https:///weradocs/WERA_FullCal_lsq.shtml Last update:

WERA HF Radar Software - Process Full Calibration Measurements

wera_fullcal_lsq

wera_fullcal_lsq processes a series of calibration measurements to compensate for variations in amplitude and phase as a function of range cell. 'wera_fullcal_lsq' uses the known frequency offset provided with the header to identify the signal to be analysed. No search for a peak frequency is done.

The 'standard' calibration file performs this corrections for one fixed range, which is range cell 20.

Full calibration adds a range-dependent correction for the phase and provides an individually measured 'gain ramp' for each receiver channel, ie. the new 'gain ramp' in the /home/wera/etc/<sitename>.fullcal file is used instead of the fixed WERA Gain File in /home/wera/etc/params.cfg.

wera_fullcal_lsq delivers two calibration files:

  1. /home/wera/etc/calibration.wera (as a replacement for the 'standard' calibration)
  2. /home/wera/etc/<sitename>.fullcal (new values for range-dependent corrections)
Existing measurements which only used /home/wera/etc/calibration.wera can be improved by connecting the Calibration Box with short cables to the receiver inputs (even after the measurement campaign in the lab if no receiver modules have been exchanged/replaced). In this case, only the /home/wera/etc/<sitename>.fullcal file should be used; do not overwrite the existing /home/wera/etc/calibration.wera file. The Full Calibration data should live in /home/wera/etc.

First investigations have shown that the use of the Full Calibration data is not that important to get correct results,
but it can slightly increase the performance of the Beam Forming and Direction Finding algorithms. Larger influence is expected at high range cell numbers (>128).

The use of Full Calibration data has been implemented within the following programs:

The name of the Full Calibration file is site dependent and passed to the software through the site section in Params_cfg (parameter FCAL_nnn).
If the file defined by FCAL_nnn is present, the programs will use this information instead of the standard 'gain ramp'.

Full Calibration measurements can be started from WeraDesk by selecting the Acquisition Mode 'Full Calibration'.

wera_fullcal_lsq reads all information needed on number of channels, length of timeseries, etc. from the header (first 512 bytes of data file).
The following box shows a typical output generated by wera_fullcal_lsq: 

wera@ifmwera1:~/Fortran> wera_fullcal_lsq ~/data/koolina/fullcal/20031500011_koo.cal ~/data/koolina/fullcal/20031500512_koo.cal
 WERA_FullCal_lsq V1.0.2 Linux:
 Processing file:  /home/wera/data/koolina/fullcal/20031500011_koo.cal
 t_sweep  =    0.26000 s
 mt       =        768 samples
 nfft     =        256 samples
 nant     =         16 antennas
 i_offset =    5965233 DDS steps
 f_offset =   -3.84616 Hz
 Antenna:   DC values [V]:        RMS values: [V]       Cal values:
  1         0.00915    0.01236    0.41063    0.41034    1.03015    1.03088
  2         0.01349    0.01219    0.42214    0.41824    1.00206    1.01138
  3         0.01357    0.00794    0.38626    0.38449    1.09513    1.10018
  4         0.01262    0.01244    0.40062    0.40635    1.05588    1.04098
  5         0.00894    0.00488    0.42073    0.42301    1.00540    1.00000
  6         0.00783    0.01328    0.38804    0.39279    1.09011    1.07693
  7         0.01732    0.01388    0.37738    0.37853    1.12090    1.11750
  8         0.01182    0.01286    0.41836    0.41453    1.01111    1.02046
  9         0.01136    0.00369    0.38196    0.38215    1.10746    1.10692
 10         0.02466    0.01580    0.40650    0.40506    1.04062    1.04430
 11         0.02195    0.01780    0.40942    0.40387    1.03318    1.04738
 12         0.01403    0.01130    0.39578    0.39705    1.06878    1.06538
 13         0.01329    0.01448    0.41026    0.40624    1.03108    1.04128
 14         0.02401    0.02446    0.36836    0.37135    1.14836    1.13912
 15         0.00686    0.01197    0.40835    0.40627    1.03589    1.04120
 16         0.00628    0.00653    0.41209    0.41221    1.02649    1.02619
 Antenna: Freq.:    Phase: Peak-1    Peak     Peak+1       LSQ   I/Q-Balance
  1        -3.84615        0.000     0.000     0.000       0.00   89.55
  2        -3.84615      -10.498   -10.500   -10.501     -10.50   88.57
  3        -3.84615        2.505     2.505     2.505       2.51   89.26
  4        -3.84615       -9.744    -9.745    -9.745      -9.74   90.75
  5        -3.84615        5.052     5.051     5.049       5.05   88.74
  6        -3.84615        9.287     9.287     9.287       9.29   90.24
  7        -3.84615       15.150    15.150    15.149      15.15   88.29
  8        -3.84615      -10.788   -10.788   -10.788     -10.79   88.61
  9        -3.84615       -1.304    -1.305    -1.306      -1.30   89.68
 10        -3.84615       -2.178    -2.179    -2.180      -2.18   89.36
 11        -3.84615       -5.007    -5.007    -5.007      -5.01   89.43
 12        -3.84615       -2.869    -2.869    -2.870      -2.87   89.40
 13        -3.84615      -11.667   -11.667   -11.667     -11.67   89.99
 14        -3.84615      -17.998   -17.998   -17.998     -18.00   89.38
 15        -3.84615      -11.519   -11.519   -11.519     -11.52   88.52
 16        -3.84615       -8.259    -8.259    -8.259      -8.26   89.19
 Processing file:  /home/wera/data/koolina/fullcal/20031500013_koo.cal

