Abstract
The detailed knowledge of the Milky Way radio emission is important to characterize galactic foregrounds masking extragalactic and cosmological signals. The update of the global sky models describing radio emissions over a very large spectral band requires high sensitivity experiments capable of observing large sky areas with long integration times. Here, we present the design of a new 10 GHz (X-band) polarimeter digital back-end to map the polarization components of the galactic synchrotron radiation field of the Northern Hemisphere sky. The design follows the digital processing trends in radio astronomy and implements a large bandwidth (1 GHz) digital complex cross-correlator to extract the Stokes parameters of the incoming synchrotron radiation field. The hardware constraints cover the implemented VLSI hardware description language code and the preliminary results. The implementation is based on the simultaneous digitized acquisition of the Cartesian components of the two linear receiver polarization channels. The design strategy involves a double data rate acquisition of the ADC interleaved parallel bus, and field programmable gate array device programming at the register transfer mode. The digital core of the back-end is capable of processing 32 Gbps and is built around an Altera field programmable gate array clocked at 250 MHz, 1 GSps analog to digital converters and a clock generator. The control of the field programmable gate array internal signal delays and a convenient use of its phase locked loops provide the timing requirements to achieve the target bandwidths and sensitivity. This solution is convenient for radio astronomy experiments requiring large bandwidth, high functionality, high volume availability and low cost. Of particular interest, this correlator was developed for the Galactic Emission Mapping project and is suitable for large sky area polarization continuum surveys. The solutions may also be adapted to be used at signal processing subsystem levels for large projects like the square kilometer array testbeds.
Highlights
The plethora of radio and microwave experiments exploring large radio spectral bands from the Megahertz to many dozens of Gigahertz promise a very high science impact on galactic and extragalactic radio astronomy (RA)
Bergano et al SpringerPlus (2016) 5:487 with many instruments, including those to be performed as parts of Key Science projects of the square kilometer array (SKA) and its pathfinders and precursors require the refining of the radio global sky models (GSM) and knowledge improvement of galactic foreground radiation
The mapping of the polarized emission between 5 and 10 GHz projects is the target of several projects such as the Galactic Emission Mapping project (GEM) (Torres et al 1996) and the more recent C-Band All Sky Survey (CBASS) project (King et al 2010) to improve the polarized foreground subtraction obtained from cosmic microwave background (CMB) missions
Summary
The plethora of radio and microwave experiments exploring large radio spectral bands from the Megahertz to many dozens of Gigahertz promise a very high science impact on galactic and extragalactic radio astronomy (RA). Bergano et al SpringerPlus (2016) 5:487 with many instruments, including those to be performed as parts of Key Science projects of the square kilometer array (SKA) and its pathfinders and precursors require the refining of the radio global sky models (GSM) and knowledge improvement of galactic foreground radiation This improvement enables a better separation of the different emission critical components to the analysis of the cosmic microwave background (CMB) observations obtained by ground and space missions above 70 GHz (Komatsu et al 2011; Planck Collaboration 2013). We apply it to the development of a new 10 GHz polarimeter, with 1 GHz bandwidth, we achieve five times more bandwidth for large sky area polarimetry surveys This solution uses standards ADCs and an Altera Cyclone III FPGA providing a very cost-effective performance
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