IQDat files

IQDat files are a level-zero type data product that reflect the ADC voltages sampled at the radar site.

Naming Convenctions

Currently the common naming convention for IQDat files is:<3-letter abbreviation>.iqdat

SuperDARN radars routinely change operating frequency. Some operating modes use multiple frequencies, either at the same time, or by alternating between frequencies. As a result, some files from some radars include all records for all frequencies in the same file and other radars separate out the individual frequencies into separate files, designated by a channel letter in the file name:<3-letter abbreviation>.[a-d].iqdat

For example, on 2019-02-01 the King Salmon radar (KSR) was operating simultaneously on two channels as seen from the file names 20190201.0401.00.ksr.a.iqdat and 20190201.0401.00.ksr.b.iqdat. Each file contains data from a different frequency channel.


Sometimes modes like twofsound will write data into a single file. In this case the two frequencies are marked as two separate channels, denoted using the channel parameter. However, it is important to note that some SuperDARN radars have stereo capability (transmitting and receiving on 2 frequencies simultaneously), which was the original intended usage of the channel parameter.


IQDat files are composed of records that contain scalar and vector fields.


Field name Units Data Type Description
radar.revision.major None char Major version number of the radar operating system.
radar.revision.minor None char Minor version number of the radar operating system.
origin.code None char Code indicating origin of the data.
origin.time None string ASCII representation of when the data was generated.
origin.command None string The command line or control program used to generate the data.
cp None short Control program identifier.
stid None short Station identifier.
time.yr None short Year. None short Month number (not padded)
time.dy None short Day (not padded) hrs short Hour min short Minute. s short Second. μs short Microseconds
txpow kW short Transmitted power
nave None short Number of pulse sequences transmitted.
atten None short Attenuation level.
lagfr μs short Lag to first range
smsep μs short Sample separation
ercod None short Error code
stat.agc None short Automatic gain control status word.
stat.lopwr None short Low power status word None float Calculated noise from clear frequency search.
noise.mean None float Average noise across frequency band.
channel None short Channel number, used to denote different Tx/Rx channels on Stereo radars, and to denote changes in radar operating parameters between scans, eg. alternating between 2 frequency bands scan-to-scan
bmnum None short Beam number, zero based indexing
bmazm degrees float Beam azimuth
scan None short Scan flag.
offset None short Offset between channels for a stereo radar (zero for all others).
rxrise μs short Receiver rise time. s short Whole number of seconds of integration time. μs short Fractional number of microseconds of integration time.
txpl μs short Transmit pulse length.
mpinc μs short Multi-pulse increment.
mppul None short Number of pulses in sequence.
mplgs None short Number of lags in sequence.
mplgexs None short Number of lags used for tauscan. This field is stored for fit-level processing.
ifmode None short A flag indicating that the receiver voltage samples were obtained by digitizing the signal at an intermediate frequency (and then digitally mixed to baseband) instead of directly sampling the RF signals (ifmode=0).
nrang None short Number of ranges.
frang km short Distance to first range.
rsep rsep short Range separation.
xcf *None short XCF flag.
tfreq kHz short Transmitted frequency.
mxpwr dB int Maximum power.
lvmax None int Maximum noise level allowed.
iqdata.revision.major None int Major version number of the iqdata library.
iqdata.revision.minor None int Minor version number of the iqdata library.
combf None string Comment buffer.
seqnum None int Number of pulse sequences transmitted.
chnnum None int Number of channels sampled (both I and Q quadrature samples).
smpnum None int Number of samples taken per sequence.
skpnum None int Number of samples to skip before the first valid sample.


Field name Units Dimensionality Data Type Description
ptab None [mppul] short Pulse table.
ltab None [2,mplgs] short Lag table.
tsc s [seqnum] int Seconds component of time past epoch of pulse sequence.
tus μs [seqnum] int Microsecond component of time past epoch of pulse sequence.
tatten None [seqnum] short Attenuator setting for each pulse sequence.
tnoise None [seqnum] float Noise value for each pulse sequence.
toff None [seqnum] int Offset into the sample buffer for each pulse sequence.
tsze None [seqnum] int Number of words stored for this pulse sequence.
tbadtr None [seqnum] int
badtr None [2*mppul*seqnum] int
data None [totnum] int Array of raw I and Q samples.

The extent of each dimension is determined by the radar operating parameters. For example a value of mppul of 7 would result in the array ptab[7].

The raw sample data is arranged in multiplexed I and Q sample order; so the first smpnum*2 samples are the interleaved I and Q values for the first pulse sequence. If more than one channel is samples, the next smpnum*2 samples represent the next channel. The total number of samples, totnum, is equal to 2*seqnum*chnnum*smpnum.