hey guys, just wanted to know if any1 could please shred sum light on wat would the differnce in demodulation schemes of double side band suppressed carrier and single side band suppressed carrier. This is what i done with matlab coding for modulation and demodulation. 1. DSB-SC: - Modulation: (message signal 500hz) multiply by (carrier frequency 7000hz) ie: cos (2 pi 500 t) x cos (2pi7000t) = tx (transmission signal) Demodualtion: tx x PLL(phase lock loop) = 'c' Then i pass point 'c' through comb resonator. Adjust the output of signal after comb resonator for gain and get my message signal back. 2. SSB -SC Even though the modulation is different to DSB -SC, I'll try to describe it. YOu may have to draw a rough sketch to follow it. - m1(500 hz message signal) ((cos (2pi500t) x cos(2pi7000t) = 'd')) - 1st modualtion - (cos(2pi500t)x H(f)) x ((cos(2pi7000t x H(f)) = 'e' - 2nd modulation 'd' + 'e' = tx (1st modualtion + 2nd modulation = transmission signal). Note: i know H(f) is hilbert transfor and basically shift the signal 90 degrees making cos to sin. DEmodulation: Now to demodualte: the only scheme i can think of is goin to be same as the demodulate schceme for DSB-SC. I get the tx x PLL = 'c'. Pass this point 'c' through comb resonator, find gain and get my message signal. THIS IS WHERE I AM CONFUSED. WHAT HAVENT I CONSIDERED FOR THIS DEMOD SCHEME?? PLEASE HELP!!!

# Difference in demodulation of DSB-SC and SSB-SC

Started by ●November 13, 2006

Reply by ●November 13, 20062006-11-13

"10023101" <10023101@uts.edu.au> wrote in message news:RMGdnVYdmNIgsMTYnZ2dnUVZ_oSdnZ2d@giganews.com...> hey guys, just wanted to know if any1 could please shred sum light on wat > would the differnce in demodulation schemes of double side band suppressed > carrier and single side band suppressed carrier. This is what i done with > matlab coding for modulation and demodulation. >Learn to spell a little better first... M. -- Posted via a free Usenet account from http://www.teranews.com

Reply by ●November 14, 20062006-11-14

10023101 wrote:> hey guys, just wanted to know if any1 could please shred sum light on wat > would the differnce in demodulation schemes of double side band suppressed > carrier and single side band suppressed carrier. This is what i done with > matlab coding for modulation and demodulation. > > 1. DSB-SC: > > - Modulation: (message signal 500hz) multiply by (carrier frequency > 7000hz) ie: cos (2 pi 500 t) x cos (2pi7000t) = tx (transmission signal)Wot makes u tink dats suppressed carrier? It's straight AM.> Demodualtion: tx x PLL(phase lock loop) = 'c' > Then i pass point 'c' through comb resonator. Adjust the output of signal > after comb resonator for gain and get my message signal back. > > > 2. SSB -SC > Even though the modulation is different to DSB -SC, I'll try to describe > it. YOu may have to draw a rough sketch to follow it. > > - m1(500 hz message signal) ((cos (2pi500t) x cos(2pi7000t) = 'd')) - 1st > modualtion > - (cos(2pi500t)x H(f)) x ((cos(2pi7000t x H(f)) = 'e' - 2nd modulation > > 'd' + 'e' = tx (1st modualtion + 2nd modulation = transmission signal). > Note: i know H(f) is hilbert transfor and basically shift the signal 90 > degrees making cos to sin. > > DEmodulation: > Now to demodualte: the only scheme i can think of is goin to be same as > the demodulate schceme for DSB-SC. > > I get the tx x PLL = 'c'. Pass this point 'c' through comb resonator, find > gain and get my message signal. THIS IS WHERE I AM CONFUSED. WHAT HAVENT I > CONSIDERED FOR THIS DEMOD SCHEME?? > > PLEASE HELP!!!Du da math instead of assuming de ansa. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������

