Drake MEQ1000A Multiplexing Hybrid QAM Modulator - Manual (Page 6)

6 General Description
QAM O UT PU T
0.000 M bi ts/ S
ME Q1000A M UL TIPL EXI NG HY BRID QAM MOD UL ATOR
GENERAL DESCRIPTION
The R.L. Drak e m odel MEQ1000A is a comm ercial grade
hybrid QAM m odulator. The MEQ1000A features plug-in
input m odules that include an ATSC/QAM tuner, an ASI
input, an SDI/HD-SDI input, HDMI (non-HDCP), Com po-
s ite input, Com ponent input, and analog NTSC inputs;
thus the desc ription 'hybrid' is us ed to desc ribe it. A
m ultiplexer is built in to c om bine the trans port s treams
and input the filtered and groom ed trans port s tream to
the QAM m odulator. This m anual inc ludes feature ex-
am ples utilizing the Drak e DTD1000 Digital Tuner and
Dem odulator Module, and the ASII AS I- Input Module.
Other a vailable input modules inc lude:
SDE24 Dual SD MPEG Enc oder
HDE24 High Definiton MPEG Enc oder
SDI24A SDI/HD-SD I Input Enc oder
The MEQ1000A has tw o input m odule slots and the out-
puts interfac e to the MEQ1000A multiplexer, internally,
w here they are MPEG program filtered, m ultiplexed, and
groom ed. Programs , among the total group from input
m odule A and input m odule B, m ay be s elec ted or not
s elec ted by the operator to be s ent to the QAM m odula-
tor. Eac h input mus t c ontain no more than 20 programs
and a m axim um of 20 program s per input m ay be s elec t-
ed. Als o, the total bitrate of the s elec ted programs m us t
not exc eed that of the output QAM c hannel capacity.
Som e c ommon applic ations include: Channel Drop/Add,
c herry pic king program s from ASI MPTS inputs , digital
c hannel proc ess ing, or loc al origination additions .
The MEQ1000A c ontains a high perform anc e QAM m od-
ulator that c an operate in m os t ITU-A or ITU-B m odes up
through 1024QAM. The very low noise, high output, up-
c onverter pro vides c overage from 54 MHz to 1002 MHz
w hile m aintaining exc eptionally low phase nois e and
broadband nois e. Output level c an be s elec ted at a val-
ue between + 45 dBmV and + 61 dBmV.
The MEQ1000A operates in a fixed output c loc k mode
and proc ess es null pack ets when required to m aintain the
s et fixed c loc k rate. PCR c orrection is inc luded.
DIGITAL CH ANNEL PROCESSING (One input module)
The D TD1000 input m odule tunes any 8-VSB or QAM
c hannel betw een 54 MHz and 1002 MHz. It is ideal for
digital 'channel proc ess ing' applic ations w here a s ingle dig-
ital video s ignal is received, error c orrec ted, c lock ed at a u-
s er determ ined fixed rate and rem odulated on the s am e or
another RF c hannel. Applic ations inc lude cleaning up a
low MER QAM signal rec eived from a CATV s ourc e or fiber
link rec eiver, or
shifting the RF frequency of a QAM
m odulated s ignal. It m ay be us ed to c onvert one off-air ATSC 8-
VSB signal to a QAM output w ith rate adjus tm ent. Us ed in the
proc es sor mode w ith only one input, the MEQ1000 c an proc ess
ATSC or CA TV QAM inputs . No multiplexing or altering of any
MPEG tables is perform ed in this mode.
Us ed in the non-m ultiplexing m ode, the data rate of the inc om -
ing signal c an be any rate that falls w ithin the s pecific ation
range. The output rate c an be s et to any fixed output rate (e-
qual to or fas ter than the input rate).
MULTIPLEXING TWO ATSC TR ANSPORT STRE AMS
Utilizing tw o DTD1000 input m odules , tw o off-air 19.4 Mbps ATSC
s ignals (QAM m odulated CATV delivered s ignals c ould also be
us ed) c an be rec eived and m ultiplexed to obtain a 38.8 Mbps
256QAM output. Thus tw o ATSC inputs c an be output on a s ingle
6 MHz bandwidth 256 QAM channel.
Another way of c om bining tw o ATSC 19.4 Mbps s tream s is to
rec eive the firs t stream using the 8VSB input (DTD1000) and
input the s ec ond s tream , if available in ASI form at, through the
ASII m odule in the s ec ond input s lot. Again the tw o c ombined
ATSC s ignals will be m odulated at 256QAM in a 6 MHz w ide
c hannel. If it is desired to provide both ATSC s ignals from tw o
ASI s ourc es , tw o ASII m odules c an be us ed.
W hen the MEQ1000A is us ed as desc ribed above, no loss of
pic ture or s ound pack ets occ urs . There is no added c ompres sion
of the video or audio s treams . Only the nec ess ary c ontrol pack ets
are rew ritten to prevent duplic ation of MPEG2 program num bers
and m ajor and minor c hannel number ass ignments in the tables.
Us ing a PC interfac e, the operator c an s elec t the m ajor and m inor
program num bers that he des ires for eac h program in the output
m ultiplex.
PROGRAM FILTERING
A 'Selec t Program' func tion is provided to allow the operator to
s elec t w hic h of the MPEG program s pres ent on the A and B input
s tream s are to be inc luded in the output m ultiplex.
PSIP OPTIONS
W hen operating in the multiplex m ode, the MEQ1000A c an be s et
to proc ess PSIP inform ation from both s ourc es and rew rite tables
c ontaining c om bined PSIP inform ation, or in c ases w here the offair
broadc as t c hannels may not be transmitting s om e or all of the
tables , it can be set to ignore and disc ard the PSIP tables
c om pletely, or it c an be s et to generate MGT and VC T tables
w ithout EIT tables . Null pack et proc ess ing is applied as nec ess ary
to k eep the output data rate at the des ired s etting. PCR
c orrec tion is provided. The operator c an program des ired major
and m inor channel num bers for eac h program in the output
s tream .
OUTPUTS - RF and ASI
The 54 to 1000 MHz RF output is alw ays QAM regardless of
w hether the input is VSB or QAM. This s am e filtered s tream is
als o output via the rear panel ASI output jack .