SA update to version v 6.2.5.0/1

SA update to version v 6.2.5.0/1

Planned SA update.

Determination of an exact amount of frequencies in the various MFSK signals is an important enough task in the analysis. In this update we had added this possibility, we introduced function "Count freqs” into the module of viewer of the form(WF).

The function "Count freqs" calculations of the size of the grid of frequencies. I underline, not an amount of frequencies used/involved in a current fragment of a signal, but dimensionality of the grid, in which limits these frequencies are generated.

Basic actions on function "Count freqs" usage are the following:

1. To receive speed of manipulation of the signal - Baud rate, by any method. It is desirable, but not a mandatory step.

2. To select the signal by H-markers. This operation demands an accuracy. It is impossible to select the signal too densely, and it is impossible to select it too widely, the reasonable compromise is required. Normally we recommend to allocate the markers on distance within (1.5-3) *Br from the signal.

3. Call the Phase detector function. It is the standard operation, which creates the new window with results.

4. It is necessary to call WF module in the new window through PopUp menu, it is also the standard action. If in the first point value Baud rate has been received, in WF module, then the automatic filtration of the signal will be produced, otherwise the filtration will be necessary to realize in the manual mode.

5. It is necessary that all artifacts (usually it is the beginning and the end of a signal) have been displayed behind the display window in WF module. It is possible to reach, at least by two methods:
The first - to select a pure part of the signal with V-markers, and to create a copy in the new window.
The second - using horizontal zoom, and shifting/moving the signal by the horizontal slider, to bring in the artefacts behind the window borders.

6. To turn on the mapping of the histogram "Sum"=ON on the "pure" signal. To pick up the size of the histogram by vertical. To install H-markers on the upper and lower channel of the histogram. To cause PopUp menu of the module. Position of V-markers can be any as all visible part of the signal is processed.

7. To select point "Count freqs".

Important! The result of function "Count freqs" is not an amount of channels in the signal, but the size of the uniform/proportional grid of frequencies, in which the used channels are "laid down". The so-called grid of formation, the size of this grid represents big interest in the analysis.

Range of determination of dimensionality of the grid of frequencies by the function "Count freqs", is from 4 to approximately 260. In reality, the function defines grids of more dimensionalities to 300-320, but it very strongly depends on the signal quality, and many other things.

Error report appearance is possible.

The reasons/causes:

- Both H-markers, and-or one of them, are installed not on the histogram lines/channels
- There are lesser then 4 or more then 400 frequencies in the signal
- The distance between H-markers is too small, or the markers are combined
- the function can't be completed correctly at current parameters of the signal, or on the current fragment of the signal.

There is an article on usage of this new function, as there are some thin moments and nuances, which are beyond the update description => Signals Analysis in SA version v 6.2.5.1

It is necessary to show certain care, although function "Count freqs" works reliably enough in many cases, nevertheless, it is rigid enough algorithm which can be mistaken.

As usual, minor problems found out by users are removed. Also I want to express gratitude to all beta testers, who have taken part in preliminary testing of this update.

Good Luck~

New Article: Perspectives of the analysis of OFDM signals with CP.

Perspectives of the analysis of OFDM signals with CP. 

As usual, we assume that reader possesses some basic knowledge concerning principles of formation OFDM, and the reader is acquainted with our previous articles, as terminology and the main ideas remain former. 

There are some general provisions. 

We already were being considered and showed in the previous articles, that at formation of OFDM signals the basic/main/key parameters are LS, LU and LG (CP), which are having dimensional samples. Basically, each one of these two parameters from these three (LS LU LG), unambiguously set the third parameter, as there is a simple correlation, namely: 

LS = LU + LG; 

We add one more, the dimensionless parameter, coefficient k = LG/LU or k = ((Sh/Br) - 1). This parameter allows to receive correct LS, LU and LG for specific conditions, besides k possesses mass of other remarkable properties, but it is beyond this article. 

In a general view the scheme of formation of OFDM signal with CP looks as follows: 

As we already considered, and I once again underline this moment, that there is no any Hertz and-or seconds! LS, LU and LG have at a stage of formation dimensionality of samples/samplings. We name it Fundamental/primary/key parameters of OFDM signal, these parameters are core of OFDM signal. All is equal to these parameters (samples), with what speed they will be transferred, needless to say, that transmission/transfer speed should be a constant.


As soon as some speed of following is given to samples (sampling rate of formation of OFDM signal OFDM), then earlier faceless values LS, LU and LG acquire/get dimensionality in Hertzs and-or seconds. But! They don't lose, and can't lose their main/fundamental properties. For example, as there was duration LS = 100, LU = 60 and LG (CP) = 40 samples, so it remains, irrespective of sampling rate.


There is one nuance in these transparent and logical enough conclusions. All what has been told above, concerns to so-called sampling rate of formation of OFDM signal.


In practice, to form a signal at once on operational frequency it is not convenient, and frequently it is not even possible. Normally, the signal should be formed on sampling rate Х, and further whole spectrum of the signal should be transferred on operational frequency Y. Thus, sampling rate X can't change duration LS, LU and LG, as it (sampling rate) is a consequence of existence of these parameters, and frequency of transfer Y can't destructively influence these parameters as it is not connected to them.


Let's sum up the told...


Full version of this article you may read here.


The arcitle contain examples on the real signals, schemes, detailed pictures, explanations and other interesting information.