Many opportunities exist in medical ultrasound research for experimenting with novel designs, both of transducers and of signal processing techniques. However any experiment must have a reliable platform on which to develop these techniques. In my thesis work, I have designed, built, and tested a high-speed reconfigurable ultrasound beamforming platform. The complete receive beamformer system described in this thesis consists of hardware, firmware, and software components. All of these components work together to provide a platform for beamforming that is expandable, high-speed, and robust. The complexity of the operations being performed is hidden from the user by a simple to use and accessible software interface. Existing beamformer hardware is usually designed for real-time 2D image formation often using serial processing. The platform I built uses parallel processing in order to process ultrasound images 100 times faster than conventional systems. Conventional hardware is locked to a single or small number of similar transducers, while my design can be on-the-fly reprogrammed to work with nearly any transducer type. The system is also expandable to handle any size of device, while conventional systems can only handle a fixed number of device channels. The software I have created interfaces with the hardware and firmware components to provide an easy way to make use of the system’s reconfigurability. It also delivers a platform that can be simply expanded to host post-processing or signal analysis software to further fulfill a researcher’s needs. / Thesis (Ph.D, Physics, Engineering Physics and Astronomy) -- Queen's University, 2010-12-10 11:23:01.961

Ultra-wideband (UWB) wireless communication is a topic of intense research. It has the potential for superior performance over comparable narrowband wireless systems. UWB wireless systems transmit pulses that have energy concentrated mainly from 3.1 GHz to 10.6 GHz. These pulses are transmitted at very low energy levels so as not to interfere with many existing wireless systems that operate in the same band. UWB communication systems can benefit significantly from beamforming networks where the received signal strength depends on angle of arrival. This thesis focuses on the characterization of a digital beamformer in a real wireless channel. The beamformer is evaluated using various methods to judge its performance impact on a real UWB communication system. An analog UWB beamformer in hardware is derived by taking advantage of a simple microwave circuit realization. The analog UWB beamformer is studied and its feasibility is evaluated.

Ultra-wideband (UWB) wireless communication is a topic of intense research. It has the potential for superior performance over comparable narrowband wireless systems. UWB wireless systems transmit pulses that have energy concentrated mainly from 3.1 GHz to 10.6 GHz. These pulses are transmitted at very low energy levels so as not to interfere with many existing wireless systems that operate in the same band. UWB communication systems can benefit significantly from beamforming networks where the received signal strength depends on angle of arrival. This thesis focuses on the characterization of a digital beamformer in a real wireless channel. The beamformer is evaluated using various methods to judge its performance impact on a real UWB communication system. An analog UWB beamformer in hardware is derived by taking advantage of a simple microwave circuit realization. The analog UWB beamformer is studied and its feasibility is evaluated.

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<p dir="ltr">We propose a hardware driven solution to high dynamic range (HDR) imaging in the form of a single metasurface lens. Our design consists of a metasurface capable of forming nine low dynamic range (LDR) sub-images of varying intensities scaling by a factor of 2 onto an imaging sensor. After synthetically verifying the functionality of our design, the metasurface is fabricated and a prototype system is constructed for real world experiments. Utilizing the experimental system, the compatibility of our extracted LDR sub- images with pre-existing exposure bracketing solutions for multi-image HDR fusion is demonstrated. The resulting HDR images are highly robust to scene motion due to the instantaneous capture of multi-exposure LDR sub-images allowing for HDR video capabilities.</p>

