Active noise control (ANC) is a real-time process in which a system measures an external, unwanted sound source and produces a canceling waveform. The cancellation is due to destructive interference by a perfect copy of the received signal phase-shifted by 180 degrees. Existing active noise control systems process the incoming and outgoing audio on a sample-by-sample basis, requiring a high-speed digital signal processor (DSP) and analog-to-digital converters (ADCs) with strict timing requirements on the order of tens of microseconds. These timing requirements determine the maximum sample rate and bit size as well as the maximum attenuation that the system can achieve. In traditional noise cancellation systems, the general assumption is that all unwanted sound is indeterminate. However, there are many instances in which an unwanted sound source is predictable, such as in the case of a song. This thesis presents a method for active acoustic cancellation of a known audio signal using the frequency characteristics of the known audio signal compared to that of a sampled, filtered excerpt of the same known audio signal. In this procedure, we must first correctly locate the sample index for which a measured audio excerpt begins via the cross-correlation function. Next, we obtain the frequency characteristics of both the known source (WAVE file of the song) and the measured unwanted audio by taking the Fast Fourier Transform (FFT) of each signal, and calculate the effective environmental transfer function (degradation function) by taking the ratio of the two complex frequency-domain results. Finally, we attempt to recreate the environmental audio from the known data and produce an inverted, synchronized, and amplitude-matched signal to cancel the audio via destructive interference. Throughout the process, we employ many signal conditioning methods such as FIR filtering, median filtering, windowing, and deconvolution. We illustrate this frequency-domain method in Native Instruments’ LabVIEW running on the Windows operating system, and discuss its reliability, areas for improvement, and potential future applications in mobile technologies. We show that under ideal conditions (unwanted sound is a known white noise source, and microphone, loudspeaker, and environmental filter frequency responses are all perfectly flat), we can achieve a theoretical maximum attenuation of approximately 300 dB. If we replace the white noise source with an actual song and the environmental filter with a low-order linear filter, then we can achieve maximum attenuation in the range of 50-70 dB. However, in a real-world environment, with additional noise and imperfect microphones, speakers, synchronization, and amplitude-matching, we can expect to see attenuation values in the range of 10-20 dB.

Kvantalgoritmer är algoritmer implementerade på kvantdatorer där man utnyttjar kvantmekaniska särdrag för att trumfa vad som är möjligt klassiskt. Två av de mest kända algoritmerna är Grovers samt Shors algoritmer. Grovers algoritms huvudsakliga applikation är att snabbt söka efter ett eller flera element i en lista medan Shors algoritm är mycket effektiv när det kommer till faktorisering av heltal. Denna rapport studerar båda dessa algoritmer, förklarar bakomliggande teori, implementerar klassiska simuleringar av algoritmerna medelst FFT (fast Fourier transform) och diskuterar resultat med hänsyn till flera parametrar. Vi visar också att de är framgångrika i att lösa problem, och att verkligheten följer teorin på ett betryggande sätt.

Future communication systems require low latency Fast Fourier transform (FFT)computation with a small cost of area. In this study, a memory-based FFT processorwith low latency is designed. To reduce latency and maintain constant outputsample rate, a scheduling method suitable for input sample rate and clock rateis used in the radix-2 butterfly processing elements. The scheduling scheme employsa combination of ASAP and ALAP scheduling strategies. A mathematicalexpression that models FFT’s latency is given. The size of FFT, the input samplerate, and the number of processing elements are the input parameters of the expression.The effect of using pipelined processing element is also studied. Lastly,the proposed low latency design is compared with other low-latency FFT designs.The result shows that, in the 4G LTE application scenario, our memory-based designcan do the FFT computations faster with a small area.

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The Fast Fourier Transform (FFT) converts time or spatial information into the frequency domain. The FFT is one of the most widely used digital signal processing (DSP) algorithms. DSPs are used in a number of applications from communication and controls to speech and image processing. DSPs have also found their way into toys, music synthesizers and in most digital instruments. Many applications have relied on Digital Signal Processors and Application Specific Integrated Circuits (ASIC) for most of the signal processing needs. DSPs provide an adequate means of performance and efficiency for many applications as well as robust tools to ease the development process. However, the requirements of important emerging DSP applications have begun to exceed the capabilities of DSPs. With this in mind, system developers have begun to consider alternatives such as ASICs and Field Programmable Gate Arrays (FPGA). Although ASICs can provide excellent performance and efficiency, the time, cost and risk associated with the design of ASICs is leading developers towards FPGAs. A number of significant advances in FPGA technology have improved the suitability of FPGAs for DSP applications. These advances include increased device capacity and speed, DSP-oriented architectural enhancements, better DSP-oriented tools, and increasing availability of DSP-oriented IP libraries. The thesis research focuses on the design of a single precision floating-point radix-4 FFT FPGA using VHDL for real time DSP applications. The paper will go into further detail pertaining to the FFT algorithm used, the description of the design steps taken as well as the results from both simulation and synthesis. / Electrical and Computer Engineering