Reply by ●November 14, 20062006-11-14

>10023101 wrote: >> hey guys, just wanted to know if any1 could please shred sum light onwat>> would the differnce in demodulation schemes of double side bandsuppressed>> carrier and single side band suppressed carrier. This is what i donewith>> matlab coding for modulation and demodulation. >> >> 1. DSB-SC: >> >> - Modulation: (message signal 500hz) multiply by (carrier frequency >> 7000hz) ie: cos (2 pi 500 t) x cos (2pi7000t) = tx (transmissionsignal)> >Wot makes u tink dats suppressed carrier? It's straight AM. > >> Demodualtion: tx x PLL(phase lock loop) = 'c' >> Then i pass point 'c' through comb resonator. Adjust the output ofsignal>> after comb resonator for gain and get my message signal back. >> >> >> 2. SSB -SC >> Even though the modulation is different to DSB -SC, I'll try todescribe>> it. YOu may have to draw a rough sketch to follow it. >> >> - m1(500 hz message signal) ((cos (2pi500t) x cos(2pi7000t) = 'd')) -1st>> modualtion >> - (cos(2pi500t)x H(f)) x ((cos(2pi7000t x H(f)) = 'e' - 2ndmodulation>> >> 'd' + 'e' = tx (1st modualtion + 2nd modulation = transmission signal).>> Note: i know H(f) is hilbert transfor and basically shift the signal90>> degrees making cos to sin. >> >> DEmodulation: >> Now to demodualte: the only scheme i can think of is goin to be sameas>> the demodulate schceme for DSB-SC. >> >> I get the tx x PLL = 'c'. Pass this point 'c' through comb resonator,find>> gain and get my message signal. THIS IS WHERE I AM CONFUSED. WHATHAVENT I>> CONSIDERED FOR THIS DEMOD SCHEME?? >> >> PLEASE HELP!!! > >Du da math instead of assuming de ansa. > >Jerry >-- >Engineering is the art of making what you want from things you can get. >����������������������������������������������������������������������� >OK, I done the hand analysis and found out that i didnt consider the phase difference. Created a new demod scheme for SSB-SC. 1. tx x PLL = 'a' 2. 'a' x combresonator 1 = 'b' 3. 'a' x ( -180 degree phase shift x combresonator 2) = 'c' %the reasoning behind the -180 phase shift was the during modulation, the message signal was phase shifted 90 degrees and the ocsillator was phase shifted 90 degree as well. 4. 'b' + 'c' = 'd' %add the two streams of signal 5. 'd' x gain = (message signal acquired) Thx for kind and not so kind comments. Would love to hear your thoughts on this demod scheme.