In many engineering applications, including radar, sonar, communications and seismology, the direction of impinging signal wavefronts can be used to discriminate between competing sources. Often these source signals cover a wide bandwidth and conventional narrowband beamforming techniques are ineffective, since spatial resolution varies significantly across the band. In this thesis we consider the problem of beamforming for broadband signals, primarily when the spatial response remains constant as a function of frequency. This is called a frequency invariant beamformer (FIB).¶ Rather than applying the numerical technique of multi-parameter optimisation to solve for the beamformer parameters, we attempt to address the fundamental nature of the FIB problem. The general philosophy is to use a theoretical continuous sensor to derive relationships between a desired FI beampattern and the required signal processing structure. Beamforming using an array of discrete sensors can then be formulated as an approximation problem. This approach reveals a natural structure to the FIB which is otherwise buried in a numerical optimisation procedure.¶ Measured results from a microphone array are presented to verify that the simple FIB structure can be successfully implemented. We then consider imposing broadband pattern nulls in the FI beampattern, and show that (i) it is possible to impose an exact null which is present over all frequencies, and (ii) it is possible to calculate a priori how many constraints are required to achieve a null of a given depth in a FIB. We also show that the FIB can be applied to the problem of broadband direction of arrival (DOA) estimation and provides computational advantages over other broadband DOA estimators.¶ Through the theoretical continuous sensor approach, we show that the FIB theory can be generalised to the problem of designing a general broadband beamformer (GBB) which realizes a broadband angle-versus-frequency beampattern specification. Coupled with a technique for radial beampattern transformation, the GBB can be applied to a wide class of problems covering both nearfield beamforming (in which the shape of the impinging wavefront must be considered and farfield beamforming (which is simplified by the assumption of planar wavefronts) for a broadband beampattern specified over both angle and frequency.

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Recognition of speech at the receiver end generally gets degraded in distant talking atmospheres of laptops, teleconfereing, video conferences and in hands free telephony, where the quality of speech gets contaminated and severely disturbed because of the additive noises. To make useful and effective, the exact speech signals has to be extracted from the noise signals and the user has to be given the clean speech. In such conditions the convenience of microphone array has been preferred as a means of civilizing the quality of arrested signals. A consequential growth in laptop technology and microphone array processing have made possible to improve intelligibility of speech while communication. So this contention target on reducing the additive noises from the original speech, beside design and use of different algorithms. In this thesis a multi-channel microphone array with its speech enhancement of signals to Wiener Beamformar and Generalized side lobe canceller (GSC) are used for Laptops in a noisy environment. Systems prescribed above were implemented, processed and evaluated on a computer using Mat lab considering SNR, SNRI as the main objective of quality measures. Systems were tested with two speech signals, among which one is Main speech signal and other is considered as Noise along with another random noise, sampling them at 16 KHz .Three Different source originations were taken into consideration with different input SNR’s of 0dB, 5dB, 10dB, 15dB, 20dB, 25dB. Simulation Results showed that Noise is been attenuated to a great extent. But Variations in SNR and SNRI has been observed, because of the different point origination of signals in the respective feilds.Variation in SNR and SNRI is been observed when the distance between the main speech originating point and microphone is too long compared to the noise signals. This states that origination of signals plays a huge role in maintaining the speech quality at the receiver end. / D.No 4-22, Gandla street, papanaidupeta-517526 chittoor district,Andhra pradesh India naveenkumarthupalli@gmail.com

Phased array receivers are a set of antenna elements that are capable of forming multiple simultaneous beams over a field of view. In radio astronomy, the study of deep space radio sources, a phased array feed (PAF) is placed at the focus of a large dish telescope that spatially samples the focal plane. PAFs provide an increase in the field of view as compared to the traditional single pixel horn feed, thereby increasing survey speed while maintaining low sensitivity. Phased arrays are also capable of radio frequency interference (RFI) mitigation which is useful in both radio astronomy and wireless communications when detecting signals in the presence of interferers such as satellites. Digital signal processing algorithms are used to process and analyze data provided by phased array receivers. During the commissioning of the Focal-plane L-band Array feed for the Green Bank telescope (FLAG), sensitivity consistent with an equivalent system temperature below 18 K was measured. To demonstrate the astronomical capability of the receiver, a pulsar (PSR B2011+38) was detected, and an HI source (NGC4258) was mapped with the real-time beamformer and fine channel correlator, respectively. This work also details improvements made to the software of the FLAG digital backend such as the design and implementation of an algorithm to remove scalloping ripple from the spectrum of two cascading polyphase filter banks (PFB). This work will also provide a brief introduction to a model-based beam interpolation algorithm capable of increasing spatial resolution of radio source maps as well as reducing time spent performing calibration. The development of a phased array receiver digital back end for the Office of Naval Research (ONR) is also detailed. This broadband system will be capable of communication in hostile RFI-rich environments with the aid of a real-time RFI mitigation algorithm currently implemented in software. This algorithm will be compatible with other PAF receiver systems and will enable RFI mitigation in other applications such as radio astronomy. This work will provide details on the implementation of this algorithm, the development and modification of other system software as well as full system tests of the 150 MHz bandwidth receiver have been conducted and will be shown in this document.