**Unformatted text preview: **EE 3 1200 / R Communication Theory
Midterm 1 1\
Name :\
Shihan
Re-za
1 . D . # ( last four digits ) :\
45 64
Note : ( 1 ) Close book; ( 2 ) No electronic device : ( 3 ) Time : 3: 30- 4: 45 pm; Date: 11/ 4/ 2014: Room: Harris 9\
1 . Consider a DSB - SC signal with noise passes through a demodulator for SSB- SC signals.
V , ( 1 )
1 1 ( 1 )
V 2 ( 1 )
CAH
( X )
HBCD )
Vo ( 7)
V . ( 1 )
The input signal plus noise is v , ( 7 ) = s , ( 1 ) + n , ( 1 ) where s, ( 1 ) = Am ( 7 ) cos Z *` f. I. M ( 1 ) = cos Z * f; I is the message signal
with In < IN , carrier frequency is $ 2 {~ , and noise ~ , ( 1 ) has power spectral density function G, (f ) = 17 . The local
carrier is v ( 7 ) = 2 cos 2 * * f t . The carrier filter is H ( F ) = 4 for- f. - I'M S FS- f, and F. < < < f + FM , and HI ( S ) = 0
otherwise . The low pass filter is H & (F ) = O for I f Is. fir , and HI, (F ) = 0 otherwise .
( 2 ) ( 5% ) Draw H ( f ) and H * ( f ) .
( 6 ) ( 10%) Determine the signals s, ( 1 ) , $2 ( 1) , and s, ( 1) at v , ( 1 ) , 1 2 ( 1) , and v.( 1 ), respectively .\
( C ) ( 10% ) Draw power spectral density functions for noises ni ( 1 ) , 12 ( 1), and n, (1 ) at vi ( 7 ) , V 2 ( 1), and V, ( 7), respectively.
( d ) ( 15% ) Determine input SNR , output SNR , and figure of merit .\
9 ) H ( -$ ) = 4 - fc- firstE- fic`
A H ( S )
41
- fe - fm . - FC
J C
frafa_ f + 5
HB(S )
f <
- I've
- m
b )
` ( - 1 ) = S* ( + ) + ni(t )`
Si ( + ) = Am ( 1 )` cogan fet
m ( 4 ) = cos 2 17 Smith
+$
Si ( + ) = Acosentm + cos ZA fet
8 : * 5 m
Si ( + ) [ 2 A COSATT ( Scuffm) t,
3, A `s 2 7 (8 + fm) t
$ 2 ( 4 ) = 2 Am ( f ) + 2 A COSE# ( 2 Sctfi'm)`
`thin! !) sos an ```
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- Signal Processing, Low-pass filter, Shihan