EIE 312 Electronics Engineering Laboratory Experiment: Digital Modulation and Demodulation 1: Curriculum Objectives 1. To understand the Amplitude Shift Keying (ASK) signal. 2. To understand the Frequency Shift Keying (FSK) signal. 3. To understand the Phase Shift Keying (PSK) signal. 4. To implement Digital Receiver 2: Curriculum Theory 1 EIE 312 Electronics Engineering Laboratory 2 EIE 312 Electronics Engineering Laboratory 3 EIE 312 Electronics Engineering Laboratory 4 EIE 312 Electronics Engineering Laboratory 3 Experimental Procedures Experiment 1: ASK modulator 1. Turn on function waveform generator RIGOL DG1062 2. Set CH1 to Sine waveform with frequency 100kHZ by choosing “Freq” on screen menu and input 100KHz. 3. Press Mod button to get modulated signal and choose “Type” on screen menu and then choose “AM”. 4. Press “AM Freq” on screen menu and input 1kHZ and select “AM Depth” and input 100% 5. Press “Shape” on screen menu and choose square. 6. Connect output CH1 OOK signal to Oscilloscope and record the result signal in Table 1. 7. Press “Type” on screen menu and choose ASK 8. Press “ASK Rate” on screen menu and choose 1kHz. 9. Press “ASK Amp” on screen menu and choose 1 Vp-p. 10. Connect output CH1 to Oscilloscope and record the result signal in Table 2. 11. Use AM Demodulator Diode detection AM circuit to demodulate signal from CH1. 12. By using oscilloscope, observe AM I/P, TP1, TP2, TP3, TP4 and Audio O/P signal waveforms. Then record the measured results in table 3. 5 EIE 312 Electronics Engineering Laboratory Experiment 2: FSK modulator 1. Turn on function waveform generator RIGOL DG1062 2. Set CH1 to Square waveform with frequency 20kHZ by choosing “Freq” on screen menu and input 20KHz. 3. Press Mod button to get modulated signal and choose “Type” on screen menu and then choose “FM”. 4. Press “FM Freq” on screen menu and input 1kHZ and select “FM Dev” and input 2kHz. 5. Connect output CH1 to Oscilloscope and record the result signal in Table 4. 6. Press “Type” on screen menu and choose FSK 7. Press “FSK Rate” on screen menu and choose 1kHz. 8. Press “HOP Freq” on screen menu and choose 1kHz. 9. Connect output CH1 to Oscilloscope and record the result signal in Table 5. 10. Use CD4046 FM Demodulation circuit to demodulate signal from CH1. 11. Set TP1 on Demodulation circuit to 20kHz. 12. By using oscilloscope, observe FM I/P, TP2, and Audio O/P signal waveforms. Then record the measured results in table 6. 6 EIE 312 Electronics Engineering Laboratory Experiment 3: PSK modulator 1. Turn on function waveform generator RIGOL DG1062 2. Set CH1 to Sine waveform with frequency 100kHZ by choosing “Freq” on screen menu and input 100KHz. 3. Press Mod button to get modulated signal and choose “Type” on screen menu and then choose “PSK”. 4. Press “PSK Rate” on screen menu and input 1kHZ and select “FM Dev” and input 1kHz. 5. Connect output CH1 to Oscilloscope and record the result signal in Table 7. 6. Use AM Demodulator Product detection AM circuit to demodulate signal from CH1. 7. By using oscilloscope, observe AM I/P, TP1, TP2, TP3, TP4, TP5, TP6, TP7 and Audio O/P signal waveforms. Then record the measured results in table 8. 7 EIE 312 Electronics Engineering Laboratory 4: Measured Results Table 1 Measured results of OOK signal. OOK Table 2 Measured results of ASK signal. ASK Table 3 ASK Demodulation Output Ports AM I/P TP1 TP2 TP3 TP4 Audio O/P Signal Picture 8 EIE 312 Electronics Engineering Laboratory Table 4 Measured results of FM with square audio signal. FM Table 5 Measured results of FSK signal. FSK Table 6 FSK Demodulation Output Port Signal Picture FM I/P TP2 LPF IN Audio O/P Table 7 Measured results of PSK signal. PSK 9 EIE 312 Electronics Engineering Laboratory Table 8 PSK Demodulation Output Port Signal Picture AM I/P TP1 TP2 TP3 TP4 TP5 TP6 TP7 Audio O/P 5: Discussion Questions 1. Describe the different between OOK and ASK. 2. Explain why OOK and ASK can be demodulated with diode detector. 3. Describe the different between FM with square audio input and FSK. 4. Explain how FSK can be demodulated with FM detector. 5. Explain why PSK can be demodulated with AM product detection circuit. 10
