In spread spectrum communications, a pseudo-noise (PN) sequence converts _______ signal to ______ signal Select one option:   a. unmodulated, modulated b. narrowband, wideband c. none of other answers d. wideband, narrowband

q14-  Direct sequence spread spectrum (DSSS) system spreads the baseband signal by ________ the baseband pulses with a pseudo noise sequence Select one: a. Addition b. None c. Dividing d. Subtracting

In PM, as the frequency of the modulating signal decreases, the frequency deviation will ___________. a. increase b. be finite c. be constant d. decrease

Select an answer6. For an AM-DSB-SC system to become AM-DSB-TC, the modulating signal must include ...A. a CD offset.B. AC signals only.C. RF spectral components.D. only sine functions.

Question 3 a) For a single-frequency sine wave modulating signal of 3 kHz with a carrier frequency of 36 MHz, what is the spacing between sidebands? b) A carrier of 49 MHz is frequency-modulated by a 1.5-kHz square wave. The modulation index is 0.25. Sketch the spectrum of the resulting signal. (Assume only harmonics less than the sixth are passed by the system.)

A carrier signal is amplitude modulated by a sinewave. The resulting AM waveform is shown below. 3.5V- 1V- a) What is the amplitude of the carrier signal? b) c) To achieve 75 percent modulation, what amplitude of the modulating signal is needed? d) Calculate the effective voltage of the AM signal What is the modulation index?

Q7. Figure Q7(a) shows the spectrum of a frequency modulated waveform with a sinusoidal modulation. 12 4.8 5.0 5.2 5.4 5.6 5.8 6.0 Frequency/MHz Figure Q7: (a) Spectrum of a frequency modulated waveform with a sinusoidal modulation. (a) Is this modulated waveform described as narrowband or as wideband? (b) What is the value of the carrier frequency? (c) What is the value of the modulation frequency? (d) Determine the value of the peak frequency deviation. Plots of Bessel functions of the first kind are provided below in Figure Q7(b) to assist you. (e) Estimate the fraction of the total signal power at the carrier frequency. (f) Detection of such a frequency modulated signal is usually accomplished with the use of a discriminator. Describe the function of a discriminator. (g) What is the equivalent AM modulation index obtained if this signal in Figure Q7(a) is demodulated with a high-pass RC filter discriminator? J„(x) 1.0 0.8 0.6 0.4 0.2 -0.2 -0.4 Figure Q7: (b) Bessel functions of the…

4. Given FM modulator with the following parameters: Frequency deviation = 44 kHz Modulating signal, vm = 2 sin (2rókt) a) Determine the modulation index. b) Determine number of sets of significant side frequencies. c) Determine the bandwidth using both Bessel function and Carson's Rule. d) Sketch the output frequency spectrum for the Bessel approximation.

41. Noise is typically narrow spikes of voltage with high frequencies.Group of answer choices True False  42. SCA signal can be transmitted at 67-kHz subcarrier.Group of answer choices True False 43. In FM, as the modulating signal amplitude increases, carrier frequency also increases proportionately.Group of answer choices True False 44. The greater the amplitude of the modulating signal, the higher the frequency deviation rate.Group of answer choices True False 45. With no modulation, the carrier frequency will shift above or below its normal frequency.Group of answer choices True False 46. The higher the frequency of the modulating signal, the greater the frequency deviation of the carrier signal.Group of answer choices True False

Q6. Figure Q6 shows the line spectrum of a modulated signal (all components are positive and real). 3 1 232 234 236 238 frequency/kHz Figure Q6: Line spectrum of a modulated signal (a) Describe the modulation scheme. (b) What are the values of the carrier frequency, modulation frequency and the modulation index? (c) What is the transmission efficiency (ratio of modulated to total power) in this example? (d) The reception of this signal is undertaken with a superheterodyne detector using an intermediate frequency of 110 kHz. What is the appropriate local oscillator frequency? (e) Demodulation of this type of signal is usually accomplished using an envelope detector. Describe the principles of operation of an envelope detector and sketch an example circuit. (f) What considerations should be made about the component values in the design of an envelope detector in order to demodulate the signal after shifting to the intermediate frequency? Relative unitsS