Abstract Details
| Name: Kaushal Buch Affiliation: GMRT, NCRA-TIFR Conference ID: ASI2018_1648 Title : Initial Developments in the Design and Implementation of FPA Beamformer for the Expanded GMRT Authors and Co-Authors : Kaushal D. Buch, Atul Ghalame, Bela Dixit, Siddhesh Hande, Priya Hande, Ajithkumar B, Jayaram N. Chengalur Giant Metrewave Radio Telescope, NCRA-TIFR, Pune, India Abstract Type : Contributed Talk Abstract Category : Instrumentation and Techniques Abstract : The Expanded GMRT (eGMRT) is a proposal for carrying out a feasibility study for possible expansions to the Giant Metrewave Radio Telescope (GMRT). These expansions would help GMRT retain its status as one of the most sensitive instruments at low radio frequencies. The three possible areas proposed for expansion are to increase the field of view (in the 550-900 MHz band), increase angular resolution and improve sensitivity to the extended radio emission. In this talk, we would focus on increasing the field of view using Focal Plane Array (FPA) and the initial developments for the associated beamformer. Various hardware and software beamformer implementation options for the development of prototype FPA beamformer would be described along with the future plans. We will discuss the computational and cost estimates for a 300 MHz, 30-beam FPA beamformer for the eGMRT. Narrowband and wideband FPA beamformers are being designed using the CASPER* tool-flow and implemented on the FPGA boards (called ROACH), which serve as a backend to the 144-element FPA procured from ASTRON. Both, the narrowband (32 MHz bandwidth) and the wideband (300 MHz bandwidth) beamformers comprise of a single ROACH board receiving inputs from a 64-channel ADC boards and high-speed ADC boards, respectively. Results from a 16-input, 4-beam, 1024 spectral channel, narrowband beamformer would be described. A novel scalable design for packetized wideband beamformer and its testing using multiple ROACH boards is underway. This design carries out cross-correlation on recorded data. To make the design scalable and modular, beamforming for a smaller set of elements is implemented on individual ROACH boards and the final beamforming is carried out in the acquisition computer. In parallel, a software-based approach using CPU-GPU platform is being developed. This would enable raw voltage recording and narrowband beamforming. Various beamforming algorithms are being studied and would be implemented in the software for FPA calibration. The current status, test methodology, and future projections including the initial test results from a free-space test range will be discussed. Also, plans for commissioning the FPA on a dish to carry out experimental observations with these beamformers would be described. *https://casper.berkeley.edu/ |