hi help in these questions!

[vjfaisal]

hi!!
im sorry for not giving the choices in this question, now here it. but i have aconfusion in Q#2 also ,
so if anyone know please anwer it and mention how u do it.

Q#1
for tone modulation (AM/DSB with carrier) the power effeicency is ??

a) increases monotonically with modulation index

b) decreases monotonically wih modulation index

c) in indepandent of modulation index

d) is a constant


Q#2:-
carrier frequency of modulated signal m(t) cos50000t can be changed to 40k rad/sec .by applying down conversion by multiplying it with signal of frequency (rad/sec)

A) 90k

B) 40k
C 10k

D) both A and B


best regards

 

[some1mohsin]

Q #1 = option C
and
Question # 2= Option A

 

[vjfaisal]

hi some 1 mohsin ,

pplease tell me how u solve these question ,about there basics or ant formula
please.




best regards

 

[rickleicn]

hi help in these questions!!!!!!!!!!!!!!!!!!!1

for question 2,my answer is Option C.

 

[samasimo]

Q#1

correct answer is (A)
as m increases , eff increases.
However, in practical situations m≤1 so eff≤33% . Theriotically, m can take any value and eff will increase as m increases

Q#2

(A) and (C) are correct answers. i think u mistyped option D or u exchanged B & C!!!!!!

 

[amriths04]

q2)
50k-10k=40k
and 90k-50k=40k

therefore both are right. and they are like images of each other.

regards,

hi!!
im sorry for not giving the choices in this question, now here it. but i have aconfusion in Q#2 also ,
so if anyone know please anwer it and mention how u do it.

Q#1
for tone modulation (AM/DSB with carrier) the power effeicency is ??

a) increases monotonically with modulation index

b) decreases monotonically wih modulation index

c) in indepandent of modulation index

d) is a constant


Q#2:-
carrier frequency of modulated signal m(t) cos50000t can be changed to 40k rad/sec .by applying down conversion by multiplying it with signal of frequency (rad/sec)

A) 90k

B) 40k
C 10k

D) both A and B


best regards

 

[correlator2006]

Q1)i think power efficiency is the contribution of audio signal power in over all AM DSB power

EFFICIENCY=Paudio/(Pcarrier+Paudio)
i think that the correct answer is A.
Example:
for transmission of single tone modulated signal s=Ac(1+mcos(Wmt))cosWct
Ps=Ac^2/2+(mA)^2/4
Paudio=(mAc)^2/4
Efficiency=m^2/(m^2+2)
Efficiency increases if m increases


Q(2)

TO MAKE DOWN CONVERTER I THINK THAT THE BEST ANSWER are A or C

to make down conversion ,we simply multiply signal with sinsoidal signal with freq 90rad/sec

s(t)cos 50000t * cos90000t=s(t)/2[cos(90000-50000)t+cos(900000+500000)t]"revise trigeometric propertse"
=s(t)/2[cos(40000)t+cos(140k)t]
using low pass filter we can remove the high freq component
and so we obtain s(t)/2[cos(40000)t]

by the same way u can use 10 Krad sinsoidal instead of 90K rad/s
A and C are the best

Hopfully i help you
Mostafa

 

[samasimo]

A) 90k

B) 40k
C 10k

D) both A and B

by the same way u can use 10 Krad sinsoidal instead of 90K rad/s
D is teh best

How come??
Option D says A and B (90& 40) NOT 90& 10

Thats why i told him

(A) and (C) are correct answers. i think u mistyped option D or u exchanged B & C!!!!!!

unfortunately, the man doesnt follow or track the answsers to his questions :!::!:

 

[rickleicn]

hi help in these questions!!!!!!!!!!!!!!!!!!!1

yes,the topic poster should be serious to his questions, please try to get the principles not only answers.

 

[shetoos_asu_65]

I AM SURE FROM THE FOLLOWING...asking experts:

1) Q1: a is the correct answer
2) Q2: a,c are correct

that is all
bye