Difference between revisions of "Demodulator"

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A '''Demodulator''' (short '''Demod''') recovers (demodulates) the original information from the received and downconverted RF signal. In case of digital TV this is the [[MPEG2 Transport Stream]], in case of analogue TV the [[Wikipedia:Composite video|Composite Signal]].
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A '''Demodulator''' (short '''Demod''') recovers (demodulates) the original information from the received and downconverted RF signal -- a tuner acquires the RF signal and converts it to an intermediate frequency (IF) which is then passed onto the demodulator for processing. The type of demodulator IC used for this task of information recovery is specific and dependent upon the nature of the signal transmission scheme involved.  
  
Digital Demodulators also perform [[Wikipedia:Forward Error Correction|Forward Error Correction]] ([[Wikipedia:Convolutional Code|Convolutional Viterbi-]] and [[Wikipedia:Reed-Solomon_error_correction|Block-Reed-Solomon-Decoding]]).
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In the case of analog TV, the IF inputted into the demodulator contains the [[Wikipedia:Composite video|composite signal]] that was originally modulated onto the RF carrier.  After recovery, the demodulator outputs a CVSB signal, which will then need to be digitized through sampling techniques performed by a A/V decoder.  
  
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In the case of digital TV transmission schemes, the IF inputted into the demodulator contains a [[MPEG2 Transport Stream]] (TS) that was originally modulated onto the RF carrier.  In the process of recovering that TS, digital demodulators will perform [[Wikipedia:Forward Error Correction|Forward Error Correction]] ([[Wikipedia:Convolutional Code|Convolutional Viterbi-]] and [[Wikipedia:Reed-Solomon_error_correction|Block-Reed-Solomon-Decoding]]).  This whole process is sometimes referred to as RF-to-bits, for, unlike the case with analog IF demodulators, the recovered signal outputted from the digital demodulator is already a digital bit stream; specifically a TS.  The TS will in turn be sent to a decoder  in order to display (and, depending upon what format the underlying video content contained within the TS was encoded with, this could be a MPEG2 or MPEG4 decoder ... and either [[Hardware or Software Decoder?|hardware or software based]]).
  