As Orthogonal Frequency Division Multiplexing (OFDM) becomes more prevalent in new leading-edge data rate systems processing spectral bandwidths beyond 1 GHz, the required operating speed of the baseband signal processing, specifically the Analog- to-Digital Converter (ADC) and Fast Fourier Transform (FFT) processor, presents significant circuit design challenges and consumes considerable power. Additionally, since Ultra-WideBand (UWB) systems operate in an increasingly crowded wireless environment at low power levels, the ability to tolerate large blocking signals is critical. The goals of this work are to reduce the disproportionately high power consumption found in UWB OFDM receivers while increasing the receiver linearity to better handle blockers. To achieve these goals, an alternate receiver architecture utilizing a new FFT processor is proposed. The new architecture reduces the volume of information passed through the ADC by moving the FFT processor from the digital signal processing (DSP) domain to the discrete time signal processing domain. Doing so offers a reduction in the required ADC bit resolution and increases the overall dynamic range of the UWB OFDM receiver. To explore design trade-offs for the new discrete time (DT) FFT processor, system simulations based on behavioral models of the key functions required for the processor are presented. A new behavioral model of the linear transconductor is introduced to better capture non-idealities and mismatches. The non-idealities of the linear transconductor, the largest contributor of distortion in the processor, are individually varied to determine their sensitivity upon the overall dynamic range of the DT FFT processor. Using these behavioral models, the proposed architecture is validated and guidelines for the circuit design of individual signal processing functions are presented. These results indicate that the DT FFT does not require a high degree of linearity from the linear transconductors or other signal processing functions used in its design. Based on the results of the system simulations, a prototype 8-point DT FFT processor is designed in 130 nm CMOS. The circuit design and layout of each of the circuit functions; serial-to-parallel converter, FFT signal flow graph, and clock generation circuitry is presented. Subsequently, measured results from the first proof-of-concept IC are presented. The measured results show that the architecture performs the FFT required for OFDM demodulation with increased linearity, dynamic range and blocker handling capability while simultaneously reducing overall receiver power consumption. The results demonstrate a dynamic range of 49 dB versus 36 dB for the equivalent all-digital signal processing approach. This improvement in dynamic range increases receiver performance by allowing detection of weak sub-channels attenuated by multipath. The measurements also demonstrate that the processor rejects large narrow-band blockers, while maintaining greater than 40 dB of dynamic range. The processor enables a 10x reduction in power consumption compared to the equivalent all digital processor, as it consumes only 25 mWatts and reduces the required ADC bit depth by four bits, enabling application in hand-held devices. Following the success of the first proof-of-concept IC, a second prototype is designed to incorporate additional functionality and further demonstrate the concept. The second proof-of-concept contains an improved version of the serial-to-parallel converter and clock generation circuitry with the additional function of an equalizer and parallel- to-serial converter. Based on the success of system level behavioral simulations, and improved power consumption and dynamic range measurements from the proof-of-concept IC, this work represents a contribution in the architectural development and circuit design of UWB OFDM receivers. Furthermore, because this work demonstrates the feasibility of discrete time signal processing techniques at 1 GSps, it serves as a foundation that can be used for reducing power consumption and improving performance in a variety of future RF/mixed-signal systems. / Ph. D.

Yes / A major drawback in deploying beamforming scheme in orthogonal frequency division multiplexing (OFDM) is to obtain the optimal weights that are associated with information beams. Two beam weighting methods, namely co-phasing and singular vector decomposition (SVD), are considered to maximize the signal beams for such beamforming scheme. Initially the system performance with and without interleaving is investigated using coded fast Fourier transform (FFT)-OFDM and wavelet-based OFDM. The two beamforming schemes are applied to the wavelet-based OFDM as confirmed to perform better than the FFT-OFDM. It is found that the beam-weight by SVD improves the performance of the system by about 2dB at the expense of the co-phasing method. The capacity performances of the weighting methods are also compared and discussed.

Denna studie fokuserar på att undersöka socialarbetares perspektiv angående orsakerna till ungdomars riskfyllda droganvändning samt deras strategier för att arbeta med dessa ungdomar. Genom att tillämpa en kvalitativ forskningsansats och använda ett målstyrt urval av socialarbetare inom socialtjänsten och öppenvården som deltagare, syftar studien till att få en djupare förståelse för de komplexa faktorer som ligger bakom ungas droganvändning. Metoden för dataanalys bestod av tematisk analys, där flera centrala teman identifierades. Dessa inkluderade neuropsykiatriska funktionsnedsättningar och psykisk ohälsa, ungdomars sociala sammanhang, familjens ekonomiska situation, föräldrars droganvändning, föräldrars roll i ungdomars drogavvänjning samt nya samhällsfenomen. Genom att fokusera på dessa teman kunde studien belysa olika aspekter av ungdomars droganvändning och dess komplexitet. Ett av de framträdande resultaten från studien var socialarbetarnas uppfattning om sambandet mellan bristande föräldraroll och ungdomars droganvändning. Detta indikerar att familjens dynamik och föräldrarnas engagemang spelar en avgörande roll för att förebygga och hantera riskfylld droganvändning bland ungdomar. Dessutom framkom ytterligare aspekter som påverkar ungdomars relation till droger, såsom sociala interaktioner med jämnåriga, skolans roll och nya samhällsfenomen.