EXPERIMENT: 3. PSK Modulation

AIM: To design and verify the characteristics of Phase shift keying Modulation and Demodulation.

APPARATUS REQUIRED: PC loaded with MULTISIM software.

SIMULATION PROCEDURE.• Open MULTISIM Software.• Click=> New => Design1• Click save as in Desk Top rename the Design1 to your circuit name.• Go to Component tool bar and select the components.• Draw the Schematic of Frequency shift keying modulator and demodulator as shown.• Specify the values of Amplitude and frequency for the same values of the input signals.• Set frequency of XFG1= 600 H / 12v, XFG2= 2 KHz/10v.• Design the comparator circuit using op-amp to restore the modulating signal.• Record the output waveforms.

RESULT: Thus the design of phase shift keying modulator and demodulator was completed and its output is verified.

EXPERIMENT: 2. FSK Modulation

AIM: To design and verify the characteristics of frequency shift keying modulation and demodulation.

APPA RATUS REQUIRED: PC loaded with MULTISIM software.

SIMULATION PROCEDURE.• Open MULTISIM Software.• Click=> New => Design1• Click save as in Desk Top rename the Design1 to your circuit name.• Go to Component tool bar and select the components.• Draw the schematic of frequency shift keying modulator and demodulator as shown.• XFG1 F=150 H, XFG2 F= 200 Hz, and XFG F =2KHz• Specify the value of amplitude and frequency for the same value below mentioned.• Click simulate button or press F5 key => RUN• Design the comparator circuit using op-amp to restore the modulating signal.• Record the waveforms.

RESULT:Thus the design of Frequency shift keying modulator and demodulator was completed and its output is verified by the frequency deviation and modulation index using simulation software.

EXPERIMENT: 1. ASK Modulation

AIM: To design and verify the characteristics of Amplitude Shift Keying Modulation and Demodulation using MULTISIM software.

APPARATUS REQUIRED: PC loaded with MULTISIM software

SIMULATION PROCEDURE.• Open MULTISIM Software.• Click=> New => Design1• Click save as in Desk Top rename the Design1 to your circuit name.• Go to Component tool bar and select the components.• Draw the schematic of Amplitude Shift Keying modulator as shown.• Specify the values of amplitude and frequency for the same to carrier and modulating signals.• XFG1: Square wave F=300H/V= 10, XFG2=SINE wave F=5 Khz/V=10.• Design the comparator circuit using op-amp to restore the modulating signal.• Record the output.

RESULTS:Thus design of amplitude shift keying modulator and demodulator was completed and its output is verified.

UNIVERSITY OF PANGASINAN – PENCOLLEGE OF ENGINEERING AND ARCHITECTURE

DEPARTMENT OF ELECTRONICS AND ELECTRICAL ENGINEERING

EXPERIMENT NO._1_ASK MODULATION

SUBMITTED BY:

Benavidez, GiovanniJuguilon, JasonManzon, Alvin

SUBMITTED TO:ENGR. JEFFREY P. BERIDA, ECE, ECT

SCORE:

DECEMBER 19, 2014

DIGITAL COMMUNICATIONS10:30-12:00 MTWTH

GROUP NG GWAPO

SCORE:

DECEMBER 19, 2014

DIGITAL COMMUNICATIONS10:30-12:00 MTWTH

GROUP NG GWAPO

Observation:

In this experiment, we tried to see how ASK (Amplitude Shift Keying Works). As pertaining to Digital Communication during our regular class, it is also called OOK (On and OFF Keying) and is the most seldom used Digital Modulation since it is very prone to Noise. First step was to construct the circuit diagram given containing a list of devices which include resistors, a transistor, a couple of function generators, and an oscilloscope to display the output waveform of the modulated signal. We haven’t had any problems with the simulation since ASK as we have studied was the simplest of the 3 Digital Radio Modulations namely: ASK, FSK, and PSK. AS we ran the circuit, we saw that the carrier frequency of high value responds accordingly to the modulating signal which is a digital signal of relatively lower frequency. At lower logic level, the modulated signal as shown at the oscilloscope is straight and has no frequency at all but at higher logic level, the modulated signal is the same as that of the carrier signal. It seems that the label OOK makes sense since we saw on the oscilloscope that the modulated signal is like turning on and off through time.

Conclusion:

In this experiment, we conclude that ASK (Amplitude Shift Keying) is digital modulation scheme that conveys data by changing, or modulating the amplitude of a reference signal or the carrier wave in proportion to the information signal and it is the simplest of the 3 Digital Radio Modulations namely: ASK, FSK, and PSK.It is also known as OOK(On and Off Keying).Logic levels are represented by different amplitudes of signals. Usually, one amplitude is zero for logic digital logic zero while is logic 1 represented by the actual amplitudes of some carrier wave.

