COFDM modulator SFN

COFDM-modulator SFN
Appearance of COFDM-modulator SFN

* For use in the set of transmitting equipment in the organization multifrequency (MFN) and single frequency (SFN) networks over-the-air   digital television broadcasting standards DVB-T and DVB-H (mobile broadcasting)
* It effects shaping of a high-frequency signal with a QPSK modulation (and reception of these very signals) according to
  the EN 300 421 (DVB-S) standard for primary distribution networks
* Shaping of a high-frequency signal with a COFDM modulation according to the EN 300 744 (DVB-T/H) standard for a secondary   network according to the TS101191
* The SFN operates in three modes:
  1) Multifrequency network (MFN mode)
  2) Master of single frequensy network (SFN-Master mode)
  3) Slave of single frequency network( SFN-Slave mode)
* Control: local or via an Ethernet network
* Technical description and manual (1547 kb)

Specifications of a primary distribution network (Radio relay link)
Modulator QPSK Output IF signal level -24 dBm @ 30 MHz
IF signal level frequency 70 MHz
Internal coding Convolutional coding К=7 (171, 133)
Coding rate 2/3
External coding Reed-Solomon (204, 188, Т=8)
Randomizer/Interleaver Convolutional/ I=12
Modulation kind QPSK
Symbol rate 27 Msps
Receiver QPSK Input signal level -65...-25 dBm
Operating frequency range 950...2150 MHz
Input frequency step 1 MHz
Modulation kind QPSK
Input resistance 75 Ω
Coding rate 2/3
Symbol rate range 3.3...29.9 Msps
Converter Transfer ratio -14 dB
Operating frequency range 950...2150 MHz*

* Due to the fact that the output of the COFDM modulator SFN on IF2 a filter with a bandwidth of 30 MHz, the frequency IF2 installed at the manufacturer's.

Specification of Secondary distribution network (DVB-T)
Modulator (4) Output IF signal level -20 dBm @ 8 MHz
IF signal level frequency 36 MHz
RF output signal level -20 dBm @ 8 MHz
RF signal frequency 470...862 MHz
Internal coding Convolutional coding К=7 (171, 133)
Coding rate 1/2, 2/3, 3/4, 5/6, 7/8
External coding Reed-Solomon (204, 188, Т=8)
Randomizer/Interleaver Convolutional/ I=12
Guard interval 1/4, 1/8, 1/16, 1/32
Modulation kind QPSK, QAM16, QAM64
Modulation mode 2k, 8k, 4k
Long-term transmission frequency stability 1*10Е-9

GPS receiver specifications
Adjustment frequency L1 1.57542 GHz
Input signal level -130...-100 dBm

Common specifications
Time of sync circuit start in operation mode (COFDM transmitter frequencies in points A and B differentiate in 1 Hz, not more) <=15 min
Voltage supply/Consumption current 220 ± 30V / 0,2A
Dimensions 1U(19")483x260x44 mm
Weight 5 kg

The term Primary Distribution Network means relay transfer/reception of an integrated transport stream TS in/into different destination points.

The term Secondary Distribution Network means DVB-T/H signal shaping and transmission (COFDM-8k) with a 1 Hz frequency difference in various destination points with time delay compensation occurring in a primary distribution network and coincident symbol shaping and distribution at the same moment in the indicated destination points (because time delay compensation is a necessary but not a sufficient condition of coincident symbol shaping).

An SFN structure scheme is given in fig.1.

SFN-1.jpg

Shorthand names of units:
    1 - GPS synchronizer reference frequency;
    2 - QPSK receiver;
    3 - control block;
    4 - COFDM modulator;
    5 - SFN unit for transport stream adaptation;
    6 - QPSK modulator;;
    7 - QPSK converter mixer;
    8 - QPSK converter output filter;
    9 - heterodyne oscillator of QPSK converter;

An MFN structure scheme is given in fig.2.

SFN-3-e.jpg

Modulator COFDM SFN mode MFN (the key in the middle position) received on the ASI-input formed transport stream and then he goes to the input of the modulator COFDM. High-frequency signal from the output of the modulator COFDM, on the UHF frequency range, is fed directly into the secondary distribution network, ie the digital TV transmitter.

A single-frequency network arrangement in points A and B (see fig.2).

SFN-2.jpg