Telcommunication laboratory ybu engineering solution homework quizz exam (15)

YILDIRIM BEYAZIT UNIVERSITY EE 305 – TELECOMMUNICATIONS 1 PRELIMINARY MANUAL – 2 – DSB and SSB Modulation & Demodulation Preliminary work: 1) Two signals m1(t) and m2(t),amplitude of 2Vp-p, both band limited to 5000 rad/s are to be transmitted simultaneously over a channel by the multiplexing scheme shown in Figure . The signal at point b is the multiplexed signal, which now modulates a carrier of frequency 20000 rad/sn. The modulated signal at point c is transmitted over a channel. a-) Sketch signal spectra at points a, b and c. b-) Design a receiver to recover signal m1(t) and m2(t) from the modulated signal at point c.

Figure

2) A SSB signal is generated by modulating a fc carrier by the signal m(t) = cos 2000π.t The amplitude of the carrier is Ac. (a) Determine the hilbert transform of m(t). (b) Determine the time domain expression for the Lower Sideband of the SSB signal. (c) Determine the magnitude spectrum of the Lower Sideband SSB signal. (d) Calculate the power of the SSB signal. (e) Bandwidth = ?

3) A wiring diagram of TETRA-BB hardware blocks to generate a SSB signal is given in Figure 1.

Figure 1: Wiring of TETRA-BB hardware blocks to generate a SSB signal a-) Draw the time domain expression of the output signal of function generator module tuned to 1 kHz for message signal. It provides an sinusoidal output signal with a peak to peak amplitude of 4V (for a time range of 0- 3 ms). b-) Draw the time domain expression of the output signal of a master signals module tuned to give a cosine wave of 50 kHz for carrier signal and a peak to peak amplitude of 4V (for a time range of 0 – 1 ms). c-) Draw the time domain expression of the input and output signal of a Phase Shifter module (for a time range of 0 – 3 ms). Adjust the phase shifter for 90 degree !!!

What is the aim of usage of phase shifter? Prove this. d-) Calculate the mathematical expressions and Draw the approximate time domain graphics for each of the following steps, according to connections in Figure 1. Use the master(tone) signal and the carrier signal respectively in question 3-a, question 3-b:   

Output of the first Multiplier module (for a time range of 0 – 3 ms).

Output of the second Multiplier module (for a time range of 0 – 3 ms).

Output of the Adder module (for a time range of 0 – 3 ms). Assume that gain parameters g and G set to 1.

e-) Sketch the spectrum of the signal obtained at output of the adder module.

A wiring diagram of TETRA-BB hardware blocks to demodulate a SSB signal is given in Figure 2.

Figure 2 : Wiring of TETRA-BB hardware blocks to demodulate a SSB signal. f-) Calculate the mathematical expressions and sketch the spectrum of the signals obtained output of the multiplier module which is used at demodulator part. g-) Determine the cutoff frequency of Tunable LPF to recover message signal.

Draw the approximate both spectrum and time domain graphic of the output of a Tunable LPF module when we connect output of third multiplier module (for a time range of 0 – 3 ms).