Abstract Details
| Name: S Harshavardhan Reddy Affiliation: GMRT-NCRA-TIFR Conference ID: ASI2015_655 Title : Backend system development for uGMRT Authors and Co-Authors : GMRT Backend Team Abstract Type : Poster Abstract Category : Instrumentation and Techniques Abstract : GMRT is undergoing upgradation to achieve the instantaneous bandwidth of 400MHz and near seamless coverage between 50-1500 MHz. This upgradation requires development and installation of new backend systems with latest technology available. The new backend system processes the RF signals coming from the 30 antennas over optical fibre cables and outputs the visibilty data for all the GMRT baselines. The GMRT Analog Backend(GAB) conditions and down-converts the RF signals to baseband frequencies before being fed to the digital backend, the GMRT Wideband Backend(GWB). The related analog circuits use highly stable local oscillator circuits which facilitates different frequency settings for each antenna, when needed. The oscillators are locked to a master Time and Frequency standard which is based on a GPS disciplined Rubidium unit. The analog backend system also provide facilities for extensive signal monitoring, variable attenuators for signal level adjustment, switchable filter bank etc. The GMRT Wideband Backend(GWB) is a hybrid backend developed using the recent advances computing and networking technologies. ADCs followed by FPGA boards are used for sampling and packetising the data, while CPU- GPUs are used to perform the correlation and beamformation operation. The model implemented is a time-slicing model where each CPU-GPU gets a slice of contiguous time series data of all antennas on which it performs operations like FFT, Multiplication and Accumulation(MAC) and beamformation. The total compute and IO requirements for GWB are around 10 Tflops and 25.6 GB/s respectively. The new system will also have additional features like narrow band modes for spectral line observations, Walsh demodulation facility, RFI filtering schemes etc. An 8-antenna prototype has been developed and integrated with the GMRT receiver and is in operation now. The design and development details are presented along with the results of the tests done on the prototypes. The extrapolation of these designs for the 32-antenna backend for the complete GMRT system will also be discussed. |