This dissertation presents a comprehensive study on the advancement of astrophysical radio, microwave, and terahertz instrumentation/simulations with three pivotal components.First, theoretical simulations of high metallicity galaxies are conducted using the supercomputing resources of Purdue University and NASA. These simulations model the evolution of a gaseous cloud akin to a nascent galaxy, incorporating variables such as kinetic energy, mass, radiation fields, magnetic fields, and turbulence. The objective is to scrutinize the spatial distribution of various isotopic elements in galaxies with unusually high metallicities and measure the effects of magnetic fields on their structural distribution. Next, I proceed with an investigation of the technology used for reading out Microwave Kinetic Inductance Detectors (MKIDs) and their dynamic range limitations tied to the current method of FPGA-based readout firmware. In response, I introduce an innovative algorithm that employs PID controllers and phase-locked loops for tracking the natural frequencies of resonator pixels, thereby eliminating the need for costly mid-observation frequency recalibrations which currently hinder the widespread use of MKID arrays. Finally, I unveil the novel Spectroscopic Lock-in Firmware (SpLiF) algorithm designed to address the pernicious low-frequency noise plaguing emergent quantum-limited detection technologies. The SpLiF algorithm harmonizes the mathematical principles of lock-in amplification with the capabilities of a Fast Fourier Transform to protect spectral information from pink noise and other low-frequency noise contributors inherent to most detection systems. The efficacy of the SpLiF algorithm is substantiated through rigorous mathematical formulation, software simulations, firmware simulations, and benchtop lab results.

Traditional imaging systems such as the human eye and optical cameras capture the scene ahead of them called the line of sight (LoS) objects. These imaging systems are limited by their lack of field of view (FoV). Information about the non-line of sight (NLoS) objects is lost due to the objects in the LoS. They are either opaque or absorb all the incident energy, allowing for no information about the NLoS scene to be transmitted back to the detector. Amongst the popular methods used for NLoS imaging, acoustic imaging [1] offers low resolutions and suffers from interference from environmental factors. Optical methods like time-of-flight (ToF) imaging perform poorly due to shorter wavelengths leading to more scattering and absorption by occluding objects in the scene. NLoS imaging with electromagnetic (EM) rays is preferred over traditional methods because of its allowance for higher spatial resolution. It is subject to lesser interference by atmospheric factors (wind, temperature gradients.)Most everyday surfaces offer diffuse and specular reflection due to their material properties. They behave as lossy mirrors enabling propagation paths between a Terahertz (THz) Imaging System and the NLoS objects. THz waves (300 GHz – 10 THz) are the least explored if not exploited band of frequencies in the EM spectrum. A THz NLoS Imaging system is a Radar (Radio Detection and Ranging) that works by recording the backscatter information received from sending out EM signals into free space where the EM signals undergo multiple bounces off different objects in the scene. Due to the inherent nature of the radars, the return information is perceived in a way that the NLoS objects are improperly depicted when reconstructed. A correction algorithm to account for this misplacement in the reconstruction of NLoS images is proposed and its implementation is discussed in detail as a part of this work. The reconstruction algorithm processes the obtained raw THz image and performs multiple stages of classification between LoS and NLoS objects using ray casting [2]. Then the information about line-of-sight objects is fed to a line detection mechanism to detect and model the detected surfaces as mirrors. Mirror folding [3] is performed starting from the farthest generations for the objects in non-line of sight. This algorithm has been evaluated with simulated images of objects behind a single wall and two walls. With the help of a scanning THz imaging system, measurements were collected in a controlled environment, and this data was fed into the implemented algorithm for testing.

Dynamic metasurface antennas (DMAs) consist of waveguides patterned with numerous metamaterial radiators loaded with switchable components (such as varactors). Byapplying different direct current (DC) signals to each element, DMAs can generate a multitude of radiation patterns ranging from directive beams useful for wireless communication to spatially diverse ones useful for computational imaging and sensing. In this thesis, DMAs are extended to conformal configurations. Using full-wave simulation, it is shown that a conformal DMA can detect the angle of the incident signal over the horizon using a two port device at a single frequency. The design and operation of the conformal DMA will be detailed. In addition, it shows that DMAs can be implemented using a single substrate layer, significantly simplifying its structure compared to conventional multiple-layer ones. Using full-wave simulation, this thesis demonstrates a mechanism to bring DC signal to metamaterial elements without requiring an extra layer. This design can be instrumental in implementing the conformal DMA in the future AoA detection was achieved over unique diode distributions of the conformal DCMA at a 10-degree resolution. Investigations into additive noise of the simulated measured data as well as the minimum amount of diode distributions to accurately detect AoA were conducted and documented within this thesis. The single-layer DMA yielded both directive and complex patterns that allow for many potential applications. With success in bringing the DC signal to the metamaterial elements on a single-layer, further advances in conformal DMAs can be achieved.

