03-11-2016, 03:20 PM
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Course Educational Objectives:
Conceptualize the importance of modulation its need, effects of Noise and interference on performance, and strategize the requirements along with the limitations and remedies for enhancing system performance.
Targeted Course Outcomes:
Categorize various modulation techniques used and select one most suitable for use in a typical wireless application and mobile standards and technologies in present, past and future sets and factors involved in doing so.
1. A sinusoidal carrier voltage of frequency 10 MHz and amplitude 200 volts is amplitude modulated by a sinusoidal voltage of frequency 10 KHz producing 40% modulation. Calculate the frequency and amplitude of upper and lower sidebands.
2. A tuned circuit of the oscillator in a simple AM transmitter uses a coil of 20 mili Henry with a capacitor of 50 micro Farads. If the oscillator output is modulated by audio frequencies up to 10 KHz what is the frequency range occupied by the modulator output?
3. A sinusoidal carrier voltage of amplitude 80 volts and frequency 800 KHz is amplitude modulated by a sinusoidal voltage of frequency 15 KHz resulting in minimum modulated carrier amplitude of 72 volts. Compute (a) the sideband frequencies (b) modulation index
4. A sinusoidal carrier voltage of frequency 1 MHz is amplitude modulated by sinusoidal wave of amplitude 75 volts with 80% modulation. Calculate (a) the unmodulated carrier amplitude (b) modulation index and © amplitude of each sideband
5. A sinusoidal voltage amplitude modulates another sinusoidal voltage of amplitude 2 KV to result in two sideband terms each of amplitude 200 volts. Compute the modulation index.
6. The rms value of an RF carrier voltage is 100 volts. After amplitude modulation by a sinusoidal audio voltage of 10 volts, the carrier component is suppressed (a) Compute the modulation index (b) Power of the resultant signal?
7. The rms value of an RF carrier voltage is 80 volts. Compute the rms value of the modulating voltage when it has been amplitude modulated to a depth of (a) 30 % (b) 50 %
8. Unmodulated RF carrier power of 2 KW sends a current of 5 amp rms through an antenna. On amplitude modulation by another sinusoidal voltage, the antenna current increases to 5.9 amps. Calculate (a) modulation index and (b) carrier power after modulation.
9. A broadcast transmitter radiates 1.08 KW when the modulation depth is 40 percent. Calculate the total power when the modulation index has been raised to 70 percent.
10. What is change in power efficiency if the carrier of a 80% modulated DSBFC is suppressed?
11. An AM modulator has output frequencies of 3, 3.5 and 4 KHz with unspecified voltage levels. If carrier power is 1 Kilo watts and efficiency is 35% then what are the voltage levels of the frequencies specified?