please tell how to solve this

[vjfaisal]

hi
please help me in this solving this question or kindly tell me the procedure or any formula to easy solve it.


Q:- In AM modulation has the output

y(t)=[A +m(t)]cos(2100t)=[A +Bsin(200t)]*cos(2100t)
the carrier power is 12.5 w, and power efficiency is 27%

claculate values of A,B,and modulation index(m).

best regards

 

[ahmed_nasr]

please tell how to solve this!!!!!!!!!!!!!

A=Ec=carrier amplitude

B=Em=intelligence amplitude

carrier power = (Ec^2)/2=12.5 --> Ec=A=5


there was a mistake here , see my second post for the rest of the solution

 

[amriths04]

Re: please tell how to solve this!!!!!!!!!!!!!

hi ahmed,
is not efficiency= intelligence power/total power
??

A=Ec=carrier amplitude

B=Em=intelligence amplitude

carrier power = (Ec^2)/2=12.5 --> Ec=A=5

efficiency = intelligence power/carrier power

we have Ptotal=Pc(1+(m^2)/2)

Pintelligence=Ptotal-Pc=Pc*(m^2)/2

therefore , efficiency=(m^2)/2 --> m=0.73

m=Em/Ec =B/A --> B=3.674

 

[ahmed_nasr]

Re: please tell how to solve this!!!!!!!!!!!!!

hi ahmed,
is not efficiency= intelligence power/total power
??

A=Ec=carrier amplitude

B=Em=intelligence amplitude

carrier power = (Ec^2)/2=12.5 --> Ec=A=5

efficiency = intelligence power/carrier power

we have Ptotal=Pc(1+(m^2)/2)

Pintelligence=Ptotal-Pc=Pc*(m^2)/2

therefore , efficiency=(m^2)/2 --> m=0.73

m=Em/Ec =B/A --> B=3.674

yes u r right ..... i am sorry for that mistake

efficiency = intelligence power/total power
=((m^2)/2)/(1+(m^2)/2)=0.27--> m=0.86

m=Em/Ec =B/A --> B=4.3

 

[vjfaisal]

Re: please tell how to solve this!!!!!!!!!!!!!

hi
it is requested to mr ahmes_nasr and amriths04 to kindly give me ur e-mail addresses. if u donot mind it.

and kindly give the idea how to solve above last question.




best regards

 

[amriths04]

Re: please tell how to solve this!!!!!!!!!!!!!

hi vjfaisal, you can pm me in here any time.

regards,

hi
it is requested to mr ahmes_nasr and amriths04 to kindly give me ur e-mail addresses. if u donot mind it.

and kindly give the idea how to solve above last question.




best regards