# HELP! STUDENT IN NEED!!!!!-----------------------------HELP!

Status
Not open for further replies.

#### quinner

##### New Member
Hello everybody. I am a first year student in Dublin Ireland. I am doing a communications technology subject that i am not very good at. Could sombody please give me the solutions to the problems below;

Question 1
Assume the following polynomial is the generator for a cyclic code and design a syndrome testing circuit using shift registers.
G(X) = 1 + X + X4 + X6

Question 2
The generator polynomial of a (15,11) Hamming code is defined as
g(X) = 1 + X + X4

(i) Design a feedback register encoder implementing this coding scheme.
(ii) Illustrate the encoding procedure with the message 11001101011, by listing the successive states of the registers.

Question 3
Consider a systematic block code that forms it’s codewords by adding to the bits mi of the messages, the parity bits pi defined by the following equations:

p1 =m1 +m2 +m4
p2 =m1 +m3 +m4
p3 =m1 +m2 +m3
p4 =m2 +m3 +m4

a) Find the generator matrix and the parity check matrix for the code.
b) How many errors can the codeword correct?
c) Is 10101010 a valid codeword?
d) Is 01011100 a valid codeword?

Question 4
The maximum and minimum values taken by the envelope of an AM signal are 3.5 and 0.5 Volts. What is the modulation index? The radio transmitter radiates 10kW. How much is the carrier power?

Question 5
An angle-modulated wave is described as:
V(t) = 10cos(2p(10^8)t + sin(3142t))
Determine:
a) The modulation index
b) The frequency deviation
c) The frequency components of the spectrum using Bessel function tables

Thank you very much for taking the time to read this, and for any help.

#### Edmond

##### Member
Question 4
The maximum and minimum values taken by the envelope of an AM signal are 3.5 and 0.5 Volts. What is the modulation index? The radio transmitter radiates 10kW. How much is the carrier power?

The carrier is 3.5V (without modulation, then m=0%). The voltage change is 3.5V-0.5V=3V. m=(3)/(3.5)*100%=85,71%. The power of the carrier can’t be calculated, because it depends on the modulation frequency (and of course the modulation signal type). The modulation signal is Um=Up*sin(wt) ?

Question 5
An angle-modulated wave is described as:
V(t) = 10cos(2p(10^(wt) + sin(3142t))
Determine:
a) The modulation index
b) The frequency deviation
c) The frequency components of the spectrum using Bessel function tables (the good answer)

#### quinner

##### New Member
Huh? I'm a little slow, so i don't get it. by the way, the smily face is the number 8, dunno why that happened

#### Russlk

##### New Member
I am glad that I am not attending your class. I don't even want to know the answers.

#### quinner

##### New Member
I'm still at them, i'm not really looking for answers, just solutions, i'd really prefer to understand what's being asked.

#### FRIED

##### New Member
Q4: The average = carrier level = (3.5+.5)/2 = 2, Modulation percentage
= ((3.5-2)/2)*100 = 75%. Sideband voltage relative to carrier (each sideband) = .75/2 = .375. Since power is proportional to V², relative power in each sideband is .375² = .1406. The total relative power is
carrier plus two sidebands = 1+.14+.14 = 1.28. The carrier power of the 10KW transmission is 10,000/1.28 = ~7.8KW

Status
Not open for further replies. 