 ......< snip >.....

 Processing file:  /home/wera/data/koolina/fullcal/20031500512_koo.cal
 t_sweep  =    0.26000 s
 mt       =        768 samples
 nfft     =        256 samples
 nant     =         16 antennas
 i_offset = 1521134307 DDS steps
 f_offset = -980.76927 Hz
 Antenna:   DC values [V]:        RMS values: [V]       Cal values:
  1         0.00878    0.01204    3.87157    4.00753    1.13505    1.09654
  2         0.01314    0.01176    4.09569    4.04764    1.07294    1.08568
  3         0.01309    0.00764    3.80786    3.78605    1.15404    1.16069
  4         0.01208    0.01177    4.35519    4.39443    1.00901    1.00000
  5         0.00920    0.00557    4.09562    4.12849    1.07296    1.06442
  6         0.00745    0.01284    3.93506    3.93083    1.11674    1.11794
  7         0.01639    0.01294    3.69495    3.70416    1.18931    1.18635
  8         0.01145    0.01232    3.99788    4.07031    1.09919    1.07963
  9         0.01083    0.00332    3.82736    3.86516    1.14816    1.13693
 10         0.02284    0.01465    4.18160    4.09042    1.05090    1.07432
 11         0.02094    0.01581    3.96858    4.08938    1.10731    1.07460
 12         0.01281    0.01047    3.58419    3.56948    1.22606    1.23111
 13         0.01276    0.01396    3.99718    3.89523    1.09938    1.12816
 14         0.02358    0.02429    3.88712    3.89639    1.13051    1.12782
 15         0.00723    0.01230    3.93370    3.96633    1.11712    1.10793
 16         0.00595    0.00611    3.90962    4.04590    1.12401    1.08615
 Antenna: Freq.:    Phase: Peak-1    Peak     Peak+1       LSQ   I/Q-Balance
  1      -980.76923        0.000     0.000     0.000       0.00   93.07
  2      -980.76923      -12.602   -12.602   -12.602     -12.60   87.85
  3      -980.76923       -0.342    -0.341    -0.341      -0.34   89.89
  4      -980.76923      -27.292   -27.292   -27.291     -27.29   90.55
  5      -980.76923        2.083     2.083     2.083       2.08   88.83
  6      -980.76923        5.382     5.383     5.383       5.38   89.69
  7      -980.76923       13.187    13.187    13.187      13.19   88.59
  8      -980.76923      -13.885   -13.884   -13.884     -13.88   94.05
  9      -980.76923       -7.162    -7.162    -7.162      -7.16   89.32
 10      -980.76923      -13.930   -13.930   -13.930     -13.93   75.38
 11      -980.76923       -9.760    -9.760    -9.759      -9.76   93.16
 12      -980.76923      -23.722   -23.722   -23.722     -23.72   89.01
 13      -980.76923      -12.709   -12.708   -12.708     -12.71   88.93
 14      -980.76923      -33.995   -33.994   -33.994     -33.99   89.32
 15      -980.76923      -15.356   -15.355   -15.354     -15.35   85.54
 16      -980.76923       -8.791    -8.790    -8.790      -8.79   90.72
 Calibration data in
 /home/wera/data/koolina/fullcal/20031500010_koo.cal.amphase
 To activate this calibration, please execute the command:
 > cp /home/wera/data/koolina/fullcal/20031500010_koo.cal.amphase /home/wera/etc/calibration.wera 

