суббота, 23 июля 2011 г.

Updating SA to the version v 6.2.5.4.

Updating SA to the version v 6.2.5.4.

This is planned update SA. We had added function of inversion of the whole spectrum at once. This function, in difference from regular procedure, works much more quickly. Very often similar problems arise at the analysis of various I/Q (SDR) records.




At coincidence/combination of H-markers and a call of the regular procedure of in-band inversion, the special case of fast inversion of the whole spectrum is working.


 ***
 two popular enough in analysis functions ACF and CCF are introduced into module WF. Basically, it duplicates similar decisions in the basic working window, but for the module of the form of a signal, this opportunity is far not superfluous.




Please pay attention, that the result of ACF function is displayed in the new window.






The result of function CCF is mapped in the same window, whence the function has been caused. Thus, the basic signal is mapped as a background, and the working element of the window is function CCF, its graphic is scaled, displaced, etc. the Segment/fragment of a signal, which is chosen as example for calculation CCF, is painted in yellow color.


*** 
The work with long symbols (up to 32000 samples (LS) and higher) is provided in module OFDM. The previous versions had restriction in 9000-10000 samples. However, it is necessary to notice, that analysis of OFDM signals with such sizes LS (~ 16000-20000 samples), demands certain, sometimes essential expenses of time.


As usual, a number of internal small (sometimes even funny) bugs, which had been found out by users are eliminated. To a category of the "funny bugs", we bringh a recent turn of image CT, in this version all is returned on former positions.:-) actually, both variants are correct. But as, the left part at us has been proved as "good" in one of early SA articles - "work with module OFDM, FFT spectrum", we decided to return to a former format of CT display.

Good Luck ~

среда, 13 июля 2011 г.

OFDM. COFDM: Rohde&Schwarz GN2130 digital voice modem

Rohde&Schwarz GN2130 digital voice modem
OFDM, Ch - 48, Sh - 56.25, Br - 44.4(4), QAM-16/PSK-4, k = 17/64

Author: SergUA6 
Band Width ~ 2700 Hz
Low Range ~ 360 Hz
Baud Rate 44.4(4) Hz
n-Ary (PSK/MPSK) Mixed QAM-16/PSK-4
Count of Carriers 48
Step between carriers 56.25 Hz
ACF Typical ~ 45 ms
RX mode  SSB




Sonorgams:

pic.1  General view


Diagrams:

pic.2 General quantity of the channels



pic.3 The constellation in the channel




R&S GN2130 - is the The voice modem, optionaly delivered to HF transceiver XK200 of R&S corporation. It is used for a speech transmission after conversions into a digital form, closing of the data by means of internal cryptoprocessor is possible. In this example, 48 channel OFDM signal is orginized, with standard enough parametres. 


Modulation in the channels is mixed QAM-16/PSK-4.  Features: it is necessary to mark presence of the auxiliary/pilot-symbols , in every second symbol through every one channel for synchronisation and customisation/fine tuning of the adaptive corrector the special signals are transmitted. Also there is a presence of the preamble with duration about 600 msec. Maximum common technical speed for QAM-16 is ~ 8533 bps.