.

Feasibility study for future implantable neural-silicon interface devices

The emerging neural-silicon interface devices bridge nerve systems with artificial systems and play a key role in neuro-prostheses and neuro-rehabilitation applications. Integrating neural signal collection, processing and transmission on a single device will make clinical applications more practical and feasible. This paper focuses on the wireless antenna part and real-time neural signal analysis part of implantable brain-machine interface (BMI) devices. We propose to use millimeter-wave for wireless connections between different areas of a brain. Various antenna, including microstrip patch, monopole antenna and substrate integrated waveguide antenna are considered for the intra-cortical proximity communication. A Hebbian eigenfilter based method is proposed for multi-channel neuronal spike sorting. Folding and parallel design techniques are employed to explore various structures and make a trade-off between area and power consumption. Field programmable logic arrays (FPGAs) are used to evaluate various structures.

A GPS/Wi-Fi dual-band arc-shaped slot patch antenna for UAV application

In this paper, a dual-band capacitive-fed circular patch antenna with an arc-shaped slot is proposed for 1.575 GHz GPS and Wi-Fi 2.4 GHz applications. The antenna will be embedded on an unmanned aerial vehicle (UAV) for Wi-Fi 2.4 GHz communication with a base station and GPS reception. A circular feeding disk is sandwiched between two substrate layers. Foam is used for the bottom layer and the top layer is Rogers Duroid 5880 microwave laminate. The capacitive feeding disk is used for improving the impedance bandwidth of the antenna, so the antenna can cover 2390 to 2515 MHz for full support of the 2.4 GHz band Wi-Fi communication between UAV and GBS. The foam-Duroid stacked geometry can further enhance the bandwidths for both GPS 1.575 GHz and Wi-Fi 2.4 GHz when compared to purely Duroid form. The antenna has been simulated and fabricated. The simulation and measurement results are presented in this paper.

Development of a hybrid microwave-optical tissue oxygenation probe to measure thermal response in the deep tissue.

The design of a new non-invasive hybrid microwave-optical tissue oxygenation probe is presented, which consists of a microwave biocompatible antenna and an optical probe. The microwave antenna is capable of inducing localised heat in the deep tissue, causing tissue blood flow and therefore tissue oxygenation to change. These changes or thermal responses are measured by the optical probe using near-infrared spectroscopy. Thermal responses provide important information on thermoregulation in human tissue. The first prototype of the biocompatible antenna was developed and placed on the human calf for in vivo experiments. The measured results include oxy-, deoxy- and total haemoglobin concentration changes (ΔHbO2/ΔHHb/ΔHbT), tissue oxygenation index and the normalised tissue haemoglobin index for two human subjects. Both ΔHbO2 and ΔHbT show an increase during 5 min of microwave exposure. The thermal response, defined as the ratio of the increase in ΔHbT to the time duration, is 7.7 μM/s for subject 1 (fat thickness = 6.8 mm) and 18.9 μM/s for subject 2 (fat thickness = 5.0 mm), which may be influenced by the fat thicknesses. In both subjects, ΔHbO2 and ΔHbT continued to increase for approximately another 70 s after the microwave antenna was switched off.

Development of a Hybrid Microwave-Optical Thermoregulation Monitor for the Muscle

This paper presents the latest development of the hybrid microwave-optical thermoregulation monitor for the muscle. It is capable of warming the muscle and measuring the subsequent blood volume changes, using a novel microwave applicator with integrated optical probes. The challenge is to measure the thermoregulation response in deep tissue while minimizing any effect from the skin layer. We have introduced a skin cooling device, an additional integrated optical Laser Doppler flow monitoring probe and a temperature sensor to measure skin blood flow and temperature, respectively. The result shows that skin cooling is essential to minimize skin flow changes during microwave warming. The hybrid probe was placed on a human thigh to measure oxy/deoxy/total haemoglobin concentration changes (ΔHbO₂/ΔHHb/ΔHbT), skin flux and temperature upon microwave warming. Without skin cooling, the skin temperature was elevated by 4 °C and both ΔHbO₂/ΔHbT and skin flux increased, showing microwave warming occurring in both the skin and muscle. With skin cooling, the skin temperature was kept relatively constant. While ΔHbO₂/ΔHbT increased, the skin flux was relatively stable, showing a preferential microwave warming in the muscle, rather than the skin.

