Browsing by Author "Rouse, Chris"

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    A Programmatic Method For Selecting Transistors For High-Frequency Class-E Amplifiers
    (IEEE, 2023-08-22) O'Connor, Billie; Rouse, Chris; Peterson, Brent
    Radiative wireless power transfer at high efficiency can be achieved with Class-D or Class-E amplifiers. These amplifiers have achievable efficiencies that can be very high but heavily depend on transistor selection. The objective of this work was to partially automate the selection process to quickly generate near-optimal Class-E amplifier designs entirely within MATLAB®. The candidate transistor SPICE models were parsed and converted into a system of first-order ordinary differential equations. A non-stiff numerical solver was used to find steady- state solutions for candidate circuits. A simplex search algorithm was used to find the maximum-efficiency candidate circuit for the transistor. The results were also simulated in LTspice® to confirm accuracy. Eighty-four transistors were compared and seven were found to have high efficiency capabilities at 2.45 GHz. The best performing device achieved 60.6% power-added efficiency in MATLAB®, and the same device achieved 53.0% power-added efficiency in LTSpice®. The incongruency between this work and LTSpice® was small enough to justify its use for eliminating large numbers of candidate transistors.
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    Antenna development for MIMO and UHF RFID applications
    (University of New Brunswick, 2014) Rouse, Chris; Colpitts, Bruce; Petersen, Brent
    Multiple-input multiple-output (MIMO) wireless communication systems are capable of achieving significantly higher channel capacities than single-antenna systems. Furthermore, there has been a trend toward installing a larger number of cellular base stations and wireless access points (APs) over the same physical coverage area in order to meet increasing capacity demands. An in-room MIMO system—in which an AP and a user with a portable device (PD) occupy the same room—is considered. The associated channel is dominated by line-of-sight (LOS) components, which tend to increase the received signal-to-noise ratio (SNR) but can degrade MIMO performance. Therefore, the application of elevation-directional (θ-directional) AP antennas which emphasize wall-reflected non-line-of-sight (NLOS) components is investigated to improve in-room MIMO capacity. Simulation results based on the experimental set-up suggest an improvement in mean MIMO capacity on the order of 13 % coupled with a 4 % increase in mean relative MIMO gain if the AP antenna radiation patterns strike a balance between improving MIMO channel conditions and maintaining an appropriate SNR. The associated measurements revealed only a 5 % improvement in mean MIMO capacity and a small reduction in mean relative MIMO gain due to the increased multipath richness associated with the real environment. However, the measured results validated the predicted relationship between the main lobe directions of the AP antenna radiation patterns and the resulting in-room MIMO performance, suggesting that more significant improvements could be achieved for in-room MIMO systems experiencing less multipath richness. In the design of ultra-high frequency (UHF) radio-frequency identification (RFID) tags, the cost of the tag antenna is significant relative to that of the entire tag. As a result, cost-effective alternatives to copper as a UHF RFID tag antenna conductor have been explored in recent years. The feasibility of constructing such antennas using electrically conductive paper is investigated through simulations and experimental measurements. Results suggest that the conductivity of the paper is prohibitively low; however, reasonable performance would be achieved if the paper conductivity were increased by an order of magnitude.
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    Efficient and ultra low mass harmonic radar transponders for insect tracking applications
    (University of New Brunswick, 2023-11) Ala, Ramin; Rouse, Chris; Colpitts, Bruce
    The design, construction, and performance of a harmonic radar transponder with a total mass of approximately 530 µg is presented. The transponder is intended for insect tracking applications and consists of very fine wire and a small Schottky diode. It is designed for fundamental and harmonic frequencies of 10 GHz and 20 GHz, respectively. Compared to existing harmonic radar transponders, this transponder is easy to construct because the loop inductor can be implemented with a simple bend in the dipole conductor without degrading performance. Through careful design optimization, the conversion loss of the transponder is not impacted by the measures taken to minimize its mass. The expected harmonic power versus the transmitted power is estimated based on the link analysis between the transmitter and receiver of the radar, with the link analysis itself being performed via calculation, harmonic balance simulation, and full-wave simulation. The link analysis simulation predicted a received power of -66.4 dBm for a transmitted power of +22 dBm and a range of 2.4 m. The measured received power level at the harmonic frequency, obtained from the broadside of the transponder in an anechoic test chamber, is approximately -70 dBm, which agrees well with the link analysis. Simulated and measured transponder radiation patterns are also compared and show good agreement. A transponder with reduced mass compared to previous generations enables the tracking of smaller insects without diminishing their lifespan or undermining their natural flying abilities at various altitudes and ranges. The interplay between power at the fundamental and harmonic frequencies within the transponder depends on the properties of the connected diode. By conducting simulations, the relationship between these powers can be determined and formulated, enabling the optimization of the transponder’s performance. Given the fragile structure of a low mass transponder, it is crucial to assess the impact of transponder deformation on detection performance. The extent of deformation impacts the transponder’s performance, manifesting in both positive and negative effects. However, it is worth noting that the deformed transponder exhibits altered polarization, which has the potential to enhance its performance.