Reply by ●November 14, 20062006-11-14

>>10023101 wrote: >>> hey guys, just wanted to know if any1 could please shred sum light on >wat >>> would the differnce in demodulation schemes of double side band >suppressed >>> carrier and single side band suppressed carrier. This is what i done >with >>> matlab coding for modulation and demodulation. >>> >>> 1. DSB-SC: >>> >>> - Modulation: (message signal 500hz) multiply by (carrier frequency >>> 7000hz) ie: cos (2 pi 500 t) x cos (2pi7000t) = tx (transmission >signal) >> >>Wot makes u tink dats suppressed carrier? It's straight AM. >> >>> Demodualtion: tx x PLL(phase lock loop) = 'c' >>> Then i pass point 'c' through comb resonator. Adjust the output of >signal >>> after comb resonator for gain and get my message signal back. >>> >>> >>> 2. SSB -SC >>> Even though the modulation is different to DSB -SC, I'll try to >describe >>> it. YOu may have to draw a rough sketch to follow it. >>> >>> - m1(500 hz message signal) ((cos (2pi500t) x cos(2pi7000t) = 'd'))->1st >>> modualtion >>> - (cos(2pi500t)x H(f)) x ((cos(2pi7000t x H(f)) = 'e' - 2nd >modulation >>> >>> 'd' + 'e' = tx (1st modualtion + 2nd modulation = transmissionsignal).> >>> Note: i know H(f) is hilbert transfor and basically shift the signal >90 >>> degrees making cos to sin. >>> >>> DEmodulation: >>> Now to demodualte: the only scheme i can think of is goin to be same >as >>> the demodulate schceme for DSB-SC. >>> >>> I get the tx x PLL = 'c'. Pass this point 'c' through comb resonator, >find >>> gain and get my message signal. THIS IS WHERE I AM CONFUSED. WHAT >HAVENT I >>> CONSIDERED FOR THIS DEMOD SCHEME?? >>> >>> PLEASE HELP!!! >> >>Du da math instead of assuming de ansa. >> >>Jerry >>-- >>Engineering is the art of making what you want from things you can get. >>����������������������������������������������������������������������� >> > >OK, I done the hand analysis and found out that i didnt consider thephase>difference. Created a new demod scheme for SSB-SC. > >1. tx x PLL = 'a' > >2. 'a' x combresonator 1 = 'b' > >3. 'a' x ( -180 degree phase shift x combresonator 2) = 'c' %thereasoning>behind the -180 phase shift was the during modulation, the messagesignal>was phase shifted 90 degrees and the ocsillator was phase shifted 90 >degree as well. > >4. 'b' + 'c' = 'd' %add the two streams of signal > >5. 'd' x gain = (message signal acquired) > >Thx for kind and not so kind comments. Would love to hear your thoughtson>this demod scheme. >

Reply by ●November 14, 20062006-11-14

>>10023101 wrote: >>> hey guys, just wanted to know if any1 could please shred sum light on >wat >>> would the differnce in demodulation schemes of double side band >suppressed >>> carrier and single side band suppressed carrier. This is what i done >with >>> matlab coding for modulation and demodulation. >>> >>> 1. DSB-SC: >>> >>> - Modulation: (message signal 500hz) multiply by (carrier frequency >>> 7000hz) ie: cos (2 pi 500 t) x cos (2pi7000t) = tx (transmission >signal) >> >>Wot makes u tink dats suppressed carrier? It's straight AM. >> >>> Demodualtion: tx x PLL(phase lock loop) = 'c' >>> Then i pass point 'c' through comb resonator. Adjust the output of >signal >>> after comb resonator for gain and get my message signal back. >>> >>> >>> 2. SSB -SC >>> Even though the modulation is different to DSB -SC, I'll try to >describe >>> it. YOu may have to draw a rough sketch to follow it. >>> >>> - m1(500 hz message signal) ((cos (2pi500t) x cos(2pi7000t) = 'd'))->1st >>> modualtion >>> - (cos(2pi500t)x H(f)) x ((cos(2pi7000t x H(f)) = 'e' - 2nd >modulation >>> >>> 'd' + 'e' = tx (1st modualtion + 2nd modulation = transmissionsignal).> >>> Note: i know H(f) is hilbert transfor and basically shift the signal >90 >>> degrees making cos to sin. >>> >>> DEmodulation: >>> Now to demodualte: the only scheme i can think of is goin to be same >as >>> the demodulate schceme for DSB-SC. >>> >>> I get the tx x PLL = 'c'. Pass this point 'c' through comb resonator, >find >>> gain and get my message signal. THIS IS WHERE I AM CONFUSED. WHAT >HAVENT I >>> CONSIDERED FOR THIS DEMOD SCHEME?? >>> >>> PLEASE HELP!!! >> >>Du da math instead of assuming de ansa. >> >>Jerry >>-- >>Engineering is the art of making what you want from things you can get. >>����������������������������������������������������������������������� >> > >OK, I done the hand analysis and found out that i didnt consider thephase>difference. Created a new demod scheme for SSB-SC. > >1. tx x PLL = 'a' > >2. 'a' x combresonator 1 = 'b' > >3. 'a' x ( -180 degree phase shift x combresonator 2) = 'c' %thereasoning>behind the -180 phase shift was the during modulation, the messagesignal>was phase shifted 90 degrees and the ocsillator was phase shifted 90 >degree as well. > >4. 'b' + 'c' = 'd' %add the two streams of signal > >5. 'd' x gain = (message signal acquired) > >Thx for kind and not so kind comments. Would love to hear your thoughtson>this demod scheme. >I tried implementing my above scheme with that -180 degree difference and then i realized that adding 'b' + 'c' = 'd' - cancels the two streams. (Well nuthing appears as my output so i guess that wat happened.) I am getting desperate, and m out of ideas. PLEASE HELP.