The fifth generation (5G) of cellular communication is migrating towards higher frequenciesto cater to the demand for higher data rate applications. However, in higher frequency ranges, like mmWave and terahertz, physical blockage poses a significant challenge to the large-scale deployment of this new technology. Reconfigurable Intelligent Surfaces (RISs) have shown promising potential in extending the signal coverage and overcoming signal blockages in wireless communications. However, RIS integration in networks requires high coordination between network notes, resulting in barriers to the wide adoption of RISs and similar IoT devices. To this end, this work introduces a practical study of integrating a remotely controlled RIS in an Open RAN (ORAN) compliant 5G private network with minimal software stack modifications. This thesis proposes using cloud technologies and ORAN features, such as the Radio Intelligent Controller (RIC) and eXternal Applications (xApps), to coordinate the RIS transparently with a 5G base station operation. The proposed framework has been integrated into a proof-of-concept hardware prototype with a 5.8 GHz RIS. Experimental results demonstrate that the framework can control the beam steering in the RIS accurately within the network. The proposed framework shows promising potential for near real-time RIS beamforming control with minimal power consumption overhead.

In this dissertation, enhanced coherent detection of terahertz (THz) radiation is presented for Silicon integrated circuits (ICs). In general THz receivers implemented in silicon technologies face a challenge due to the high noise figure (NF) of the low noise amplifier (LNA) and low conversion gain of the radio frequency (RF) mixers. Moreover, issues with implementing local oscillators (LOs) further compound these challenges, including power driving mixes, distribution networks, and overall power consumption, particularly for large-scale arrays. To address these inherent obstacles, two notable cases of enhancing THz receiver performance are presented. In the Sideband Separation Receiver (SSR) for space-borne applications is introduced. Implemented in SiGe BiCMOS technology this broadband SSR boasts a high Image Rejection Ratio (IRR) exceeding 20 dB across 220 – 320 GHz. Employing a modified Weaver architecture, optimized for simultaneous spectral line observation, it utilizes an I/Q double down-conversion, pushing the technological boundaries of silicon and enabling large-scale focal plane array (FPA) deployment in space. Notably, the use of a sub-harmonic down-conversion mixer (SHM) significantly reduces LO power generation challenges, enhancing scalability while maintaining minimal NF. In the 4x4 FPA active THz imager, a dual-polarized patch antenna operating at 420 GHz utilizes orthogonal polarization for RF and LO signals, coupled with a coherent homodyne power detector. Realized in 0.13µm SiGe HBT technology, the power detector is co-designing with the antenna to ensure minimal crosstalk and achieving -30dB cross-polarization isolation. Illumination of the LO enhances power detector performance without on-chip routing complexities, enabling scalability to 1K pixel THz imagers. Each pixel achieves a Noise-Equivalent Power (NEP) of 1 pW/√Hz at 420 GHz, and integration with a readout and digital filter ensures high dynamic range. Furthermore, this study explores radiation hardening techniques to mitigate single-event effects (SEEs) in high-frequency receivers operating in space. Leveraging a W-band receiver in 90 nm SiGe BiCMOS technology, matching considerations and diverse modes of operation are employed to reduce SEE susceptibility. Transient current pulse modeling, validated through TCAD simulations, demonstrates the effectiveness of proposed techniques in substantially mitigating SETs within the proposed radiation-hardened-by-design (RHBD) receiver front-end.