Remark: Existing measurements which only used /home/wera/etc/calibration.wera can be 
improved by connecting the  Calibration Box with short cables to the receiver inputs 
(even after the measurement campaign in the lab if no receiver modules have been exchanged/replaced). 
In this case, only the /home/wera/etc/<sitename>.fullcal (see below) file should be used; 
do not cp /home/wera/data/koolina/fullcal/20031500010_koo.cal.amphase /home/wera/etc/calibration.wera

 FullCalibration data in
 /home/wera/data/koolina/fullcal/20031500010_koo.cal.fullcal
 To activate this FullCalibration, please execute the command:
 > cp /home/wera/data/koolina/fullcal/20031500010_koo.cal.fullcal /home/wera/etc/<sitename>.fullcal

 > cp /home/wera/data/koolina/fullcal/20031500010_koo.cal.fullcal /home/wera/etc/koolina.fullcal

Like Plott_WERA_Cal_lsq, the output of the program gives information on: 

t_sweep:      Duration of the frequency chirp [s]
mt:           Number of samples within a chirp
nfft:         Number of chirps
nant:         Number of antenna channels
i_offset:     Offset in DDS steps between receive and transmit frequency 
              to generate a constant offset signal for calibration.
              124076836 DDS steps transform to -80.00000 Hz, which 
              corresponds to a signal arriving from range cell 20.
              This offset is increased by the equivalence of 
              1 range cell from data run to data run.
f_offset:     Offset frequency calculated from i_offset.

A list of DC values, RMS values and Cal values follows for each antenna:
------------------------------------------------------------------------
DC values  [V]: DC measured from the I and Q channels in Volts
RMS values [V]: RMS of signal measured from the I and Q channels in Volts
Cal values    : Multiply each channel with this value to compensate for
                gain differences. (Needed for the calibration file)

A list of Peak frequency, Phases relative to antenna #1 and I/Q balance follows:
--------------------------------------------------------------------------------
Freq.:         Peak frequency identified by a FFT.
Phase Peak-1:  Phase relative to antenna #1 measured by FFT 
               one spectral line left (negative) of the peak identified.
Phase Peak:    Phase relative to antenna #1 measured by FFT
               at the peak identified.
Phase Peak+1:  Phase relative to antenna #1 measured by FFT
               one spectral line right (positive) of the peak identified.
LSQ:           Phase relative to antenna #1 measured by a Least Squares Fit.
	       This value is used during normal measurements to force back all 
               channels to pase Zero. (Needed for the calibration file)
I/Q-Balance:   Phase difference between I and Q, should be 90 degrees.

Graphics output can be generated by Plott_WERA_FullCal 

Linux:

Source is in wera_fullcal_lsq.F
Compilation and linking with '. do_wera_fullcal_lsq.sh'

Call with 
> wera_fullcal_lsq <first_calibration_file>.cal <last_calibration_file>.cal  e.g.:
> wera_fullcal_lsq ~/data/koolina/fullcal/20031500010_koo.cal ~/data/koolina/fullcal/20031500512_koo.cal


VMS:

Source is in WERA_FullCal_lsq.F
Compilation and linking with '@WERA_FullCal_lsq'
Program needs to be defined as an external command to take parameters
from the command line, e.g.
$ WERA_FullCal_lsq :== $$USER1:[WERA.Fortran]WERA_FullCal_lsq.exe

Call with
$ WERA_FullCal_lsq <first_calibration_file>.cal  <last_calibration_file>.cal    e.g.:
$ WERA_FullCal_lsq $DATA1:[WERA.Fortran]20013411230_hmb.CAL $DATA1:[WERA.Fortran]20013411730_hmb.CAL

Comments to: gurgel@ifm.uni-hamburg.de (Klaus-Werner Gurgel)