Reply by ●November 14, 20062006-11-14

10023101 wrote: ...> I tried implementing my above scheme with that -180 degree difference and > then i realized that adding 'b' + 'c' = 'd' - cancels the two streams. > (Well nuthing appears as my output so i guess that wat happened.) > > I am getting desperate, and m out of ideas. PLEASE HELP.I really don't know what you're trying to accomplish. Are you trying to invent a new demodulator? I can see that you're confused when you say that shifting the carrier and the modulation 90 degrees each amounts to 180 degrees total. It just doesn't work that way. I don't know what the comb filter is for, but there's a lot I don't know. Have you read up on any SSSB demodulation scheme? There's some good stuff at an elementary level in the ARRL handbook. A phasing modulator is easy to understand. Balanced modulators produce both sidebands of an AM signal, but not the carrier. Such a signal is practically useless in itself, but it's a useful building block. If either the modulating signal or carrier phase is changed, the phases of the sidebands will change too. It turns out that if both modulating signal and carrier are shifted 90 degrees, th phase of one of the sidebands will be the same as before and the other will be shifted 180 degrees. (Which one stays the same depends on the directions of the quadrature shifts.) When you do it shifted and unshifted in parallel paths and add the results, one of the sidebands is canceled out. A filter SSB modulator is conceptually even simpler, but not simpler to build. Simply pass the double-sideband filter through a filter that passes one of the sidebands and removes the other. To demodulate, reverse either process. The block diagram of a demodulator might not look like it's doing that, but analysis shows that it is. You demodulate by beating the signal to baseband and either removing the image with a filter (filter method) or by not generating it in the first place (phasing method). Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������

Reply by ●November 14, 20062006-11-14

Jerry Avins wrote:> 10023101 wrote: > >> hey guys, just wanted to know if any1 could please shred sum light on wat >> would the differnce in demodulation schemes of double side band >> suppressed >> carrier and single side band suppressed carrier. This is what i done with >> matlab coding for modulation and demodulation. >> 1. DSB-SC: >> - Modulation: (message signal 500hz) multiply by (carrier frequency >> 7000hz) ie: cos (2 pi 500 t) x cos (2pi7000t) = tx (transmission signal) > > > Wot makes u tink dats suppressed carrier? It's straight AM. >Straight AM would be cos(2 pi 500 t) x (1 + cos(2 pi 7000 t)). His expression is, indeed, for DSB-SC. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Posting from Google? See http://cfaj.freeshell.org/google/ "Applied Control Theory for Embedded Systems" came out in April. See details at http://www.wescottdesign.com/actfes/actfes.html

Reply by ●November 15, 20062006-11-15

Tim Wescott wrote:> Jerry Avins wrote: > >> 10023101 wrote: >> >>> hey guys, just wanted to know if any1 could please shred sum light on >>> wat >>> would the differnce in demodulation schemes of double side band >>> suppressed >>> carrier and single side band suppressed carrier. This is what i done >>> with >>> matlab coding for modulation and demodulation. >>> 1. DSB-SC: - Modulation: (message signal 500hz) multiply by (carrier >>> frequency >>> 7000hz) ie: cos (2 pi 500 t) x cos (2pi7000t) = tx (transmission signal) >> >> >> Wot makes u tink dats suppressed carrier? It's straight AM. >> > Straight AM would be cos(2 pi 500 t) x (1 + cos(2 pi 7000 t)). His > expression is, indeed, for DSB-SC.Right. jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������