To generate the waveform of Amplitude Shift Keying (ASK) signal.

Objective:

To generate the waveform of Amplitude Shift Keying (ASK) signal.

Apparatus Required:

1. Amplitude Shifting Key Kit
2. Cathode Ray Oscilloscope (CRO)
3. Power supply
4. Patch cords

Theory

Amplitude shift keying (ASK) is the simplest digital modulation technique. In this modulation method there is only one carrier which is switched ON/OFF depending upon the input binary sequence to transmit symbol 0 and 1. The binary ASK system was one of the earliest form of digital modulation used in wireless telegraphy. In a binary ASK system binary symbol 1 is represented by transmitting a sinusoidal carrier wave of fixed amplitude A_C and fixed frequency f_Cfor the bit duration T_B where as binary symbol 0 is represented by switching of the carrier for Tb seconds. This signal can be generated simply by turning the carrier of a sinusoidal oscillator ON and OFF for the prescribed periods indicated by the modulating pulse train. For this reason the scheme is also known as on-off shift testing. The ASK signal can be generated by applying the incoming binary data and the sinusoidal carrier to the two inputs of a product modulator. The resulting output is the ASK wave as shown in figure 5.1.

Procedure:-

1. Make the circuit as shown in figure 5.2.
2. Connect the power supply in proper polarity to the kit and & switch it on.
3. The input and output waveforms are measured using CRO.

Observation:The waveforms of CRO shown in figure 5.3 is modulating signal, figure 5.4 (a) is carrier signal and figure 5.4 (b) is PWM signal which are traced with the help of graph paper

Conclusion:The study of amplitude shifting keying has been carried out successfully

Questions:

1. Define Amplitude Shift Keying
2. What are the applications of ASK?
3. What is band-limiting?
4. What is the difference between ASK and OOK?

Precautions:

1. Check the connections before giving the supply.
2. Observations should be done carefully.