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

2. 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

3. 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 1.5 GHz: 212 kHz
Stability (spec. Allan Variance): > 1000 sec.
Calibration- and aging free digital processing
B.Klein Berkeley 2008

4. 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

5. 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: kg
Manufacturer: Vertex Antennentechnik
B.Klein Berkeley 2008

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

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

8. AFFTS :: FFTS-Master
B.Klein Berkeley 2008

9. 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 300 MHz
B.Klein Berkeley 2008

10. The Lab-FFTS
B.Klein Berkeley 2008

11. 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

12. 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 spectral channels, ENBW: 53 kHz
1 x 500 MHz bandwidth, 1 x spectral channels, ENBW: 35 kHz
1 x 100 MHz bandwidth, 1 x spectral channels, ENBW: 7 kHz (in lab test)
2 x 500 MHz bandwidth, 2 x 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

13. 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 April 2008
B.Klein Berkeley 2008

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

15. 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

16. 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 32µs :: ~64 MBytes/sec
B.Klein Berkeley 2008

17. 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

18. (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 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

19. 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, 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 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

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