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RADARDECODE
Section: Misc. Reference Manual Pages (1L)
Updated: 16 August 1999
Index
Return to Main Contents
NAME
radardecode - decode radar data (ao)
SYNOPSIS
radardecode
[
-dqrt
]
[
-b
bits
]
[
-c
codelen
]
[
-l
decodeFftlen
]
[
-n
numcodes
]
[
-o
offset
]
[
-p
numPol poltoUse
]
[
-s
samplesPerBaud
]
[
-m
machine
]
[
-f
freqShift_NotYetImplemented
]
DESCRIPTION
radardecode
is a filter to decode radar data.
The overlap save algorithm from THE FAST FOURIER TRANSFORM AND ITS
APPLICATIONS (Brigham 1988 pg.212) is used.
The input data is read from standard input (as a pipe), unpacked,
transformed to the frequency domain, conjugated and then multiplied by the
transformed code, transformed back to the time domain, and then the complex
points are written to standard out as two 4 byte floating point numbers.
radardecode
on startup will first allocate the buffers it needs and then it prepares the
pn code.
The program
/usr/loca/bin/comppncode
will be run to generate the pn code to use for decoding.
The input data can be ri, cbr, or unpacked data (depending on
the -m option).
The program will only process one polarization at a time.
If ri data is input, then the header must have been already
be stripped off (see stripVme(1l).
If the ri data had two polarizations, then one of them must
be stripped off before inputting it to this program.
If cbr data is input then all polarizations are input to the
program and the -p option is used to tell the number of
polarizations input, and which polarization should be
decoded.
For unpacked data, the input should be complex floating point
numbers (one polarization only).
A number of shell scripts under
~phil/datatk/astro/rdrN
have been written to drive the
radardecode
program (see
radarranging(1l)).
OPTIONS
- -b
-
bits
The number of bits the data was sampled at.
It can be 1,2,4,8 or 12.
The default is 12 bits.
cbr and unpacked data ignore this value.
- -c
-
codelen
The codelen for the pn code that was used.
The default is a codelength of 2047.
- -l
-
fftlength
This is the length of the transform to use for decoding.
The default fft length is 32k.
- -n
-
numcodes
The number of codes of length
codelen
to decode.
The program will decode the data until the this many codes have been
decoded or the end of the input data stream is hit (whichever comes first).
The default value is 100000000 codes.
- -o
-
offset
Offset to add to the input data.
The ri two's complement packing of the sampled data goes from -m to (m-1).
To give zero dc bias you would normally add .5 to the input data so the
positive and negative numbers are symmetric about zero.
This value will not be added to the pn code that is input.
The default is to add no value to the input data.
- -p
-
numPol polToUse
For cbr data this specifies the number of polarizations in the input
data and which polarization to use on output.
The default is numPol == 2 and polToUse == 1.
- -q
-
Run quietly.
Do not output how many ffts have been done so far.
The default is to output to
stderr
how many ffts have been done (every 50 ffts).
- -r
-
Remove DC.
If this option is selected then the mean will be computed and removed
for each fftlength complex points.
The default is to not remove DC.
- -s
-
samplesPerBaud
This can be any integer number >= 1. It will duplicate each baud in
the code by this value before decoding.
The default value is 1.
- -m
-
ri cbr unpacked
The type of data input.
The default is the ri.
If cbr is selected, then
the -p option should be used to specify the polarization info.
The default value is ri.
- -t
-
Print the times for each fft to
stderr
complex multiply, fft--> time domain, and output.
The default is to not output this information.
- -f
-
freqShift
Shift the frequency in the decoding process (in case there was
an ephemeris error).
This is no yet implemented.
EXAMPLES
The examples below show different ways of calling
radardecode
Assume the data is from the ri and is on disc. The headers have
already been stripped off. The data is 2 bit packed, one polarization,
with a codelength of 8191.
Add .5 to the input data and don't printout the time for each fft.
Since the number of codes were not given, the program will decode until
the end of file is hit or 100000000 codes have been decoded.
-
radardecode -b 2 -c 8191 -l 131072 -o .5 < infile > outfile
Assume the data is ri 8 bit data on disc, two polarizations,
with the headers already removed.
You want to decode the 1st (oc) polarization.
The code is 2047 long and the decode fft length is 256k
-
selectpnts -b 4 -f 1 -s 2 | \ # remove 2nd pol
radardecode -b 8 -c 2047 -l 262144 -o .5
Decode cbr data, 2 polarizations, 2 samples/baud, and keep
the 1st polarization. The codelength is 64k-1.
The output data will have 65535*2 range bins.
-
radardecode -m cbr -p 2 1 -c 65535 -l 262144 < infile > outfile
FILES
~phil/util/filters/radardecode.c location of source code
/usr/S2local/bin/radardecode executable for sun
~phil/datatk/astro/rdrN/main_decode.sc shell scripts to drive radardecode.
/usr/local/bin/comppncode program to compute pncodes for sun.
SEE ALSO
comppncode(1l),radarranging(1l)
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- OPTIONS
-
- EXAMPLES
-
- FILES
-
- SEE ALSO
-
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