This paper presents a low cost, compact and lightweight RF switching system for wearable head imaging applications. The proposed switching system is made from commercial off-the-shelf components (COTS). The switching system provides a wideband performance which covers operating frequency band from DC to 4 GHz. A low power microcontroller is integrated with two RF switches as a control system. An array of twelve wideband monopole antennas were connected to the proposed switching circuit and its performance was evaluated using an artificial human head phantom. To verify the performance of the system, a haemorrhagic stroke was mimicked by placing a spherical target of 30 mm in diameter inside the fabricated head phantom. Two data acquisition methods were applied using the switching system. In the first method, the reflection coefficients of the antennas were collected for healthy and unhealthy brain injury cases. For the second method, the transmission coefficients of the antennas were collected by utilising four antennas in the array as transmitting antennas while the rest of the antennas act as receiving antennas. We demonstrates that the proposed compact switching system could be used for future real-time wearable detection systems embedded in various headgear products.
Screen printing is a known method to produce disposable and low-cost sensors. Depending on the application such as food analysis, environmental health monitoring, disease detection and toxin detection, screen-printed electrodes can be fabricated in a variety of sizes and shapes. Modification of the electrode's material and geometrical dimension may be done to produce effective screen-printed three-electrodes system. Thus, the effects of varying the working electrode (WE) area in radius of 0.9 mm to 2 mm, gap spacing between electrodes ranging from 0.5 mm to 1.6 mm, and the width of the counter electrode in range of 0.7 to 1.3 mm on sensor's performance was investigated in this study through COMSOL simulation. It was found that the modification of the working electrode radius and the gap between the electrodes has the most significant effect on sensor's performance, while modifying the width of the counter electrode (CE) shows no significant effect. Sensors with 0.9 mm radius or 2.54 mm² WE area and 0.5 mm gap spacing has shown the optimum performance with 0.026 A/m² current density which is contributed by 0.044 pF capacitance value. As a conclusion, regardless of the width of counter electrodes, a smaller gap between electrodes and a smaller working area would lead to optimal performance of a screenprinted three-electrode sensor system.
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