With the significant advancements of wireless communication systems that aim to meet exponentially increasing data rate demands, two promising concepts have appeared: (i) Cell-free massive MIMO, which entails the joint transmission and processing of the signals allowing the removal of classical cell boundaries, and (ii) integrated sensing and communication (ISAC), unifying communication and sensing in a single framework. This dissertation aims to take steps toward overcoming the key challenges in each concept and eventually merge them for efficient future communication and sensing networks.Cell-free massive MIMO is a distributed MIMO concept that eliminates classical cell boundaries and provides a robust performance. A significant challenge in realizing the cell-free massive MIMO in practice is its deployment complexity. In particular, connecting its many distributed access points with the central processing unit through wired fronthaul is an expensive and time-consuming approach. To eliminate this problem and enhance scalability, in this dissertation, a cell-free massive MIMO architecture adopting a wireless fronthaul is proposed, and the optimization of achievable rates for the end-to-end system is carried out. The evaluation has shown the strong potential of employing wireless fronthaul in cell-free massive MIMO systems. ISAC merges radar and communication systems, allowing effective sharing of resources, including bandwidth and hardware. The ISAC framework also enables sensing to aid communications, which shows a significant potential in mobile communication applications. Specifically, radar sensing data can address challenges like beamforming overhead and blockages associated with higher frequency, large antenna arrays, and narrow beams. To that end, this dissertation develops radar-aided beamforming and blockage prediction approaches using low-cost radar devices and evaluates them in real-world systems to verify their potential. At the intersection of these two paradigms, the integration of sensing into cell-free massive MIMO systems emerges as an intriguing prospect for future technologies. This integration, however, presents the challenge of considering both sensing and communication objectives within a distributed system. With the motivation of overcoming this challenge, this dissertation investigates diverse beamforming and power allocation solutions. Comprehensive evaluations have shown that the incorporation of sensing objectives into joint beamforming designs offers substantial capabilities for next-generation wireless communication and sensing systems.

Impedance is one of the fundamental properties of electrical components, materials, and waves. Therefore, impedance measurement and monitoring have a wide range of applications. The multi-port technique is a natural candidate for impedance measurement and monitoring due to its low overhead and ease of implementation for Built-in Self-Test (BIST) applications. The multi-port technique can measure complex reflection coefficients, thus impedance, by using scalar measurements provided by the power detectors. These power detectors are strategically placed on different points (ports) of a passive network to produce unique solution. Impedance measurement and monitoring is readily deployed on mobile phone radio-frequency (RF) front ends, and are combined with antenna tuners to boost the signal reception capabilities of phones. These sensors also can be used in self-healing circuits to improve their yield and performance under process, voltage, and temperature variations. Even though, this work is preliminary interested in low-overhead impedance measurement for RF circuit applications, the proposed methods can be used in a wide variety of metrology applications where impedance measurements are already used. Some examples of these applications include determining material properties, plasma generation, and moisture detection. Additionally, multi-port applications extend beyond the impedance measurement. There are applications where multi-ports are used as receivers for communication systems, RADARs, and remote sensing applications. The multi-port technique generally requires a careful design of the testing structure to produce a unique solution from power detector measurements. It also requires the use of nonlinear solvers during calibration, and depending on calibration procedure, measurement. The use of nonlinear solvers generates issues for convergence, computational complexity, and resources needed for carrying out calibrations and measurements in a timely manner. In this work, using periodic structures, a structure where a circuit block repeats itself, for multi-port measurements is proposed. The periodic structures introduce a new constraint that simplifies the multi-port theory and leads to an explicit calibration and measurement procedure. Unlike the existing calibration procedures which require at least five loads and various constraints on the load for explicit solution, the proposed method can use three loads for calibration. Multi-ports built with periodic structures will always produce a unique measurement result. This leads to increased bandwidth of operation and simplifies design procedure. The efficacy of the method demonstrated in two embodiments. In the first embodiment, a multi-port is directly embedded into a matching network to measure impedance of the load. In the second embodiment, periodic structures are used to compare two loads without requiring any calibration.

Magnetic Resonance Imaging has become an increasingly reliable source of medical imaging to obtain high quality detailed images of the human anatomy. Application specific coil or an array of coils when placed closely to the anatomy produces high quality image due to the improved spatial signal to noise ratio. Elastic RF coils have been shown to conform to the shape of the patient’s body and drastically reduce the gap between coil and anatomy. First, a major challenge faced by these elastic RF coils is the changing impedance condition as the coil takes a different shape for every individual. Next, an area that could benefit from the improved image quality and patient comfort that comes from flexible RF coil design is endorectal prostate imaging. Demonstrated in the first part of this dissertation is a modular solution to compensate the impedance mismatch. Standalone Wireless Impedance Matching (SWIM) system is an automatic impedance mismatch compensation system that can function independently of the MR scanner. The matching network consists of a capacitor array with RF switches to electronically cycle through different input impedance conditions. The SWIM system can automatically calibrate an RF coil in 3s with a reflection coefficient of less than -15dB resulting in improved Signal-to-noise ratio (SNR) of the sample image by 12% - 24%, based on sample size, when compared to a loaded coil without retuning. For the second part, we propose a novel elastic and inflatable RF coil integrated with the SWIM system for endorectal prostate imaging at 9.4T. A silicone polymer substrate filled with liquid metal alloy is designed and fabricated with a cavity to create ii inflation. This inflatable RF coil is combined with the SWIM system to automatically tune and match after inflating the RF coil for individual levels of inflation. The imaging results have shown a ~10%, ~19%, and ~25 % increase in SNR due to inflation of RF coil at different ROIs in the acquired image. Overall, the methods proposed and discussed in this thesis are a step towards a new generation of RF coil systems for both existing applications and upcoming ones.

