yousef_ob Posted October 16, 2005 Report Share Posted October 16, 2005 hello, plz could anyone solve this for me:in a DSB modulation if we assume that the modulating signal is a power signal, why this integration is zero, plz i want the mathemetical prove for the attached equationthanx very much Quote Link to comment Share on other sites More sharing options...
yousef_ob Posted October 16, 2005 Author Report Share Posted October 16, 2005 sure m(t) is the modualting power signal Quote Link to comment Share on other sites More sharing options...
yousef_ob Posted October 19, 2005 Author Report Share Posted October 19, 2005 C'mon i have asked a question it wasnt a joke or a story. plz is there anyone could solve that for me??!! ??? Quote Link to comment Share on other sites More sharing options...
Guest Yevgenip Posted October 20, 2005 Report Share Posted October 20, 2005 Can you explain what are the parameters and what are the functions? The equation is not very clear. Quote Link to comment Share on other sites More sharing options...
yousef_ob Posted October 21, 2005 Author Report Share Posted October 21, 2005 hello,in the attached equation m(t) is a power signal - not an energy signal. we know that DSB modulation is defined by the equation m(t) cos (2*pi * fc*t). so that the power of this signal is the integration of the sequared equation over the period - i.e power = integration over period of (m(t) cos(2*pi* fc*t)^2. we know that cos^2(wc*t)= .5(1+ cos(2*wc*t))then multiply this by m^2(t) and integrate over the period, then the first term in 0.5 * the power of the mudulating signal (m(t)). and the second term is zero i am asking why it is zero. i gonna attatch the equation again Quote Link to comment Share on other sites More sharing options...
yousef_ob Posted October 30, 2005 Author Report Share Posted October 30, 2005 Hello,I thought that i give u the time to think in my quwstion. but to this moment i didnt get a solution to this problem.i hope someone will help me.bye Quote Link to comment Share on other sites More sharing options...
audioguru Posted October 30, 2005 Report Share Posted October 30, 2005 Hi Yousef,I haven't looked at math like that for about 40 years but I'll try answering your question.It looks like it is calculating average suppressed-carrier (?) DSB AM modulated power. I think the 2nd part of the equasion is zero because it is the minimum power and the 1st part is the peak power. ;D Quote Link to comment Share on other sites More sharing options...
yousef_ob Posted October 31, 2005 Author Report Share Posted October 31, 2005 thanx a lot. nice try!!i need a mathemetical solution. Quote Link to comment Share on other sites More sharing options...
ECET0purdue Posted November 1, 2005 Report Share Posted November 1, 2005 been awhile for me too but dont you have to change the cos to sin when you do integration. thus you would get 0. Quote Link to comment Share on other sites More sharing options...
yousef_ob Posted November 2, 2005 Author Report Share Posted November 2, 2005 i think that you didnt noticed that the cos is multiplied by another time variable function so you cant integrate that simple. anyway thanx abt ur try Quote Link to comment Share on other sites More sharing options...
yousef_ob Posted November 6, 2005 Author Report Share Posted November 6, 2005 thanx i solved it Quote Link to comment Share on other sites More sharing options...
prateeksikka Posted November 12, 2005 Report Share Posted November 12, 2005 even if u omit the signal integral of cosine wave i.e cos(2*w*t) over one period of T is zero.thats why it is zero! ;D Quote Link to comment Share on other sites More sharing options...
yousef_ob Posted November 15, 2005 Author Report Share Posted November 15, 2005 hello,fom the maths point of view this is forbidden because m(t) as shown is a function of time not a constantbye ;D Quote Link to comment Share on other sites More sharing options...
prateeksikka Posted November 16, 2005 Report Share Posted November 16, 2005 hi yousef!i didnt understand what did u say!why cant we integrate a time function?i guess theres no problem in it. Quote Link to comment Share on other sites More sharing options...
ECET0purdue Posted November 17, 2005 Report Share Posted November 17, 2005 ummmm back to the math point of view....if i recall right was that not the if 1 person can build a house in 3weeks then 3000 people can build it in 3 secs....dam math.. Quote Link to comment Share on other sites More sharing options...
prateeksikka Posted November 18, 2005 Report Share Posted November 18, 2005 i guess i cited same example for audioguru when we were discussing the difference between science (physics) and maths more preciselyscientist and engineer,scientist says its possible to build while engineers say NO! ;D Quote Link to comment Share on other sites More sharing options...
audioguru Posted November 18, 2005 Report Share Posted November 18, 2005 There aren't any scientist animals around anymore. They were replaced by marketing folks who know nothing about anything. ;D Quote Link to comment Share on other sites More sharing options...
prateeksikka Posted November 19, 2005 Report Share Posted November 19, 2005 Strange boss!ultimately its the market to the end user!So strange of you.audioguru!could u please post an answer for my query in Circuits/general requests/Frequency selectionplease!thanks! Quote Link to comment Share on other sites More sharing options...
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