Development of FFTS for Radio Astronomy

Sheng Li, Zhen-Hui Lin, Ji Yang

Wen-Ying Duan, Qi-Jun Yao, Sheng-Cai Shi

Purple Mountain Observatory, Chinese Academy of Sciences

Nov. 28th, 2011 Sun-Moon Lake, Taiwan2011 Advanced Telescope and Instrument Technology Conference

Nov. 28th, 2011 2011 Advanced Telescope and Instrument Technology Conference 2

Requirement: Broadband & high resolution

Why broad bandwidth?

Δf/fo= Δv/c For submillimeter-wave observation

Nov. 28th, 2011 2011 Advanced Telescope and Instrument Technology Conference 3

Requirement: Broadband & high resolution

Why broad bandwidth?

Δf/fo= Δv/c For high-redshift objects survey

100MHz bandwidth only covers ~300km/s!!!

Credit: Young, J. S et al. 1984, ApJ, 287, 153

Nov. 28th, 2011 2011 Advanced Telescope and Instrument Technology Conference 4

Requirement: Broadband & high resolution

Why high frequency resolution? For observe fine structure of molecular lines

For knowing the kinematics characteristics of objects

Credit: Schnee, S. et al. 2005, ApJ, 624, 254

N2H+(J=1-0) :93.171621GHz93.171917GHz93.172053GHz93.173480GHz93.173777GHz93.173967GHz93.176265GHz

Nov. 28th, 2011 2011 Advanced Telescope and Instrument Technology Conference 5

Evolvement: From analog to digital

Analog back-end system

Filter Bank Spectrometer

Acousto-Optical Spectrometer

Filterbank & AOS4x1GHz@1MHz

HerschelHerschel

HiFi

Nov. 28th, 2011 2011 Advanced Telescope and Instrument Technology Conference 6

Evolvement: From analog to digital

Digital back-end system

Auto/Cross-Correlation Spectrometer ALMAALMA

Correlator, 3bits or 2bits8x2GHz@15.625MHz8x250MHz@244kHz

SMASMA

Correlator, 2bits8x24x82MHz@ 812.5 kHz

Nov. 28th, 2011 2011 Advanced Telescope and Instrument Technology Conference 7

FFTS: Principle

Autocorrelator/FFT Spectrometer

Nov. 28th, 2011 2011 Advanced Telescope and Instrument Technology Conference 8

Spectral system evolvement at PMO

AOS x 313.7m telescope at Delingha

Single FFTSFFTS x 2 x 9

2006,082010,11

Nov. 28th, 2011 2011 Advanced Telescope and Instrument Technology Conference 9

FFTS: Firmware development

Firmware Structure based on AC240

Hardware structure of AC240AC240 Board

Nov. 28th, 2011 2011 Advanced Telescope and Instrument Technology Conference 10

FFTS: Firmware development

Parallel pipeline FFT core structure

Nov. 28th, 2011 2011 Advanced Telescope and Instrument Technology Conference 11

FFTS: Firmware development

Program language: VHDLDesign tool: ISE 9.1

Resource utility

Nov. 28th, 2011 2011 Advanced Telescope and Instrument Technology Conference 12

FFTS: Software development

设备初始化

图形界面创建

子线程创建

频谱及状态显示

标准源观测

谱线 OTF 观测

谱线 5 点观测

命令组接收

命令解析

数据发送

命令接收

数据发送

Human-computer interaction - Quicklook GUI

Data processing – Multithreading

（ 9 data processing sub-thread, 2 communication sub-thread ）

Data Communication (TCP/IP, 1Gb/s) 、 Data Storage (NFS)

Nov. 28th, 2011 2011 Advanced Telescope and Instrument Technology Conference 13

FFTS: Software development

Quicklook GUISingle FFTS

9-Pixel FFTS

BECU case 1BECU case 2

Nov. 28th, 2011 2011 Advanced Telescope and Instrument Technology Conference 14

FFTS: Performance

Test results

Integration Time: 32.768msDynamic Range: >30dB

ADC Full Scale: 1VStability/Allan-Variance: ~3000s

Nov. 28th, 2011 2011 Advanced Telescope and Instrument Technology Conference 15

FFTS: Performance

Observation results

SiO(2-1)

Nov. 28th, 2011 2011 Advanced Telescope and Instrument Technology Conference 16

FFTS: Back-end system integration

Integration with data storage system

Gigabits internet

20~40 MB/s data transfer rate with OTF1Gb/s internet connectionRAID-5 disk array for both high speed and reliability34T bytes storage capacity (data of a month)

Nov. 28th, 2011 2011 Advanced Telescope and Instrument Technology Conference 17

Future plan

Back-end for dome A telescope Broadband with high resolution Low power consumption High level of integration High stability

2011-2012, hardware, firmware & software development• 2~2.5 GHz bandwidth, 16 k channels(122 kHz)

2013-2015• >=4 GHz bandwidth, >=32k channels

Dome A Telescope

Nov. 28th, 2011 2011 Advanced Telescope and Instrument Technology Conference 18

Thanks for your attention~