(Solved): LABORATORY 3: DIGITAL MODULATION 1.0 Objective To analyse the characteristic of Amplitude Shift Keyi ...

LABORATORY 3: DIGITAL MODULATION 1.0 Objective To analyse the characteristic of Amplitude Shift Keying (ASK), Frequency Shift Keying (FSK) and Phase Shift Keying (PSK). To plot Amplitude Shift keying (ASK), Frequency Shift Keying (FSK) and Phase Shift Keying (PSK) using Scilab. 2.0 Theory Amplitude Shift Keying (ASK) is the digital modulation technique. In amplitude shift keying, the amplitude of the carrier signal is varied to create signal elements. Both frequency and phase remain constant while the amplitude changes. In ASK, the amplitude of the carrier assumes one of the two amplitudes dependent on the logic states of the input bit stream. This modulated signal can be expressed as:

Amplitude shift keying (ASK) in the context of digital signal communications is a modulation process, which imparts to a sinusoid two or more discrete amplitude levels. These are related to the number of levels adopted by the digital message. For a binary message sequence there are two levels, one of which is typically zero. Thus the modulated waveform consists of bursts of a sinusoid. Figure 3.1 illustrates a binary ASK signal (lower), together with the binary sequence which initiated it (upper). Neither signal has been band limited. Figure 3.1 ASK modulated output wave Frequency Shift Keying refers to a type of frequency modulation that assigns bit values to discrete frequency levels. FSK is divided into noncoherent and coherent forms. In noncoherent forms of FSK, the instantaneous frequency shifts between two discrete values termed the "mark" and "space" frequencies. In coherent forms of FSK, there is no phase discontinuity in the output signal. FSK modulation formats generate modulated waveforms that are strictly real values, and thus tend not to share common features with quadrature modulation schemes. Figure 3.2 FSK modulated output wave Phase Shift Keying in a digital transmission refers to a type of angle modulation in which the phase of the carrier is discretely varied-either in relation to a reference phase or to the phase of the immediately preceding signal element-to represent data being transmitted. For example, when encoding bits, the phase shift could be 0 degree for encoding a " 0 ," and 180 degrees for encoding a "1," or the phase shift could be - 90 degrees for " 0 " and +90 degrees for a "1," thus making the representations for " 0 " and "1" a total of 180 degrees apart. Some PSK systems are designed so that the carrier can assume only two different phase angles, each change of phase carries one bit of information, that is, the bit rate equals the modulation rate. If the number of recognizable phase angles is increased to four, then 2 bits of information can be encoded into each signal element; likewise, eight phase angles can encode 3 bits in each signal element. I Iyuit J.J ur on iluuulateu uutuut valive 3.0 Equipment & Software Computer Unit with Ms Windows or Linux operating system installed Scilab version 6.1 .0 4.0 Procedures Launch Scilab. Open SciNotes. Write a Scilab command to represent the Amplitude Shift Keying (ASK) signal with the given information: Binary signal [10101011] Sampling frequency

Source Code:msg = [10 10 10 1 1]; A_freq = 3; b_msg = [ ; ; ask_msg = [ ]; = 0:1/Fs:1-1/Fs; for cnt = 1:length(msg) if msg(cnt) == 0; b_msg = [b_msg zeros(1,Fs)]; ask_msg = [ask_msg 1.**) else b_msg = [b_msg ones(1,Fs)]; ask_msg = [ask_msg 2.* end end subplot(211); plot(b_msg);mtlb axis([0,length(b_msg),-1,2]) title('Binary Message'); subplot(212); plot(ask_msg); title('ASK Signal'); Save the program with filename .sce extension. Execute the program and observe the output or waveforms. Write a Scilab command to represent the Phase Shift Keying (PSK) signal with the given information: Binary signal

Sampling frequency

Source Code:msg = [10 1 0 1 0 1 1]; A_freq = 3; b_msg = [ ]; psk_msg = [ ]; = 0:1/Fs:1-1/Fs; for cnt = 1:length(msg) if msg(cnt) == 0; b_msg = [b_msg zeros(1,Fs)]; psk_msg = [psk_msg 1.* sin(2**%pit)]; else b_msg = [b_msg ones(1,Fs)]; psk_msg = [psk_msg 1.**) end end subolot(211); plot(b_msg);mtlb axis([0,length(b_msg),-1,2]) title('Binary Message'); subplot(212); plot(psk_msg); title('PSK Signal');Save the program with filename .sce extension. Execute the program and observe the output or waveforms.5.0 Exercise Consider a binary signal [10 11 1010 1] and the sampling frequency is 200 Hz . Write Scilab command to represent the Amplitude Shift Keying (ASK) signal. Attach the generated message signal and ASK signal in your report. Consider a binary signal [10110101] and the sampling frequency is 200 Hz . Write Scilab command to represent the Phase Shift Keying (PSK) signal. Attach the generated message signal and PSK signal in your report. In your lab discussion, c