This study uses vertical mirror optical waveguide reflector and bending waveguide to fabricate semiconductor ring resonators. By using multimode interference couplers with specific width and length that generate distinctive energy distribution to achieve the power splitting of 85:15. We integrate vertically deep etching turning mirror to reflect optical mode, and reduce the component size to 37.6%. In fabrication process, this study applies multiple wet etching technique to form the waveguide structure. First, we use wet etching technique to etch ridge waveguide and turning mirror, and then perform deep etching in the periphery of bending and turning region to reduce the bending loss. Finally, the etching mask is lifted off, and the wafer is polished and sliced for measurement. After measuring the signal, we can compute waveguide loss by Fabry-perot resonant situation. The waveguide loss is 59.6dB/cm. Power splitting of 90:10 is achieved. The free spectral range (FSR) is 72GHz for the ring resonators.

published_or_final_version / Linguistics / Master / Master of Arts

published_or_final_version / abstract / toc / Electrical and Electronic Engineering / Master / Master of Philosophy

This study investigated the influence of training on interference in younger and older adults using the Eriksen flanker task. Does flanker interference differ with age and, as practice progresses, does the pattern of interference change? Younger and older adults were given five sessions of training on the flanker task over five successive days. On each trial, participants saw a central target letter flanked vertically by two flanker letters; the flankers could be either compatible or incompatible with the target. Participants were to respond to the identity of the central letter, ignoring the flanker letters. Although older adults were slower overall than younger adults in responding, the two groups showed virtually identical overall benefits from practice. Critically, the two age groups showed equivalent and constant interference due to incompatible flankers at all stages of practice. In the flanker paradigm, aging slows response execution without affecting attention within a trial or learning across trials.

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With the increase of the number of radios and antennas on today’s systems, the risk of co-site interference is very high. Intermodulation product and antenna coupling are two common sources of interference. The thesis investigates some features of a radio system, like antenna types, receiver parameters, intermodulation products and isolation, and suggests how this knowledge can be used to minimize the risk of co-site interference. The goal is to maximize the isolation between the antennas, by good frequency planning, the use of filters and taking great care in antenna placement. A first version of an analysis software was developed where transmitters and receivers can be paired and evaluated. An intermodulation product calculator was also implemented, to easily find which products are an issue and where they originate. The goal of the software is to be simple to use and easy to adapt to different setups and situations. It should also be easy to upgrade with new features.

Although the effect of working memory (WM) load on the magnitude of distractor interference has been studied extensively, a common characteristic in prior research is that the target and distractors belong to different objects. The present experiments investigate the effect of WM load on distractor interference when the relevant and irrelevant information is part of the same object. In two experiments, participants saw stimulus displays that consisted of a memory set followed by a Stroop color stimulus. The tasks were to respond to the color of the stimulus first and then to a memory probe. The principal manipulations were the relationship between the color and meaning of the Stroop stimulus (neutral vs. incongruent) and the level of WM load (high vs. low). The results show that WM load had little effect on the magnitude of Stroop interference. These results were consistent with previous research which shows that WM load plays a limited role in the efficiency of selective attention when the extent of attentional focus was held constant across different WM load conditions. They also emphasize the importance of stimulus structure in understanding selective attention in general, and distractor processing in particular.

