Phase Analyzer
General description
The phase analyzer is a very powerful tool for signal phase analysis. In particular, different phase modulation types can easily be determined by using this tool as well as the IQ constellation display. It searches the transmission within the given frequency boundaries. Also you can set the decoded frequency by double clicking the left mouse button on the required frequency position.
When the transmission has been detected at some frequency within the given range, the decoder will then lock itself to that frequency. When locked, the decoder draws a bold blue line on the spectrum display at the currently locked frequency. If the decoder is not locked, then the blue line is not shown as bold. After locking the frequency, the decoder starts to plot the phase onto the display.
In the locked state, the carrier frequency is automatically monitored within the given frequency boundaries. If the carrier frequency changes, then the decoder moves to the new frequency. If 'Lock' is pressed in the user interface, then the decoder will not automatically change its frequency. ‘Reset’ resets the decoder and the received text can be saved by using ‘Save’
SkySweeper supports both FFT and waterfall display modes for decoder tuning. The Decoder Spectrum Dialog chapter gives more information about spectrum display options.
Configuration
When the ‘Config’ button is pressed, the following configuration dialog is opened.
Parameters
Tone Scan Area
The scanned frequency range is give two values - ‘low’ and ‘high’. The transmission is searched only within this frequency window. In most cases it is useful to firstly search the transmission visually using the spectrogram, FFT and 3DFFT displays and then define the scan area for the Phase Analyzer.
Carrier Fine Tune
This parameter is for fine-tuning the frequency. Accurate (coherent) tuning is needed to provide exact phase analysis so that the phase transitions etc. may be easily determined.
Bandwidth
This is analyzer internal filter bandwidth.
Downsampling
This is the downsampling ratio. If the ratio is N, then only every Nth signal sample is plotted on the screen.
Absolute phase
If this is selected, the phase is displayed as absolute phase. If this is not selected the phase is displayed as differential (the difference between consecutive samples)
Average
If this is selected the average phase is displayed.
History buffer size
This is the history buffer size of the phase display, in samples.
Scale
The ‘Y’ Scale of the phase display (either in degrees or radians).
