вторник, 11 мая 2010 г.

SA update version function of dynamic mapping of constellations in the selected channel

SA Update to version v
The current update is mainly concerned to OFDM module.

Some old control elements and indications are updated/moved: it is selected by the red frame.

Appearance of FFT spectrum is changed. Channels are separated by colour on both even and odd. The width of spectral lines is also increases with a graphic rescaling. It allows to select the necessary channel more comfortably. The former solution demanding absolutely exact hit in a line with the width in one pixel wasn't comfortable.

Perhaps the most important part of update - is an introduction of function of dynamic mapping of constellations in the selected channel, with the common clock/symbolical synchronisation.

In this mode, the programm carries out OFDM demodulation. At least, on the signals where relative phase manipulation is used, relative constellations can be observed practically irrespective of external factors, such as signal offset by frequency, record digitization etc.

An indication of an output of points of constellation behind the boundaries of mapping window is inserted. That speaks about necessity to reduce scale, as a constellation part, or the whole constellation is not displayed fully.

Basically, an order of standard operations in this module is the following:

- fragment of OFDM signal is selected in the working window.
- OFDM module is called/started.
- If it is necessary search of boundaries of a correlative triangle and customisation of other settings are installed. In most of cases, you may leave default settings.
- Start of search of a correlative triangle is realized by the button "Find CT"
- After a finding convincing Correlation Trianlge (CT), the signal's position should be adjusted by frequency. The triangle should be positive, and have maximum amplitude. It is controlled by the value of Am field in a window of mapping of triangle.
- After any frequency correction, recalculation is started again by the button "Find CT", as the signal is already another. Repeated calculations in this version are passing very fast, all subresults received earlier, are simply ignored.
- The yellow marker is located on the left ("good") side of a triangle.
- The necessary/convenient scale of FFT spectrum is installed, the necessary/needed channel is selected.
- phase planes are switched on by double-clique on the necessary record, in the window of output of the text data.
- The mode of dynamic mapping is started by button "Show".

It is the basic, generall scheme of operations.

Here is the Videoclip where on an example of signal MIL-STD-188-110A 16 Channels all described actions are shown.

The more detailed description of operation with the module as usually, will appear in the near future in the form of separate article.

Good luck~