Low-Profile Orthogonally Tripolarized Antennas

A low-profile orthogonally linearly tripolarized antenna consisting of two thick-slot antennas and one half-mode substrate integrated waveguide (HMSIW) antenna has been investigated. The two thick-slot antennas radiate x- and y-directional linearly polarized waves, while the HMSIW antenna contributes to the z-directional polarized wave. The low-profile geometry is achieved by utilizing the HMSIW antenna. Isolations between the three antennas measured are lower than -20 dB, which means that the proposed antenna geometry provides good diversity gain and the channel capacity can be increased by as much as three times.

A dual band dual polarization slot patch antenna

A dual band and dual polarization slot patch antenna for Global Positioning System (GPS) and wireless LAN network with the corresponding polarizations is proposed. An L-shaped slot and a small stub are utilized to excite the desirable right-hand circular polarization (RHCP) for GPS. Meanwhile the linearly polarized electromagnetic wave for Wi-Fi communications at 2.4 GHz is contributed by an arc-shaped slot embedded circular patch. The multi-layered geometry and the capacitive feeding disk placed between the substrate layers enhance the operating bandwidths of the antenna. The achievable percentage bandwidths at the low and high bands are 6.4% and 7% respectively. The measured 3dB axial ratio (AR) bandwidth is 34 MHz, which covers the GPS L1 band.

Development of a hybrid microwave-optical deep muscle warming monitor

Elevating the temperature in tissue leads to vasodilation and therefore an increase in blood flow to reduce the excessive heat in the region, a physiological mechanism known as thermoregulation. These thermal responses have been used in various clinical applications to monitor the conditions of the spinal cord injury, vascular responses and free flap reconstruction. Currently blood flow measurements such as laser doppler flowmetry (LDF) are restricted to the skin, a rather superficial layer. To allow the investigation into deeper tissue such as the muscle, a new hybrid microwave-optical system has been developed. The deep warming is provided by a novel microwave applicator, which has a microstrip patch design operating at 2.45 GHz with a superstrate interface layer to improve the coupling of electromagnetic (EM) waves into the skin. Its design is based on computer simulations of specific absorption rate (SAR) and thermal distribution of the EM waves in a biological medium. The simulation results show that the applicator is capable of elevating the muscle temperature by 3-4 °C. The thermal response is measured by an integrated optical probe which measures tissue oxygenation changes in deep tissue using the near infrared spectroscopy technique. The hybrid microwave-optical system has been built and tested on human calves in vivo. In the talk, we will present the development of this new type of non-invasive microwave applicator for deep tissue warming.

Superficial heat reduction technique for a hybrid microwave-optical device

Microwave applicator in the form of a circularly polarized microstrip patch antenna is proposed to provide localized deep heating in biological tissue, which causes blood vessels to dilate leading to changes in tissue oxygenation. These changes are monitored by an integrated optical system for studying thermoregulation in different parts of the human body. Using computer simulations, this paper compares circularly and linearly polarized antennas in terms of the efficiency of depositing electromagnetic (EM) energy and the heating patterns. The biological model composes of the skin, fat and muscle layers with appropriate dielectric and thermal properties. The results show that for the same specific absorption rate (SAR) in the muscle, the circularly polarized antenna results in a lower SAR in the skin-fat interface than the linearly polarized antenna. The thermal distribution is also presented based on the biological heat equation. The proposed circularly polarized antenna shows heat reduction in the superficial layers in comparison to the linearly polarized antenna.