Fast Fourier Transform Spectrometer (FFTS) Broadband Fast Fourier Transform Spectrometer (FFTS) Bernd Klein Max-Planck-Institut für Radioastronomie, Bonn - Germany - B.Klein Berkeley 2008

FFTS :: A short “history” ... 2.5 GHz >8k channels 0.1 year instantaneous bandwidth [GHz] 2004 2005 2006 2007 2008 2009 2003 2.0 1.5 1.0 0.5 2.5 1.5 GHz 8k channels 1 GHz 8k channels 1.8 GHz 8k channels 2 x 50 MHz 1k channels 100 MHz ? channels B.Klein Berkeley 2008

Instantaneous bandwidth: 0.1 – 1.8 GHz FFTS :: The MPIfR-Board ADC FPGA Signal pro- cessing ADC Synthesizer (AD9517-n) Power Supply (1.2, 1.9, 2.5, 3.3 V) 100 MBit/s Ethernet Analog Power Supply GPS/IRIG-B Time decoder 5 Volt IF input (0 - 3 GHz) Data Instantaneous bandwidth: 0.1 – 1.8 GHz Spectral resolution @ 1.5 GHz: 212 kHz Stability (spec. Allan Variance): > 1000 sec. Calibration- and aging free digital processing B.Klein Berkeley 2008

FFTS :: Stability ADC Transistor as „Heater“ The spectroscopic variance between two 1 MHz broad channels, separated by 800 MHz within the band, was determined to be stable on a timescale of ~4000 s. B.Klein Berkeley 2008

APEX :: Atacama Pathfinder EXperiment Telescope: Location: Llano de Chajnantor, 50 km east San Pedro de Atacama, northern Chile Coordinates: Latitude : 23º00"20.8' South Longitude :67º45'33.0" West Elevation : 5105 m Diameter: 12 m f/D: 8 Beam width: (FWHM) 7.8" * (800 / f [GHz]) Main reflector: 264 aluminum panels, average panel surface rms 5 micron Surface accuracy: 17 micron rms Pointing accuracy: 2" rms over sky Mounting: Alt-Az Receiver cabins: 2 Nasmyth + 1 Cassegrain Mass: 125 000 kg Manufacturer: Vertex Antennentechnik B.Klein Berkeley 2008

CHAMP+ :: Array-RX 660/850 GHz window B.Klein Berkeley 2008

AFFTS :: Array-FFTS for APEX Bandwidth: 32 x 1.5 GHz = 48 GHz (option 58 GHz) Spec. channels: 32 x 8k = 256k channels @ 212 kHz B.Klein Berkeley 2008

AFFTS :: FFTS-Master B.Klein Berkeley 2008

AFFTS :: Software / Monitoring FFTS Control Software: multi-threaded software / Linux one thread per FFTS-board (smoothing, leveling, RFI-filter, ..) communication telescope / FFTS: SCPI protocol (UDP/ASCII), e.g. APEX:AFFTS:band1:cmdBandwidth 1500 data flow: TCP (header + spectra) FFTS Monitor Tool (LabView) test line @ 300 MHz B.Klein Berkeley 2008

The Lab-FFTS B.Klein Berkeley 2008

FFTS :: Signal Processing Unlike the conventional windowed-FFT processing, a more efficient polyphase pre-processing algorithm has been de- veloped with significantly reduced frequency scallop, less noise bandwidth expansion, and faster sidelobe fall-off. Frequency response of the optimized FFT signal processing pipeline Equivalent noise bandwidth = 1.16 x frequency spacing B.Klein Berkeley 2008

FFTS :: FPGA configurations Today, implemented FFTS board / FPGA configurations are: 1 x 1.5 GHz bandwidth, 1 x 8192 spectral channels, ENBW: 212 kHz (default core) 1 x 1.8 GHz bandwidth, 1 x 8192 spectral channels, ENBW: 255 kHz 1.9 GHz is possible by using selected FPGAs with highest speed grades! 1 x 750 MHz bandwidth, 1 x 16382 spectral channels, ENBW: 53 kHz 1 x 500 MHz bandwidth, 1 x 16384 spectral channels, ENBW: 35 kHz 1 x 100 MHz bandwidth, 1 x 16384 spectral channels, ENBW: 7 kHz (in lab test) 2 x 500 MHz bandwidth, 2 x 8192 spectral channels, ENBW: 71 kHz (in lab test) The Equivalent Noise Bandwidth (ENBW) is the width of a fictitious rectangular filter such that the power in that rectangular band is equal to the (integrated) response of the actual filter. B.Klein Berkeley 2008

