Spectrographic Analysis

The NEXTWave Signal Processing Lab data analysis software includes a powerful spectrogram display with user-adjustable parameters that allows for in-depth analysis of a signal.  The NEXTWave SPL spectrograph serves as a sophisticated data analysis tool in which the user can easily work with real-world signals.

Spectrogram Analysis with NEXTWave SPL

Several signal examples are shown on a NEXTWave SPL spectrogram.

Leonid meteor and satellite radar echoes

Here a spectrographic analysis of a radar echo is made so as to observe the differences between the frequency signatures of a meteor and a satellite.

Because meteroids move at higher velocities than low Earth orbit satellites the Doppler shift from a meteoroid echo is greater than that of a satellite. However, the radar echo recorded is caused by a bounce off of the ionized air that is left behind when the meteoroid disintegrates in the atmosphere, and not the meteoroid itself. The low velocity of the ionized trail results in no observable Doppler shift in the meteor echo which is shown in the spectrogram as a nearly horizontal line with no drift in frequency.  The satellite reflection is seen as a near-vertical line.


An acoustic spectrographic analysis can be a useful aid in the study of animal sounds and communications.  In this example the song pattern of a Tree Pipit bird call is observed.  Sections of the waveform can easily be isolated and generated via digital-to-analog conversion (DAC) so that the region of interest can be heard.

 

Analysis of a Tree Pipit bird call

Saturn radio emission detected by Cassini spacecraft

Saturn is a source of intense radio emissions. The radio waves are closely related to the auroras near the poles of the planet. These auroras are similar to Earth's northern and southern lights.

In the spectrogram shown here it appears as though the three rising tones are launched from the more slowly varying narrowband emission. This may represent a very complicated interaction that occurs between waves in Saturn's radio source region, but one which has also been observed at Earth.

http://www.nasa.gov/123160main_cas-skr2-072504.wav