In 1946 Felix Bloch first demonstrated the phenomenon of nuclear magnetic resonance using continuous-wave signal generation and acquisition. Shortly after in 1966, Richard R. Ernst demonstrated the breakthrough that nuclear magnetic resonance needed to develop into magnetic resonance imaging: the application of Fourier transforms for sensitive pulsed imaging. Upon this discovery, the world of research began to develop high power radio amplifiers and fast radio switches for pulsed experimentation. Consequently, continuous-wave imaging placed on the backburner.Although high power pulses are dominant in clinical imaging, there are unique advantages to low power, continuous-wave pulse sequences that transmit and receive signals simultaneously. Primarily, tissues or materials with short T2 time constants can be imaged and the peak radio power required is drastically reduced. The fundamental problem with this lies in its nature; the transmitter leaks a strong leakage signal into the receiver, thus saturating the receiver and the intended nuclear magnetic resonance signal is lost noise. Demonstrated in this dissertation is a multichannel standalone simultaneous transmit and receive (STAR) system with remote user-control that enables continuous- wave full-duplex imaging. STAR calibrates cancellation signals through vector modulators that match the leakage signal of each receiver in amplitude but opposite in phase, therefore destructively interfering the leakage signals. STAR does not require specific imaging coils or console inputs for calibration. It was designed to be general- purpose, therefore integrating into any imaging system. To begin, the user uses an Android tablet to tune STAR to match the Larmor frequency in the bore. Then, the user tells STAR to begin calibration. After self-calibrating, the user may fine-tune the calibration state of the system before enabling a low-power mode for system electronics and imaging may commence. STAR was demonstrated to isolate two receiver coils upwards of 70 dB from the transmit coil and is readily upgradable to enable the use of four receive coils. Some primary concerns of STAR are the removal of transceivers for multichannel operation, digital circuit noise, external noise, calibration speed, upgradability, and the isolation introduced; all of which are addressed in the proceeding thesis.

The work covered in this dissertation addresses two areas revolving around superconducting nanowire detector development. The first is regarding array architectureused for a large-scale system. The second involves operating under conditions that allow for a linear response in a superconducting nanowire detector. This dissertation provides the relevant theory, design, and measurements to characterize these detectors. The array architecture studied here utilizes a superconducting nanowire single photon detector embedded in an LC resonant structure, allowing multiple pixels to couple to a single transmission line and identify each one by a tuned characteristic frequency. The pixels in the array are DC-biased, allowing them to respond to absorbed single photons and avoiding any dead time associated with RF biasing. Measured results from a 16-pixel array based on chip components are analyzed. The development here directs this architecture towards integrating a proven 16-pixel design onto a single substrate with the capacity to scale to a higher pixel count and integrate into a broad range of applications. This text outlines the theory behind the proposed linear operation regime and details the considerations needed to achieve a response. The basic principle relies on the time-dependent change in kinetic inductance due to an absorbed photon. Under the conditions discussed in the text, this would allow for fast photon number resolution. However, without reaching those conditions, the detector may still operate under a higher incident photon flux. Two device designs are formulated and simulated, weighing the benefits and drawbacks of each approach. One of the device designs uses an impedance-matching taper to minimize reflections between the nanowire and 50 Ohm amplifier. The other design utilizes N parallel nanowires spanning the length of a gap along a 50 Ohm transmission line path. The tapered device is realized to a proof-of-principle stage and measured under conditions that set a limit on the device’s linear response to optical power. The performance of this detector points to areas of improvement that are addressed or circumvented in the parallel bridge design. Potential for future development is discussed for the frequency multiplexed superconducting nanowire single photon detector array and the linear mode detector.