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.



College and Department

Ira A. Fulton College of Engineering and Technology



Date Submitted


Document Type





phased array feed, signal processing, beamformer, polyphase filter bank



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Engineering Commons