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A high performance cost-effective digital complex correlator for an X-band polarimetry survey.

Bergano M, Rocha A, Cupido L, Barbosa D, Villela T, Boas JV, Rocha G, Smoot GF - Springerplus (2016)

Bottom Line: The hardware constraints cover the implemented VLSI hardware description language code and the preliminary results.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Electronics, Telecommunication and Informatics (DETI), Instituto de Telecomunicações, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal.

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.

No MeSH data available.


Front-end block diagram for the left channel depicting the Cartesian components AL and BL for the left circular polarization
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Fig2: Front-end block diagram for the left channel depicting the Cartesian components AL and BL for the left circular polarization

Mentions: The polarimeter sensitivity and dynamic range depend on antenna, system noise and integration time, thus influencing the digital design of the backend, where final detection of Stokes parameters takes place. The expected polarized signal power equivalent temperature at 10 GHz is ~0.1 mK so a long integration time is needed. The antenna is a 9 m Cassegrain type with an HPBW ϴ3dB = 0.28° and equipped with a corrugated feed horn. A polarizer followed by an orthomode transducer (OMT) carries the separation between left and right circular polarizations (LHCP and RHCP). Both polarization channels are further amplified until they are digitized. The analog front end block diagram of the receiver for one channel is depicted in Fig. 2. In short, the analog chain is responsible for amplifying the signals to the required digital entry levels. Since the galactic synchrotron emission is linearly polarized, we designed the polarimeter to output the linear U and V Stokes parameters through the correlation of the incoming circular polarization components and thus minimize calibration systematics and output Stokes parameters.Fig. 2


A high performance cost-effective digital complex correlator for an X-band polarimetry survey.

Bergano M, Rocha A, Cupido L, Barbosa D, Villela T, Boas JV, Rocha G, Smoot GF - Springerplus (2016)

Front-end block diagram for the left channel depicting the Cartesian components AL and BL for the left circular polarization
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4837755&req=5

Fig2: Front-end block diagram for the left channel depicting the Cartesian components AL and BL for the left circular polarization
Mentions: The polarimeter sensitivity and dynamic range depend on antenna, system noise and integration time, thus influencing the digital design of the backend, where final detection of Stokes parameters takes place. The expected polarized signal power equivalent temperature at 10 GHz is ~0.1 mK so a long integration time is needed. The antenna is a 9 m Cassegrain type with an HPBW ϴ3dB = 0.28° and equipped with a corrugated feed horn. A polarizer followed by an orthomode transducer (OMT) carries the separation between left and right circular polarizations (LHCP and RHCP). Both polarization channels are further amplified until they are digitized. The analog front end block diagram of the receiver for one channel is depicted in Fig. 2. In short, the analog chain is responsible for amplifying the signals to the required digital entry levels. Since the galactic synchrotron emission is linearly polarized, we designed the polarimeter to output the linear U and V Stokes parameters through the correlation of the incoming circular polarization components and thus minimize calibration systematics and output Stokes parameters.Fig. 2

Bottom Line: The hardware constraints cover the implemented VLSI hardware description language code and the preliminary results.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Electronics, Telecommunication and Informatics (DETI), Instituto de Telecomunicações, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal.

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.

No MeSH data available.