Mumbai University > Computer Engineering > Sem 3 > Electronic Circuits and Communication Fundamentals

Marks: 10 Marks

Year: May 2015

Q=100

Intermediate frequency=$f_i=455 kHz$

Image frequencies and rejection at 1 MHz

$f_s=1MHz$

Image frequency $=f_{si}=f_s+2f_i$

$f_{si} =1 MHz +2(455 kHz)=1.91 MHz \\ ρ =\dfrac{f_{si}}{f_s} -\dfrac{f_s}{f_{si}} =\dfrac{1.91}{1}-\dfrac{1}{1.91}=1.39$

Image frequency rejection ratio is given as

$α=\sqrt{1+Q^2 ρ^2 }=\sqrt{1+100^2 1.39^2}=139 \\ α \ \ in \ \ dB= 20 \log_{10} 139=42.86 dB$