Abstract

Modern radio astronomy instruments require a wide field of view and high sensitivity. To this effect, BYU and Cornell University have developed the Advanced L-band Phased Array Camera for Astronomy (ALPACA), a fully cryogenic 69 dual-pol dipole array that produces 80 beams on the sky with 305 MHz instantaneous bandwidth centered on 1500 MHz. Integration testing has demonstrated proper beamforming and calibration, and ALPACA has been commissioned as an all-sky monitor to search for bright transients. Commissioning testing for ALPACA measured an element system noise temperature of 24 K and a beamformed system noise temperature of 17 K, making ALPACA one of the lowest phased array system noise temperatures in the world. Beamforming tests on the sun have also demonstrated that multiple beams can be calibrated and steered to different positions on the sky. ALPACA can operate in multiple scientific observation modes, which requires an oversampled first stage channelizer. A study of whether oversampling increases pulsar parameter estimation error showed that the increase is very minimal for ALPACA's oversampling ratio. Increasing radio frequency intereference (RFI) on Earth has led to new radio telescope concepts for use on the moon. The proposed Lunar Farside Technosignatures and Transients Telescope (LFT3) also requires a wide field of view but in a low-power environment. The LFT3 array consists of 48 dual-pole Vivaldi elements which need to be beamformed to produce 10 beams on the sky. Given the limitation on compute power, LFT3 utilizes a passive analog beamformer, which are traditionally bandwidth-limited. A modified Blass matrix was developed and tested as a novel wideband analog beamformer. On-the-bench and over-the-air measurements demonstrated that this modified Blass matrix beamformer can produce multiple beams across a 300--900 MHz bandwidth.

Degree

PhD

College and Department

Ira A. Fulton College of Engineering; Electrical and Computer Engineering

Rights

https://lib.byu.edu/about/copyright/