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A new technique to de-Dopplerize microphone signals from moving sources of sound is derived. Currently available time domain de-Dopplerization techniques require oversampling and interpolation of the microphone time data. In contrast, the technique presented in this dissertation performs the de-Dopplerization entirely in the frequency domain eliminating the need for oversampling and interpolation of the microphone data. As a consequence, the new de-Dopplerization technique is computationally more efficient. The new de-Dopplerization technique is then implemented into a frequency domain beamforming algorithm to locate moving sources of sound. The mathematical formulation for the implementation of the new de-Dopplerization technique is presented for sources moving along a linear trajectory and for sources moving along a circular trajectory, i.e. rotating sources. The resulting frequency domain beamforming method to locate moving sound sources is then validated using numerical simulations for various source configurations (e.g. emission angle, emission frequency, and source velocity), and different processing parameters (e.g. time window length). Numerical datasets for sources with linear motion as well as for rotating sources were simulated. For comparison purposes, selected datasets were also processed using traditional time domain beamforming. The results from the numerical simulations show that the frequency domain beamforming method is at least 10 times faster than the traditional time domain beamforming method with the same performance. Furthermore, the results show that as the number of microphones and/or grid points increase, the processing time for the traditional time domain beamforming method increases at a rate 20 times larger than the rate of increase in processing time of the new frequency domain beamforming method. / Ph. D.

A common problem encountered in phased array signal processing is how to remove sources of interference from a desired signal. Two existing methods to accomplish this are the Linearly Constrained Minimum Variance (LCMV) beamformer and the Side-Lobe Canceller (SLC). LCMV provides better performance than SLC, but comes with much higher computational costs. The Steered Auxiliary Beam Canceller (SABC) presented in this thesis is a new algorithm developed to improve the performance of SLC without the computational costs of LCMV. SABC performs better than SLC because it uses high-gain auxiliary channels for cancellation. This new technique is now possible because digital arrays allow for direction finding algorithms such as Estimation of Signal Parameters via Rotational Invariance Techniques (ESPRIT) to estimate the directions of the interference sources. With this added knowledge, high gain beams similar to the main beam may be used as auxiliaries instead of low-gain antenna elements. Another contribution is a method introduced to calculate the computational complexity of LCMV, SLC, and SABC much more accurately than existing methods which only provide order-of-magnitude estimates. The final contribution is a derivation of the signal loss experienced by SLC and SABC and simulations that verify the performance of LCMV, SLC, and SABC. / Master of Science

This thesis investigates optical feed methods for phased array antennas. The technical and practical limitations are analyzed and an optimum design is determined. This optimum optical feed is a two-beam interferometric approach which uses acoustooptic phase control. The theory is derived; a computer model is developed; and the limitations are determined. Design modifications are suggested which reduce limitations and greatly extend the range of applications. / Master of Science

Use of Slotted Waveguide Antenna Stiffened Structures (SWASS) in future commercial and military aircraft calls for the development of an airworthiness certification procedure. The first step of this procedure is to provide a computationally low-cost method for modeling waveguide antenna arrays on the scale of an aircraft skin panel using a multi-fidelity model. Weather detection radar for the Northrop Grumman X-47 unmanned air system is considered as a case study. COMSOL Multiphysics is used for creating high-fidelity waveguide models that are imported into the MATLAB Phased Array Toolbox for large-scale array calculations using a superposition method. Verification test cases show that this method is viable for relatively accurate modeling of large SWASS arrays with low computational effort. Additionally, realistic material properties for carbon fiber reinforced plastic (CFRP) are used to create a more accurate model. Optimization is performed on a 12-slot CFRP waveguide to determine the waveguide dimensions for the maximum far-field gain and separately for the maximum critical buckling load. Using the two separate optima as utopia points, a multi-objective optimization for the peak far-field gain and critical buckling load is performed, to obtain a balance between EM performance and structural strength. This optimized waveguide is then used to create a SWASS array of approximately the same size as an aircraft wing panel using the multi-fidelity modeling method that is proposed. This model is compared to a typical conventional weather radar system, and found to be well above the minimum mission requirements. / Master of Science

Thanks to a small wavelength (large bandwidth) combined with a low loss transmission window around 94 GHz and 120 GHz, the 75-120 GHz frequency band in millimeter wave (mm-wave) provides a promising opportunity for high data rate long range wireless communications and high-resolution imaging systems. Large-scale phased arrays have been exploited in such application for their beam forming and null steering capabilities, resulting in high directivity and improved SNR. But growing DC power consumption (Pdiss) in such large scale arrays has become an on-going concern along with noise, linearity and phase resolution trade-offs in current phased array architectures. To address these issues, we propose a power efficient phase shifter (PS) architecture based on quadrature hybrid coupler, which leverages the benefits of conventional active and passive PSs at mm-wave. The phase shifter has low loss, resulting in low power dissipation and the power domain phase interpolation by the quadrature hybrid gives low phase error and high linearity. We design W-band (90-100 GHz) phased array transmit and receive (T/R) modules in 130 nm SiGe BiCMOS technology based on the proposed PS and our measurements show high power efficiency with the lowest power consumption at W-band to our knowledge (18mW and 26mW power dissipations at receiver (Rx) and transmitter (Tx) front-ends respectively). Rx shows 23 to 25 dB peak gain, 6 to 9.3 dB NF and Tx can deliver upto 7 dBm output power with 18% power efficiency. Moreover, our PS can achieve 5-bit phase resolution with <2 degrees RMS phase error and provides 0 dBm saturated output power at 94 GHz. The phase shifter (PS) is also scalable beyond W-band without significant loss. We demonstrate this with a 120 GHz two channel phased array receiver (Rx), where a single channel shows 15.6 dB peak gain with Pdiss=53 mW which shows one of the highest gain efficiency (gain/Pdiss) among D-band phased arrays. We can further reduce the power consumption by leveraging the bidirectional signal processing at the phased array front-end. To achieve this, we designed a W-band bidirectional variable gain amplifier with gain variation ranging from 6 to -1 dB at 94 GHz which can be used along with bidirectional PS. The amplifier will replace the lossy SPDT switch in the conventional bidirectional approach, reducing the overall power consumption. / Ph. D.

Over the years, phased array antennas have provided electronic scanning with high gain and low sidelobe levels for many radar and satellite applications. The need for higher bandwidth as well as greater scanning ability has led to research in the area of aperiodically spaced antenna arrays. Aperiodic arrays use variable spacing between antenna elements and generally require fewer elements than periodically spaced arrays to achieve similar far field pattern performance. This reduction in elements allows the array to be built at much lower cost than traditional phased arrays. This thesis introduces the concept of aperiodic phased arrays and their design via optimization algorithms, specifically Particle Swarm Optimization. An axial mode helix is designed as the antenna array element to obtain the required half power beamwidth and bandwidth. The final optimized aperiodic array is compared to a traditional periodic array and conclusions are made. / Master of Science