DekTec DTE-3114 IP to 4x QAM - Manual (Page 5)

DTE-3114 – Networked Quad QAM Modulator
USER MANUAL
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selected QAM standard and mode. Channel filtering is applied and the resulting QAM-modulated
signal is digitally upconverted to an RF carrier in the VHF or UHF band.
The outputs of the four channels are added to each other, optionally with a plus or minus 3dB RF-
level correction per channel. The result is converted to analog, amplified with an adjustable gain
and put on the RF output. A second output with a fixed level is provided for monitoring purposes.
An embedded μP system (not shown in the functional block diagram) hosts a web and SNMP agent
to interface with the user or an SNMP network-management system. The control parameters are
stored in non-volatile memory and retrieved automatically after a power cycle.
1.3 Applications
Typical applications of the DTE-3114 include:
QAM test-signal generator
The DTE-3114 can be used as a standard QAM test-signal generator by using a PC to send a test
Transport Stream over IP to the DTE-3114. Typical uses include generating QAM signals in an R&D
environment, demonstration of QAM receiving equipment on exhibitions and production testing of
QAM-processing equipment.
Cable network simulator
The development of silicon tuners and line amplifiers requires simulation of fully loaded spectrum
conditions. Testing and debugging of Electronic Program Guide (EPG) and other software for QAM
set-top boxes or TV sets can benefit greatly from a multi-channel test signal that is under control of
the developer.
Such a simulation of a real cable network can be created by combining the output of multiple
DTE-3114s. For example, 64 channels can be created using 16 devices. It is not required to
generate a TSoIP stream for every RF carrier: Multiple channels can be configured to join the same
multicast group.
Small-scale CATV
A natural application for the DTE-3114 is as a high-density, low-cost QAM modulator in small-scale
cable television applications, for example in hospitals, student campuses or holiday parks. The MPTS
TSoIP streams can be generated by DekTec’s MuxXpert product running on standard PC servers.
1.4 Limitations
The structure of the hardware brings with it a number of limitations. The main limitations are listed
below.
Channel frequency Channels must be grouped: the overall output spectrum of the
DTE-3114 cannot be wider than 32Mhz.
Modulation standard All channels operate in the same mode, e.g. DVB-C, 256-QAM.
Symbol rate Range 4.48 - 7MBd. Each channel uses the same symbol rate.
RF level The RF level of the 4 channels must be positioned in a band of plus
or minus 3dB.