Doctor of Philosophy / The next generation mobile networks are expected to provide multimedia applications with a high quality of service. On the other hand, interference among multiple base stations (BS) that co-exist in the same location limits the capacity of wireless networks. In conventional wireless networks, the base stations do not cooperate with each other. The BSs transmit individually to their respective mobile stations (MS) and treat the transmission from other BSs as interference. An alternative to this structure is a network cooperation structure. Here, BSs cooperate with other BSs to simultaneously transmit to their respective MSs using the same frequency band at a given time slot. By doing this, we significantly increase the capacity of the networks. This thesis presents novel research results on a noncooperative transmission scheme and a cooperative transmission scheme for multi-user multiple-input-multiple-output orthogonal frequency division multiplexing (MIMO-OFDM). We first consider the performance limit of a noncooperative transmission scheme. Here, we propose a method to reduce the interference and increase the throughput of orthogonal frequency division multiplexing (OFDM) systems in co-working wireless local area networks (WLANs) by using joint adaptive multiple antennas(AMA) and adaptive modulation (AM) with acknowledgement (ACK) Eigen-steering. The calculation of AMA and AM are performed at the receiver. The AMA is used to suppress interference and to maximize the signal-to-interference-plus-noise ratio (SINR). The AM scheme is used to allocate OFDM sub-carriers, power, and modulation mode subject to the constraints of power, discrete modulation, and the bit error rate (BER). The transmit weights, the allocation of power, and the allocation of sub-carriers are obtained at the transmitter using ACK Eigen-steering. The derivations of AMA, AM, and ACK Eigen-steering are shown. The performance of joint AMA and AM for various AMA configurations is evaluated through the simulations of BER and spectral efficiency (SE) against SIR. To improve the performance of the system further, we propose a practical cooperative transmission scheme to mitigate against the interference in co-working WLANs. Here, we consider a network coordination among BSs. We employ Tomlinson Harashima precoding (THP), joint transmit-receive beamforming based on SINR (signal-to-interference-plus-noise-ratio) maximization, and an adaptive precoding order to eliminate co-working interference and achieve bit error rate (BER) fairness among different users. We also consider the design of the system when partial channel state information (CSI) (where each user only knows its own CSI) and full CSI (where each user knows CSI of all users) are available at the receiver respectively. We prove analytically and by simulation that the performance of our proposed scheme will not be degraded under partial CSI. The simulation results show that the proposed scheme considerably outperforms both the existing noncooperative and cooperative transmission schemes. A method to design a spectrally efficient cooperative downlink transmission scheme employing precoding and beamforming is also proposed. The algorithm eliminates the interference and achieves symbol error rate (SER) fairness among different users. To eliminate the interference, Tomlinson Harashima precoding (THP) is used to cancel part of the interference while the transmit-receive antenna weights cancel the remaining one. A new novel iterative method is applied to generate the transmit-receive antenna weights. To achieve SER fairness among different users and further improve the performance of MIMO systems, we develop algorithms that provide equal SINR across all users and order the users so that the minimum SINR for each user is maximized. The simulation results show that the proposed scheme considerably outperforms existing cooperative transmission schemes in terms of the SER performance and complexity and approaches an interference free performance under the same configuration. We could improve the performance of the proposed interference cancellation further. This is because the proposed interference cancellation does not consider receiver noise when calculating the transmit-receive weight antennas. In addition, the proposed scheme mentioned above is designed specifically for a single-stream multi-user transmission. Here, we employ THP precoding and an iterative method based on the uplink-downlink duality principle to generate the transmit-receive antenna weights. The algorithm provides an equal SINR across all users. A simpler method is then proposed by trading off the complexity with a slight performance degradation. The proposed methods are extended to also work when the receiver does not have complete Channel State Informations (CSIs). A new method of setting the user precoding order, which has a much lower complexity than the VBLAST type ordering scheme but with almost the same performance, is also proposed. The simulation results show that the proposed schemes considerably outperform existing cooperative transmission schemes in terms of SER performance and approach an interference free performance. In all the cooperative transmission schemes proposed above, we use THP to cancel part of the interference. In this thesis, we also consider an alternative approach that bypasses the use of THP. The task of cancelling the interference from other users now lies solely within the transmit-receive antenna weights. We consider multiuser Gaussian broadcast channels with multiple antennas at both transmitter and receivers. An iterative multiple beamforming (IMB) algorithm is proposed, which is flexible in the antenna configuration and performs well in low to moderate data rates. Its capacity and bit error rate performance are compared with the ones achieved by the traditional zero-forcing method.