{| border="1" cellpadding="5" cellspacing="0" align="center"
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==Also see==
|+'''Some Examples for Digital Demods are'''
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* [[Demodulator Chipsets]]
|-
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! style="background:#ffdead;" | Model
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! style="background:#ffdead;" | Type and Vendor
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|-
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! style="background:#efefef;" | [[NXT6000]]
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! [[DVB-T]]/[[COFDM]] Demod produced by [[ATI/AMD|ATI]]
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|-
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! style="background:#efefef;" | [[Atmel AT76C651|AT76C651]]
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! [[DVB-C]]/[[QAM]] Demod produced by [[Atmel Corporation]]
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|-
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! style="background:#efefef;" | [[Conexant CX22700|CX22700]]
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! [[DVB-T]]/[[COFDM]] Demod produced by [[Conexant Systems, Inc.]]
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|-
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! style="background:#efefef;" | [[Conexant CX24110|CX24110]]
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! [[DVB-S]]/[[QPSK]] Demod produced by [[Conexant Systems, Inc.]]
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|-
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! style="background:#efefef;" | [[DIB3000M]]
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! [[DVB-T]]/[[COFDM]] Demod produced by [[DiBcom]]
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|-
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! style="background:#efefef;" | [[LSI L64781|L64781]]
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! [[DVB-T]]/[[COFDM]] Demod produced by [[LSI Logic Corporation]]
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|-
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! style="background:#efefef;" | [[LSI L64782|L64782]]
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! [[DVB-T]]/[[COFDM]] Demod produced by [[LSI Logic Corporation]]
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|-
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! style="background:#efefef;" | [[Microtune MT8872|MT8872]]/[[SPaSE SP8872|SP8872]]
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! [[DVB-T]]/[[COFDM]] Demod produced by [[Microtune]]/[[SPaSE]]
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|-
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! style="background:#efefef;" | [[Philips TDA10021|TDA10021]]
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! [[DVB-C]]/[[QAM]] Demod produced by [[Philips Semiconductors]]
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|-
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! style="background:#efefef;" | [[Philips TDA10045|TDA10045]]
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! [[DVB-T]]/[[COFDM]] Demod produced by [[Philips Semiconductors]]
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|-
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! style="background:#efefef;" | [[Philips TDA10046|TDA10046]]
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! [[DVB-T]]/[[COFDM]] Demod produced by [[Philips Semiconductors]]
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|-
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! style="background:#efefef;" | [[Philips TDA8083|TDA8083]]
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! [[DVB-S]]/[[QPSK]] Demod produced by [[Philips Semiconductors]]
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|-
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! style="background:#efefef;" | [[SPaSE SP8870|SP8870]]
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! [[DVB-T]]/[[COFDM]] Demod produced by [[SPaSE]]
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|-
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! style="background:#efefef;" | [[STMicroelectronics STV0297|STV0297]]
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! [[DVB-C]]/[[QAM]] Demod produced by [[STMicroelectronics]]
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|-
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! style="background:#efefef;" | [[STMicroelectronics STV0299|STV0299]]
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! [[DVB-S]]/[[QPSK]] Demod produced by [[STMicroelectronics]]
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|-
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! style="background:#efefef;" | [[VLSI VES1893|VES1893]]
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! [[DVB-S]]/[[QPSK]] Demod produced by [[VLSI Technology]]
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|-
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! style="background:#efefef;" | [[VLSI VES1993|VES1993]]
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! [[DVB-S]]/[[QPSK]] Demod produced by [[VLSI Technology]]
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|-
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! style="background:#efefef;" | [[VLSI VES1820|VES1820]]
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! [[DVB-C]]/[[QAM]] Demod produced by [[VLSI Technology]]
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|-
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! style="background:#efefef;" | [[Zarlink MT312|MT312]]
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! [[DVB-S]]/[[DSS]]/[[QPSK]] Demod produced by [[Zarlink Semiconductor]]
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|-
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! style="background:#efefef;" | [[Zarlink MT352|MT352]]
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! [[DVB-S]]/[[DSS]]/[[QPSK]] Demod produced by [[Zarlink Semiconductor]]
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|-
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! style="background:#efefef;" | [[Zarlink ZL10312|ZL10312]]
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! [[DVB-S]]/[[DSS]]/[[QPSK]] Demod produced by [[Zarlink Semiconductor]]
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|-
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! style="background:#efefef;" | [[Zarlink ZL10313|ZL10313]]
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! [[DVB-S]]/[[DSS]]/[[QPSK]] Demod produced by [[Zarlink Semiconductor]]
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|-
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|}
+
 
+
 
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* [[Afatech AF9005]]
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* [[Afatech AF9015]]
+
  
 
[[Category:Technology]]
 
[[Category:Technology]]
 +
[[Category:Hardware]]

Revision as of 01:39, 19 December 2007

A Demodulator (short Demod) recovers (demodulates) the original information from the received and downconverted RF signal -- a tuner acquires the RF signal and converts it to an intermediate frequency (IF) which is then passed onto the demodulator for processing. The type of demodulator IC used for this task of information recovery is specific and dependent upon the nature of the signal transmission scheme involved.

In the case of analog TV, the IF inputted into the demodulator contains the composite signal that was originally modulated onto the RF carrier. After recovery, the demodulator outputs a CVSB signal, which will then need to be digitized through sampling techniques performed by a A/V decoder.

In the case of digital TV transmission schemes, the IF inputted into the demodulator contains a MPEG2 Transport Stream (TS) that was originally modulated onto the RF carrier. In the process of recovering that TS, digital demodulators will perform Forward Error Correction (Convolutional Viterbi- and Block-Reed-Solomon-Decoding). This whole process is sometimes referred to as RF-to-bits, for, unlike the case with analog IF demodulators, the recovered signal outputted from the digital demodulator is already a digital bit stream; specifically a TS. The TS will in turn be sent to a decoder in order to display (and, depending upon what format the underlying video content contained within the TS was encoded with, this could be a MPEG2 or MPEG4 decoder ... and either hardware or software based).

Also see