PROMAX MO-270 User Manual

The MO-270 is a DTMB modulator compliant with China’s
national standard specification for digital terrestrial
broadcasting GB20600-2006. The input to the modulator
is an MPEG-2 Transport Stream (TS) in SPI or ASI
formats. The output from the unit is a TDS-OFDM
modulated DTMB signal upconverted to IF or RF.

The modulator has been designed to achieve the
maximum performance yet at an affordable price.
The digital coding and modulation process is
implemented with programmable logic devices
using PROMAX proprietary IP. This makes the design
highly flexible, allowing to tailor it to any particular
application.

DMTB Modulator General overview

The MO-270 is a general purpose DTMB modulator con­tained in a 19” 1U chassis. The unit has three selectable
MPEG-2 TS inputs (two serial ASI inputs and one parallel
SPI input). An additional test TS can be generated inter­nally in the modulator. This allows to generate compliant
DTMB signals even in the absence of a valid TS input.

The MO-270 is able to work with any incoming bit rate as
long as this is strictly lower than the value given in the
DTMB specification for the modulation parameters in use.
The input TS bit rate is adapted (bit rate adaptation) to the
useful bit rate required by the DTMB signal by stuffing the
TS with NULL packets (packet stuffing). This stuffing pro­cess alters the sequence of PCR values embedded in the
TS. These values have to be re-stamped to minimise the
PCR jitter remaining after packet stuffing.

The modulator can be configured to generate any of the
transmission modes listed in the DTMB specification.
Several test modes are available in the MO-270 (blanking
of carriers, single tone output, test TS generation).
The modulator is frequency agile. The user can select an
RF output frequency between 45 and 875 MHz in steps of
1 Hz. The polarity of the IF/RF spectrum (inverted or non­inverted) can be selected by the user.

The operation of the MO-270 is controlled via the front
panel LCD display and controls. The modulator can be
easily configured by navigating through a rather intuitive
set of menus.

Detailed description

DTMB MODULATOR

MO-270

Two transport stream ASI inputs, one SPI input

Seamless automatic switching between ASI inputs

TDS-OFDM (1 or 3780 subcarriers) modulator compliant with China
national standard GB20600-2006

High MER Noise generator

(optional)

Channel simulator
(optional)

Frequency agility (1 Hz step), from 45 to 875 MHz

(*): DVB-H operation available as an option

DTMB MODULATOR

MO-270

PROMAX ELECTRONICA, S.A.

Francesc Moragas, 71 * 08907 L’HOSPITALET * SPAIN
Tel: [phone] * Fax: [phone] * [e-mail] * www.promax.es

SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE

SPECIFICATIONS MO-270

INPUTS

MPEG-2 Transport Stream inputs Two ASI inputs, female BNC, 75 Ω

One SPI input, LVDS DB-25

TS packets of length 188 or 204 bytes (automatic detection)

Support for burst and continuous packet mode

Input TS bit rate strictly below the value given in the DTMB specification.

Packet stuffing for bit rate adaptation and PCR re-stamping are carried out automatically

OUTPUTS

36 MHz IF output 50 Ω BNC female connector.

0 dBm average power

Normal or inverted spectrum

In-band amplitude ripple (to be defined)

Out-of-band spectral characteristics (to be defined)

Central carrier suppression (to be defined)

High MER

RF output 50 Ω BNC female connector

Frequency adjustable between 45 and 875 MHz in 1 Hz steps

Spectrum polarity selectable via the front panel controls

Average power level: From an approximate minimum of 80 dBµV down to 15 dBµV in steps of 1 dB

High MER

Auto muting in the presence of errors

DTMB PARAMETERS

Modulation TDS-OFDM, 1 or 3780 subcarriers
FEC 0.4, 0.6, 0.8
Constellation 4QAM-NR, 4QAM, 16QAM, 32QAM, 64QAM
Time interleaving 240 or 720 symbols
Guard intervals 1/4, 1/6, 1/9

TEST MODES

Blank a number of carriers (start index to stop index)

Generate a single carrier at the central frequency whose level equals the

average TDS-OFDM output power. This is intended for signal level alignment

Test Transport Stream packet generation using PRBS sequences of length 15 or 23 bits

carried within NULL packets

CONTROL INTERFACE

Pushable rotary control on the front panel with navigation key and LCD display

Two LEDs indicate the power and synchronisation status of the equipment

Ethernet RJ-45 connector

MECHANICAL SPECIFICATIONS

Dimensions 19” wide 1U high rack chassis

Width × Height × Depth = 19” × 1.75” × 15”