This work continues the development of phased array radar for UAS detection and tracking. The earlier 1D scanning, 4 channel BYU SAA radar is improved upon and replicated to form a network of radars. These are shown to work together for higher level tracking across multiple fields of view. Additionally, a new phased array instrument is designed and constructed with 16 channels, 2D scanning, and improved signal processing algorithms. Preliminary metrics and field results show the operation of this sensor. A new technique for measuring array mutual impedances from embedded element patterns is developed here. This technique uses an antenna range instead of a network analyzer. New mathematical relationships are built to handle cases for practical measurements and field transformations. Demonstration of this method with a 2x2 uniform rectangular array is shown and compares favorably with the mutual impedances traditionally measured with a network analyzer. A new way to measure radiation efficiency using the antenna Y factor method is demonstrated. This method does not require an expensive field measurement chamber and can be done with a simple ground shield and absorber foam. Various X band antennas have their radiation efficiency characterized and compare favorable with known efficiencies.

Modern radio astronomy’s demand for high sensitivity and wide fields of view is met through innovations that reduce receiver system noise temperatures and integrate technology supporting parallel processing and larger instantaneous bandwidths. The advanced L-band phased array camera for astronomy (ALPACA) is a fully cryogenic 69 dual-polarized dipole PAF and digital beamformer back end for the Green Bank Telescope. This instrument will form 40 dual-polarized beams yielding a 0.35 sq. deg field of view on the sky with a 305.2 MHz processing bandwidth. The target system noise temperature is 27 K. A structured technique to map critically sampled and oversampled polyphase filter banks (PFBs) onto a systolic array for implementation on a field programmable gate array (FPGA) is shown. This method provides unique insights into the operation of these algorithms. A case study for an oversampled PFB operating at 666.67 Msps shows that these designs effectively utilize FPGA resources, maintain high-throughput, and are flexible solutions for varied application requirements. A new class of FPGA, the Radio Frequency System-on-Chip (RFSoC), is integrated as a full-functioning software-defined hardware platform in an open-source signal processing toolchain. This provides astronomers with essential hardware for contemporary scientific research. The demonstration for an experimental technique for measuring antenna radiation efficiency using the antenna Y factor method is presented. The noise contribution of the ALPACA dipole when operating at cryogenic temperatures is estimated. Our findings show that the antenna is expected to contribute less than 1 K to the instrument’s overall system noise temperature. Research contributions of this work are: the integration of new high-performance digital hardware in radio astronomical PAF digital back ends, an open-source RFSoC signal processing development toolchain, an oversampled PFB using an FPAG-based systolic array design, and estimating the cryogenic noise temperature of an ALPACA dipole from its radiation efficiency.

Phased array feeds (PAFs) are a promising new technology for astronomical radio telescopes. While PAFs have been used in other fields, the demanding sensitivity and calibration requirements in astronomy present unique new challenges. This dissertation presents some of the first astronomical PAF results demonstrating the lowest noise temperature and highest sensitivity at the time (66 Kelvin and 3.3 m^2/K, respectively), obtained using a narrowband (425 kHz bandwidth) prototype array of 19 linear co-polarized L-band dipoles mounted at the focus of the Green Bank 20 Meter Telescope at the National Radio Astronomy Observatory (NRAO) in Green Bank, West Virginia. Results include spectral line detection of hydroxyl (OH) sources W49N and W3OH, and some of the first radio camera images made using a PAF, including an image of the Cygnus X region. A novel array Y-factor technique for measuring the isotropic noise response of the array is shown along with experimental measurements for this PAF. Statistically optimal beamformers (Maximum SNR and MVDR) are used throughout the work. Radio-frequency interference (RFI) mitigation is demonstrated experimentally using spatial cancelation with the PAF. Improved RFI mitigation is achieved in the challenging cases of low interference-to-noise ratio (INR) and moving interference by combining subspace projection (SP) beamforming with a polynomial model to track a rank 1 subspace. Limiting factors in SP are investigated including sample estimation error, subspace smearing, noise bias, and spectral scooping; each of these factors is overcome with the polynomial model and prewhitening. Numerical optimization leads to the polynomial subspace projection (PSP) method, and least-squares fitting to the series of dominant eigenvectors over a series of short term integrations (STIs) leads to the eigenvector polynomial subspace projection (EPSP) method. Expressions for the gradient, Hessian, and Jacobian are given for use in numerical optimization. Results are given for simulated and experimental data, demonstrating deeper beampattern nulls by 6 to 30dB. To increase the system bandwidth toward the hundreds of MHz bandwidth required by astronomers for a fully science-ready instrument, an FPGA digital backend is introduced using a 64-input analog-to-digital converter running at 50 Msamp/sec and the ROACH processing board developed at the University of California, Berkeley. International efforts to develop digital back ends for large antenna arrays are considered, and a road map is proposed for development of a hardware correlator/beamformer at BYU using three ROACH boards communicating over 10 gigabit Ethernet.