пятница, 24 июля 2009 г.

Chinese Mixed Mode (MFSK-4+OFDM-20/1) MFSK-4 Br-100, Shift-400 OFDM Br~72.2, Shift~100

The signal is here

Author: SergUA6 6.0

Band Width ~2200-2250 Hz
Low Range ~450 Hz, the shift is possible. Recieveing is in SSB
Baud Rate For MFSK ~100 Hz, For OFDM ~72.2 Hz
N-Ary (PSK/MPSK) mixed, pi/4 dqpsk and PSK-4
Count of Carriers For MFSK 4, for OFDM 20 + pilot
Step between carriers For MFSK ~400, for OFDM ~100 Hz
Pilot tones: spacing, frequencies (Pilot tone(s)) One pilot ~513 Hz, the shift is possible, Recieveing in SSB
The modulation in which the signal was recieved (RX mode) SSB


pic.1 the signal's generall look

pic.2 Manipulation speed for MFSK

pic.3 Manipulation speed for OFDM


pic.4 The graphical spectrum of the signal

pic.5 Detalization of the preamble


pic.6 Constellation of the upper channel OFDM

pic. 7 Constellation of the lower channel OFDM

Chinese Mixed(MFSK-4+OFDM-20/1) - Chineese modem. The classical OFDM signal with CP duration about ~ 3.85 msec. The interesting moment is that this signal is the classical OFDM with MFSK preamble. Nevertheless It is characteristic for China, and it is not big surprise. The record's quality is excellent, that allows to define easily all parametres of the signal with high reliability.