SCORE:

DECEMBER 19, 2014

DIGITAL COMMUNICATIONS10:30-12:00 MTWTH

GROUP NG GWAPO

UNIVERSITY OF PANGASINAN – PENCOLLEGE OF ENGINEERING AND ARCHITECTURE

DEPARTMENT OF ELECTRONICS AND ELECTRICAL ENGINEERING

EXPERIMENT NO._2_FSK MODULATION

SUBMITTED BY:

Benavidez, GiovanniJuguilon, JasonManzon, Alvin

SUBMITTED TO:ENGR. JEFFREY P. BERIDA, ECE, ECT

SCORE:

DECEMBER 19, 2014

DIGITAL COMMUNICATIONS10:30-12:00 MTWTH

GROUP NG GWAPO

SCORE:

DECEMBER 19, 2014

DIGITAL COMMUNICATIONS10:30-12:00 MTWTH

GROUP NG GWAPO

Observation:

In this experiment, we tried to see how is FSK (Frequency Shift Keying) constructed and how it works. During our classes, we learned that unlike ASK, FSK requires 2 carrier frequency and upon looking at the circuit diagram given, we saw that 3 function generators are present. We then concluded that 3 frequencies must be controlled namely: the modulating signal, the mark frequency (higher), and the space (frequency). After this, we directly constructed the diagram consisting of resistors, transistors, function generator, and an oscilloscope to view the modulated signal together with the other 3 signals present. The moment we ran the constructed circuit, we got disappointed since the modulated signal that we are expecting was not alike with what we have in mind. We tried changing certain values like the frequency of the modulating signal and even replacing the op-amp but nothing happened so we resorted to just finding a circuit diagram in the internet that would suffice the experiment’s mistake. Luckily, we did found one but the only difference with the original to this one is that our current diagram doesn’t have an op-amp. As we simulated the new diagram, it perfectly created the FSK modulated signal we have studied in class. The modulated signal’s feature looks like the ASK for some reason but the differences include (1) the presence of two carrier frequency and (2) at lower logic level, the modulated signal takes the form of the space frequency and at higher logic level, the modulated signal takes the mark frequency.

Conclusion:

In this experiment, we conclude that a Frequency-shift keying (FSK) is a frequency modulation scheme in which digital information is transmitted through discrete frequency changes of a carrier wave in proportion to the information signal and it is the oldest and simplest form of modulation used in modems. We then concluded that 3 frequencies must be controlled namely: the modulating signal, the mark frequency (higher or binary 1), and the space (frequency or binary 0).Phase discontinuities did not occur in this experiment since it is a smooth transitions at zero crossing.

SCORE:

DECEMBER 19, 2014

DIGITAL COMMUNICATIONS10:30-12:00 MTWTH

GROUP NG GWAPO

UNIVERSITY OF PANGASINAN – PENCOLLEGE OF ENGINEERING AND ARCHITECTURE

DEPARTMENT OF ELECTRONICS AND ELECTRICAL ENGINEERING

EXPERIMENT NO._3_PSK MODULATION

SUBMITTED BY:

Benavidez, GiovanniJuguilon, JasonManzon, Alvin

SUBMITTED TO:ENGR. JEFFREY P. BERIDA, ECE, ECT

SCORE:

DECEMBER 19, 2014

DIGITAL COMMUNICATIONS10:30-12:00 MTWTH

GROUP NG GWAPO

SCORE:

DECEMBER 19, 2014

DIGITAL COMMUNICATIONS10:30-12:00 MTWTH

GROUP NG GWAPO

Observation:

In this experiment, we tried to again see how PSK (Phase Shift Keying) works and how it is constructed. Unlike FSK, PSK is the same with ASK in terms of carrier frequency count. PSK has only one carrier frequency. Though we have studied that PSK has a number of variations like Quadrature PSK and QAM (Quadrature Amplitude Modulation), we just saw in the diagram a PSK with only one carrier frequency so we then concluded that the PSK we are talking about in this experiment is a Binary PSK. After some brainstorming of what we’re dealing with, we decided to create the circuit diagram which consists of resistors, transistors, potentiometer, op-amp, function generator, and an oscilloscope just like what we did in the ASK and FSK experiment. Again, just like the FSK, we had trouble with the modulated signal since the displayed signal in the oscilloscope did not match what we have studied nor the figure in the laboratory guide. We then realized that maybe; the diagram shown is really a mistake since the modulated signal there was definitely wrong. For the second time, we resorted to researching for an alternate circuit on the internet and again found one. Now, this diagram that we found was much easier to do than the previous one. It also doesn’t have an op-amp. In comparison with the last two digital radio modulation experiments, the PSK is same in some way since the carrier signal also respond to the modulating signal’s logic level. We saw that as transition happens between the modulating signal’s amplitude, the modulated signal becomes out of phase or acquires a phase inversion of 180o with the carrier signal.

Conclusion:

In this experiment, we conclude that a Phase-shift keying (PSK) is a digital modulation scheme that conveys data by changing, or modulating the phase of a reference signal or the carrier wave in proportion to the information signal.Phase reversal always occur in PSK because in this experiment we saw the transition between the modulating signal’s amplitude, the modulated signal becomes out of phase or acquires a phase inversion of 180o with the carrier signal.

SCORE:

DECEMBER 19, 2014

DIGITAL COMMUNICATIONS10:30-12:00 MTWTH

GROUP NG GWAPO