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JEE Main 201911 JanuaryMorning Shift
Exam
JEE Main
Year
2019
Date
11 January
Shift
Morning Shift
Subject
Physics
Chapter
Communication System

JEE Main 2019 · 11 January · Morning Shift · Physics · Communication System

An amplitude modulated signal is given by V(t)=10[1+0.3 . (2.2 ×...

An amplitude modulated signal is given by V(t)=10[1+0.3cos⁡(2.2×104t)]sin⁡(5.5×105t).\mathrm{V}(\mathrm{t})=10[1+0.3 \left.\cos \left(2.2 \times 10^{4} \mathrm{t}\right)\right] \sin \left(5.5 \times 10^{5} \mathrm{t}\right) . Here t\mathrm{t} is in seconds. The sideband frequencies (in kHz\mathrm{kHz} ) are, [Given π=22/7\pi=22 / 7 ]An amplitude modulated signal is given by V(t)=10[1+0.3 . (2.2 × 10^ 4 t)] (5.5 × 10^ 5 t) . Here t is in seconds. The

Options

  1. A1785 and 1715
  2. B178.5178.5 and 171.5171.5
  3. C89.2589.25 and 85.7585.75
  4. D892.5892.5 and 857.5857.5

Correct answer

C. 89.2589.25 and 85.7585.75

Step-by-step solution

Equation given
<br><br>\begin{array}{l}
\mathrm{V}(\mathrm{t})=10\left[1+0.3 \cos \left(2.2 \times 10^{4}\right)\right] \\
\sin \left(5.5 \times 10^{5} \mathrm{t}\right) \\
=10+1.5\left[\sin \left(57.2 \times 10^{4} \mathrm{t}\right)+\sin \left(52.8 \times 10^{4} \mathrm{t}\right)\right] \\
\omega_{\mathrm{c}}+\omega_{\mathrm{w}}=57.2 \times 10^{4}=2 \pi \mathrm{f}_{1}
\end{array}<br><br>
<br>f1=57.2×1042×(227)=9.1×104≃91KHz<br><br>\mathrm{f}_{1}=\frac{57.2 \times 10^{4}}{2 \times\left(\frac{22}{7}\right)}=9.1 \times 10^{4} \simeq 91 \mathrm{KHz}<br>
<br>ωc−ωw=52.8×104<br><br>\omega_{\mathrm{c}}-\omega_{\mathrm{w}}=52.8 \times 10^{4}<br>
<br>f2=52.8×1042×(227)≃84KHz<br><br>\mathrm{f}_{2}=\frac{52.8 \times 10^{4}}{2 \times\left(\frac{22}{7}\right)} \simeq 84 \mathrm{KHz}<br>
An amplitude modulated signal is given by V(t)=10[1+0.3 . (2.2 × 10^ 4 t)] (5.5 × 10^ 5 t) . Here t is in seconds. The
Upper side band frequency (f1)\left(f_{1}\right) is
<br>f1=fc−fw=52.8×1042π≈85.00kHz<br><br>\mathrm{f}_{1}=\mathrm{f}_{\mathrm{c}}-\mathrm{f}_{\mathrm{w}}=\frac{52.8 \times 10^{4}}{2 \pi} \approx 85.00 \mathrm{kHz}<br>
Lower side band frequency (f2)\left(\mathrm{f}_{2}\right) is
<br>f2=fc+fw=57.2×1042π≈90.00kHz<br><br>\mathrm{f}_{2}=\mathrm{f}_{\mathrm{c}}+\mathrm{f}_{\mathrm{w}}=\frac{57.2 \times 10^{4}}{2 \pi} \approx 90.00 \mathrm{kHz}<br>
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