Kurtosis Spectrometer

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The Spectral Kurtosis (SK) Spectrometer was built by Zhiwei Liu for Korean Solar Radio Burst Locator (KSRBL). This instrument utilizes four of these 500 MHz bandwidth SK spectrometers in parallel, to achieve a 2 GHz instantaneous bandwidth that is time multiplexed over the entire DC-18 GHz radio frequency range.

The unique aspect of the spectrometer is that it accumulates both power and power-squared statistics which are then used to develop a "spectral kurtosis"(SK) estimator as described by Nita et al. (2007, PASP 119, 805). The SK estimator is used offline for real-time detection and excision of RFI embedded in the received signal. The required power and power-squared data are broadcast by the FPGA via fast ethernet and converted to the SK estimator using software implemented in LabVIEW.

Contents

Specifications

Frequency channels: 2048 (4096 real samples per spectrum)
Clock input: 1000 MHz
Signal input: 500 - 1000 MHz
Integration time: 25 ms
Polyphase filter: 4taps, Hamming window
Output: 100 Mbit Ethernet, 32-bit per spectrum bin
Libraries used: mlib_devel 7.1
hardware: iBOB, iADC

Source Files

Bin.jpg Kurtosis Spectrometer Model File and PowerPC Source, Rev: May 2009 Info_circle.png


Bin.jpg Kurtosis Spectrometer .bit File, Rev: May 2009 Info_circle.png


Bin.jpg Kurtosis Spectrometer LabVIEW data receiver, Rev: Aug 2009 Info_circle.png


Bin.jpg Kurtosis Spectrometer based on ROACH board, Rev: Nov 2009 Info_circle.png


Documentation

Initialization Commands:

regwrite reg_shift -1

This sets the shifting schedule through the FFT. -1 means every sample is divided by 2 at every stage.

regwrite reg_coeff 4096

There is a scaling factor at the output of wide_band_FFT block. The fix point position is 12, so 4096=2^13 actually is 1.

regwrite reg_acclen 6249

This sets the integration time to 6250 spectra (around 25.6 ms at 1000 MHz ADC clock)

regwrite reg_sync_period 25600000

This sets the sync period to 25600000 FPGA clocks

regwrite reg_arm 0
regwrite reg_arm 1

The rising edge of reg_arm starts the operation and reset the accumulated spectra counter to 0. You can also use external signal to trigger the arm (connect the external signal to SMA1 of iBOB).

startudp 169 254 128 5 6969

This sends the udp packets to 169.254.128.5 with destination port 6969.


Packets Format:

Each UDP packet is 1045 bytes (21 bytes of header, 1024 bytes of raw data).

Header Format:

Byte    Type    Descr., Example
0-3     uint32  spectrum number
4       uint8   register value of reg_power_bitselect
5       uint8   register value of reg_power2_bitselect
6       uint8   register value of reg_power_bfacc_bitselect
7       uint8   Reserved
8-11    uint32  Number of Accumulation -1, eg.3999->4000 accumulation
12      uint8   number of packets per spectrum(power and power^2)
13-20   ------  Reserved

Results

Watch video of Spectral Kurtosis elimination of Radio Frequency Interference (RFI)

Resource Utilization

Logic Utilization:
  Number of Slice Flip Flops:      32,313 out of  47,232   68%
  Number of 4 input LUTs:          15,378 out of  47,232   32%
Logic Distribution:
  Number of occupied Slices:       19,761 out of  23,616   83%
Total Number 4 input LUTs:         23,450 out of  47,232   49%
  Number used as logic:            15,378
  Number used as a route-thru:        562
  Number used for Dual Port RAMs:     556
    (Two LUTs used per Dual Port RAM)
  Number used as 16x1 RAMs:             4
  Number used as Shift registers:   6,950
 
  Number of bonded IOBs:              152 out of     692   21%
    IOB Flip Flops:                   175
    IOB Master Pads:                   19
    IOB Slave Pads:                    19
    IOB Dual-Data Rate Flops:           1
  Number of PPC405s:                   2 out of       2  100%
  Number of JTAGPPCs:                  1 out of       1  100%
  Number of Block RAMs:               146 out of     232   62%
  Number of MULT18X18s:                64 out of     232   27%
  Number of GCLKs:                      3 out of      16   18%
  Number of DCMs:                       3 out of       8   37%
  Number of GTs:                        0 out of      16    0%
  Number of GT10s:                      0 out of       0    0%
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