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Digital Communication Lab Experiments

Perform sampling and reconstruction of continuous signal



Objective:

Perform sampling and reconstruction of continuous signal.

Apparatus Required:

  1. Sampling and its reconstruction Kit - DCL 01
  2. Digital Storage Oscilloscope (DSO)
  3. Power supply
  4. Patch cords

Theory

The analog signal can be converted to a discrete time signal by a process called sampling. The sampling theorem for a band limited signal of finite energy can be stated as, ‘’A band limited signal of finite energy, which has no frequency component higher than W Hz is completely described by specifying the values of the signal at instants of time separated by 1/2W seconds.’’ It can be recovered from knowledge of samples taken at the rate of 2W per second. Figure 1.1 shows the complete waveforms of sampling process i.e. Input waveform, clock waveform, sampled waveform and reconstructed waveform.

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model-graph-for-signal-samples-and-reconstruction

Procedure:-

  1. The various blocks are connected as shown in figure 1.2.
  2. Connect the power supply in proper polarity to the kit and & switch it on.
  3. Using the clock selector switch select 8 KHz sampling frequency and using switch SW2 select 50% duty cycle.
  4. The input and output waveforms are measured using CRO.
  5. The procedure above is repeated for sample & hold and flat top sampling
  6. sampling-and-reconstruction-trainer-kit

Observation:The different output waveforms shown in figures 1.3 to 1.4 are observed with the help of CRO and are traced with the help of graph paper.

Conclusion:

The sampling of signal has been performed and it satisfies the Nyquist criteria for reconstruction.

Questions:
  1. 1. Define Nyquist Rate
  2. 2. What is Nyquist interval?
  3. 3. What is Aliasing and how it is reduced?
  4. 4. Compare Natural sampling and Flat Top sampling.

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