Problem 4: A DSB-SC signal is modulated by the signal m(t)=2cos 2000πt + cos 6000πt the carrier signal is c(t) = 100 cos 257fct. fc = 1 MHz where The modulated signal is u(t) = m (t)<(t) Determine and sketch the spectrum of the AM signal ⑤ Determine the average power in the frequency components.

An FM signal has a maximum frequency deviation of 1500h and a modulating frequency of 500h, its total power is 6500w, applied to a resistive load of 1ohm, the carrier frequency is 400Mhz. Determine the sensitivity of the modulator, and the magnitude spectrum

1) Find the energy in the signal x[n] = 2(0.12)", n20. %3D 2) Given a periodic signal of x[n] = 2cos(2 m/4) whose period is N = 4. Find its average value and signal power. 3) Given a periodic signal of x[n] = 9e24 whose period is N=4. Find its signal power. 4) Sketch each signal and its even and odd parts. (1) x[n] = 8(0.5)' u[n] (ii) x[n]= u[n] (iii) x[n]=1+ u[n] (iv) x[n] = u[n]-u[n – 4] (v) (vi) x[n]= {6,4,2, 2}

Measurements taken of a square-wave signal using a frequency-selective voltmeter (called a spectrum analyzer) show its spectrum to contain adjacent components (spectral lines) at 98 kHz  and 126 kHz of amplitudes 63 mV and 49 mV, respectively. What would direct measurement of the fundamental show its frequency and amplitude to be? What is the rms value of the fundamental? What are peak-to-peak amplitude and period of the originating square wave?

Question 4. Select the statement that best describes the PM wave.a. Carrier phase angle changes represent the PM modulated signal, however, unlike FM and AM modulatedcarriers, it is not always easy to see these phase changes in the plot.b. The FM signal accurately represents the message.c. Although PM and FM techniques are classified as angular modulation techniques, they cannot be usedinterchangeably (i.e., modulated with FM and demodulated with PM, and visa versa).d. All statements are correct.

A spectrum analyzer with an input impedance of 200 is used to measure the power spectrum of an AM signal at the output of a preamplifier circuit. The AM signal has been modulated with a sine wave. The effective carrier power, Pc, is 750mw, and each sideband, PusB and PLSB, is 120mW. Compute the following: 1- The total effective power Pr. 2- The peak carrier voltage, Vc- 3- The modulation index, m, and the percent modulation index. 4- The modulation voltage,Vm. 5- The lower -and upper - sideband voltages, VLSB and VUB. 6- Sketch the waveform that you would you see with an oscilloscope if it were placed in parallel with the spectrum analyzer.

A SSB AM signal is generated by modulating an 8 kHz carrier by the signal m(t) = cos 2000πt. The amplitude of the carrier is Ac = 10. 1. Determine the (time domain) expression for the lower sideband of the SSB AM signal. 2. Determine the magnitude spectrum of the lower sideband SSB signal. 3. Determine the (time domain) expression for the upper sideband of the SSB AM signal. 4. Determine the magnitude spectrum of the upper sideband SSB signal. 5. Find the power of the modulated signal. Hint: Fourier Transform of sin (27 fot) is 8(f+fo)-(f-fo) and Fourier Transform of cos (27 fot) is 8(ƒ + fo) +18(ƒ - fo).

7) Calculate Log2(64) 64,32,6, and 2 9) What is the bandwidth of a signal that ranges from 5 MHz to 10 MHz? 10MHz. 5MHz. 5KHz. 10KHz.

Q 2 : An audio signal given by 15 sin( 000 pi t)+20 sin(8000 pi t) amplitude modulated DSB-FC) a sinusoidal carrier wave 60 sin(100,000 ) a. Derive an expression for the modulated signal. b. Find the modulation index. c. Find the spectrum of the modulated signal. d. Sketch the spectrum of the modulated signal e. Which type of demodulation method you propose to reconstruct the audio at receiver. Why? Q 2 : A modulating signal is used to modulate a carrier signal(AM modulation). Let P T . P c ,P SB . P USB , P LSB and u are the total power, carrier power, side band power, upper side band power, lower side band power and modulation index respectively, Prove the following: a. P c =P T ( 2 2+m^ 2 ) b. P SB =P T ( m^ 2 2+m^ 2 ) c. P USB =P LSB = 1 2 ( m^ 2 2+m^ 2 )P T

3.7 A modulating signal is of the form: m(t) = 5 sin (2000nt) and the carrier signal c(t) = 10 sin (20000rt) 1. Determine the modulation index. 2. Find the percentage of modulation. 3. Find the frequencies of the sideband. 4. Find the amplitude of each the side bands. 5. What will be the bandwidth of the modulated signal?