FFTS :: in world-wide use The superior performance, high sensitivity and reliability of MPIfR FFT spectrometers has now been demonstrated at many telescopes world-wide. Spectrum towards Orion-KL. The high-excitation CO(7-6) transition at 806 GHz was observed with the central pixel of the CHAMP+ array. W3(OH) SgrA circum-nuclear disk CO(2–1) Further details: B. Klein, et al., Proceedings of the 19th ISSTT, Groningen 28-30 April 2008 http:://www.mpifr-bonn.mpg.de/staff/bklein B.Klein Berkeley 2008

The Effelsberg FFTS (EFFTS) Spectroscopy :: 16 x 100 - 500 MHz bandwidth, 8192 and 16384 channels Pulsar Search :: 16 x 250 MHz bandwidth, 512 channels, 32/64µs dumping Applications: Installation & Commissioning: August this year! B.Klein Berkeley 2008

The Effelsberg FFTS :: hardware Dual input ADC :: National ADC08D1500, 2 x 750 MHz bandwidth GigaBit Ethernet :: Marvell 88E1111, UDP: 85 MBytes/sec cont. Board modifications: I-Input Q-Input TCP 100 Mbits/s Marvell GigaBit chip UDP 1 Gbits/s B.Klein Berkeley 2008

EFFTS :: pulsar signal processing Performance: FPGA processing :: 250 MHz bandwidth & 8-tab polyphase filterbank with 512 channels, ENBW: 515 kHz Dump time [µs] :: 32, 64 or 128, 16 x 512 channels (32-bit float) 1k Bytes tail (dump counter, GPS/IRIG-B time,...) Data rate @ 32µs :: ~64 MBytes/sec B.Klein Berkeley 2008

FFTS :: The 2.5 GHz development Currently in development: The 2.5 GHz bandwidth FFTS for GREAT siehe kommentar eingefügt. Goal: 2.5 GHz instantaneous bandwidth with adequate spectral resolution (~100 kHz), to be operational in time for SOFIA‘s early science flights in summer 2009! B.Klein Berkeley 2008

(on-off)/off + test line @ 2.4 GHz 2.5 GHz Bandpass FFTS :: The 2.5 GHz development First (lab) results: 2.5 GHz with 512 channels (on-off)/off + test line @ 2.4 GHz 2.5 GHz Bandpass siehe kommentar eingefügt. Next step: Increase the number of spectral channels by replacing the Virtex-4 SX55 by the new Virtex-5 SX240T or 3/4 x Virtex-4 SX55. B.Klein Berkeley 2008

MPIfR FFTS :: Summary Advantages of our new generation of compact FFT spectrometers: FFTS provide high instantaneous bandwidth (1.5/1.8 GHz demonstrated in field tests, 2.5 GHz achieved in lab tests) with many thousands frequency channels, thus offering wideband observations with high spectral resolution without the complexity of the IF processing in a hybrid configuration. They provide very high stability by exclusive digital signal processing. Allan stability times of > 1000 seconds have been demonstrated routinely. Field-operations of our FFTS over the last 3 years have proven to be very reliable, with calibration- and aging-free digital processing boards, which are swiftly re-configurable by Ethernet for special observation modes. Low space and power requirements – thus safe to use at high altitude (e.g. APEX at 5100-m) as well as (potentially) on spacecrafts and satellites. Production cost are low compared to traditional spectrometers through use of only commercial components. B.Klein Berkeley 2008

FFTS :: Contact, Distribution Contact: For further information about the MPIfR FFT spectrometer technology, future developments and applications, please contact Bernd Klein (bklein@mpifr.de) at the Max-Planck-Institut für Radioastronomie in Bonn, Germany. http://www.fft-spectrometer.info Distribution of standard FFT spectrometer (1.5 GHz / 8192 channels) by: http://www.radiometer-physics.de B.Klein Berkeley 2008